tag:theconversation.com,2011:/au/topics/plant-disease-27622/articlesPlant disease – The Conversation2023-11-16T10:12:57Ztag:theconversation.com,2011:article/2163722023-11-16T10:12:57Z2023-11-16T10:12:57ZInsects are spreading a devastating plant disease in Italy – Britain must keep it out<figure><img src="https://images.theconversation.com/files/559575/original/file-20231115-27-9hc0jy.jpg?ixlib=rb-1.1.0&rect=0%2C486%2C3954%2C2134&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Olive trees that have died after becoming infected with _Xylella fastidiosa_.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/dead-olive-trees-xylella-fastidiosa-1471805759">Fabio Michele Capelli/Shutterstock</a></span></figcaption></figure><p>Since 2013, over 20 million olive trees in Italy have succumbed to a <a href="https://www.bbc.com/future/article/20230111-the-super-sniffer-dogs-saving-italys-dying-olive-trees#:%7E:text=With%20its%2060%20million%20olive,which%20were%20several%20centuries%20old">devastating plant disease</a>. The same disease now threatens many more plant species, across several countries, with the same fate. </p>
<p>Our recent <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0291734">research</a> shows that the insect responsible for inadvertently transmitting the bacteria that cause this disease can feed on a vast number of different plant species. These include many herbaceous plants and trees that are commonly grown in gardens, parks and across the wider countryside in Britain.</p>
<p>During spring, gardeners will often wonder why blobs of spit-like foam have suddenly appeared on their favourite plants. Many will think them unsightly, perhaps even taking time to wash them off, only for the foam to appear again the next day. </p>
<p>This “spittle” is produced by an insect, unimaginatively called a spittlebug, whose juvenile stages immerse themselves in the foam in order to stop drying out and to protect themselves from predators.</p>
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<img alt="Meadow spittlebug spittle on the branches of Salix." src="https://images.theconversation.com/files/559572/original/file-20231115-23-8e67h5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559572/original/file-20231115-23-8e67h5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559572/original/file-20231115-23-8e67h5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559572/original/file-20231115-23-8e67h5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559572/original/file-20231115-23-8e67h5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559572/original/file-20231115-23-8e67h5.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559572/original/file-20231115-23-8e67h5.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Spittle produced by a spittlebug.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/aphrophoridae-spittlebugs-family-insects-belonging-order-2000372249">Ihor Hvozdetskyi/Shutterstock</a></span>
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<p>There are several species of spittlebug. But one in particular has been shown to smash several entomological records.</p>
<p>The <a href="https://en.wikipedia.org/wiki/Philaenus_spumarius">meadow spittlebug</a> (<em>Philaenus spumarius</em>) can jump with such force that it accelerates faster than any other animal, equivalent to an extraordinary <a href="https://journals.biologists.com/jeb/article/209/23/4607/16474/Jumping-performance-of-froghopper-insects">550 times</a> that of the Earth’s gravity. Even the toughest astronaut will die if faced with an acceleration <a href="https://www.sciencefocus.com/science/whats-the-maximum-speed-a-human-can-withstand">more than eight times</a> that of gravity.</p>
<p>These insects feed by sucking the sap out of plants. A typical adult meadow spittlebug will drink in and then excrete up to <a href="https://www.nytimes.com/2019/02/19/science/spittlebugs-bubble-home.html">200 times its body weight</a> of fluid per day: another record, and the equivalent of an average human excreting 13,000 litres each day. </p>
<p>Most recently, our research has found that this insect has far broader tastes than any other insect known to science; it can feed on over 1,300 species of plant.</p>
<h2>Why does this matter?</h2>
<p>The meadow spittlebug can transmit a bacterium called <em>Xylella fastidiosa</em> that is potentially deadly for the plants on which it feeds. When the spittlebug uses its syringe-like mouthparts to suck out the plant’s sap, the bacteria can get into the tubes that draw fluids up from the roots. Once there, the bacteria proliferate and block these tubes, starving the plant of water. </p>
<p>The symptoms of infection include scorched or stunted leaves. But, as these symptoms can be confused with several other plant problems, such as dehydration, a definitive diagnosis is difficult. To complicate matters further, some infected plants do not show any symptoms, at least not immediately, making them undetected reservoirs of the bacteria.</p>
<p>The bacteria have caused problems on an epic scale in <a href="https://apsjournals.apsnet.org/doi/epdf/10.1094/PHYTO-08-18-0319-FI">Apulia</a>, Italy’s premier olive-growing region. Entire groves of ancient olive trees have died or have been deliberately destroyed to stop the spread of this devastating plant disease.</p>
<p>The <a href="https://food.ec.europa.eu/plants/plant-health-and-biosecurity/legislation/control-measures/xylella-fastidiosa/database-susceptible-host-plants_en">list of plant species</a> that are known to be susceptible to this disease is long and growing. It already includes 690 species across 88 plant families, encompassing not just trees, but many popular garden plants, important horticultural crops and even some arable crops.</p>
<h2>Spittlebugs in Britain</h2>
<p>As part of our research, we asked members of the British public to send us their sightings of spittle. We received over 17,000 responses. Our results suggest that the insect is widespread in almost all British habitats, including gardens, and on an enormously diverse range of plants.</p>
<p>Fortunately, Britain and most of northern Europe are not yet in the grip of this plant disease. But the ubiquitous distribution of the spittlebug vector and its fondness for such a variety of different plants means that if the bacteria were ever accidentally introduced to Britain, it would be able to spread rapidly with potentially devastating consequences.</p>
<p>Scientists in Britain are anxiously watching for signs of any northward spread of the disease on the European continent. It originated in the Americas and was first detected in Apulia, Italy, in 2013, but it has since been <a href="https://www.efsa.europa.eu/en/topics/topic/xylella-fastidiosa#:%7E:text=Official%20surveys%20carried%20out%20by,How%20do%20plants%20become%20infected%3F">reported</a> in southern France, Spain and Portugal. Certain strains of the disease could certainly tolerate cooler northern temperatures, and their spread may be facilitated by our warming climate. </p>
<p><strong>The global distribution of <em>Xylella fastidiosa</em></strong></p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A world map showing the distribution of xylella fastidiosa bacteria." src="https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=301&fit=crop&dpr=1 600w, https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=301&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=301&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=378&fit=crop&dpr=1 754w, https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=378&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/559561/original/file-20231115-19-64hcev.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=378&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Xylella fastidiosa has not yet been detected in Britain.</span>
<span class="attribution"><a class="source" href="https://gd.eppo.int/taxon/XYLEFA/distribution">EPPO Global Database</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
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<h2>Stopping the spread</h2>
<p>Spittlebugs don’t fly very far so are unlikely to bring the disease into Britain themselves. The most likely entry route would be through plants brought in via the horticultural trade. </p>
<p>Historically, Britain has imported both lavender and olive trees from Italy. However, these plants now have to go through strict importation and quarantine <a href="https://planthealthportal.defra.gov.uk/assets/uploads/UK-Trade-Letter-Feb21-.pdf">controls</a>.</p>
<p>It is critically important that British holidaymakers in Mediterranean countries do not bring home live plant material of any kind. <em>Xylella fastidiosa</em> has not been detected in Britain so far, but the spittlebug’s extraordinarily broad taste in food shows that it would be extremely hard to control if it ever did arrive.</p>
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<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p class="fine-print"><em><span>Alan Stewart received funding from the UK Biotechnology and Biological Sciences Research Council.</span></em></p><p class="fine-print"><em><span>Claire Harkin received funding from the UK Biotechnology and Biological Sciences Research Council</span></em></p><p class="fine-print"><em><span>Vinton Thompson receives funding from the Biotechnology and Biological Sciences Research Council. </span></em></p>The meadow spittlebug can transmit a deadly bacterium – many plants in Britain could be at risk.Alan Stewart, Professor of Ecology, University of SussexClaire Harkin, Research Associate in the Department of Evolution, Behaviour and Environment, University of SussexVinton Thompson, Research Associate in the Division of Invertebrate Zoology, American Museum of Natural HistoryLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2157322023-10-26T13:38:18Z2023-10-26T13:38:18ZA mystery disease hit South Africa’s pine trees 40 years ago: new DNA technology has found the killer<figure><img src="https://images.theconversation.com/files/555224/original/file-20231023-29-u8m533.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">An unidentified fungal killer swept through a South African pine plantation in the 1980s. </span> <span class="attribution"><span class="source">Rodger Shagam</span></span></figcaption></figure><p>In the 1970s and 1980s, pine trees growing in various forestry plantations in South Africa’s Western Cape province began to die in patches. These trees succumbed to a mysterious root disease and the patches expanded gradually. Spontaneous regrowth of seedlings in the patches died dramatically. </p>
<p>As in many other true crime dramas, the finger was initially pointed at the most likely suspect: the root-infecting <em><a href="https://pubmed.ncbi.nlm.nih.gov/28519717/">Phytophthora cinnamomi</a></em>. Its name – plant (phyto) destroyer (phthora) – reveals its power to cause harm; the pathogen is known to cause disease in almost 5,000 different plants.</p>
<p>After further investigation and the collection of many samples, tree pathologists shifted the blame onto the fungus <em>Leptographium serpens</em> (now known as <em>Leptographium alacre</em>). This fungus is well known to be transported by insects and was previously only known in Europe. It was visually identified from the roots of the dying trees. Now it was the prime suspect. </p>
<p>Doubts lingered, though. Most <em>Leptographium</em> species are not known to act as primary disease agents and so <em>L. serpens</em> was most likely not able to cause the disease. Other fungi were also found within the roots of the diseased trees but could not be identified at the time due to a lack of more advanced techniques.</p>
<p>Knowing that the then-available technologies could not provide the complete answer to this mystery, the pathologists took more samples from the dead and dying pine trees, and stored them carefully. The hope was that one day they would have a better idea of the cause of this disease outbreak. </p>
<p>Fast forward to 2023 and a new character enters the mystery: DNA sequencing. This modern technology did what wasn’t possible a few decades ago, allowing our team of molecular mycologists <a href="https://link.springer.com/article/10.1007/s42161-023-01502-1">to identify the real culprit</a>.</p>
<p>This tale is a testament to the ever-evolving nature of scientific inquiry. It reinforces the idea that, in the pursuit of knowledge, no stone should be left unturned and no assumption should be taken for granted. Through a blend of perseverance, technology, and a touch of serendipity, it was possible to solve a decades-old mystery.</p>
<h2>Tracking a killer</h2>
<p>Back in the 1980s the samples were stored in the culture collection of the <a href="https://www.fabinet.up.ac.za">Forestry and Agricultural Biotechnology Institute</a> at the University of Pretoria. In 2020, the samples were revived by a team that included ourselves and several others who recently <a href="https://link.springer.com/article/10.1007/s42161-023-01502-1">published a paper</a> on the topic. </p>
<p>We sequenced the samples’ DNA to reveal their unique genetic code. By comparing this code against genetic databases, it was possible to figure out exactly what was causing the tree disease. And so, more than four decades after the disease was first described, the pathogen was finally identified as <em>Rhizina undulata</em>. <em>L. serpens</em>, the long time primary suspect, was finally exonerated. </p>
<p><em>Rhizina undulata</em> is <a href="https://doi.org/10.1080/00382167.1984.9629524">well known</a> to cause tree disease and death, mainly in Europe. This fungus is known colloquially as the “coffee fire fungus” because the intense heat caused by fires made by campers in a forest to brew coffee activates its dormant spores. This allows it to colonise the roots of conifers, including pines. <em>R. undulata</em> is also well known in South Africa, where it kills many pines in the aftermath of forest fire and when trees are felled to clear a plantation.</p>
<p>What remains a mystery, however, is the trigger that activated this fungus in the Western Cape plantations. No fires were known to have occurred during the relevant time period.</p>
<p>One potential clue to the trigger may lie in the soil in which these trees were planted. Known as Table Mountain sandstone, this soil is sandy and acidic. Acidic soil <a href="https://doi.org/10.1016/S0007-1536(67)80014-7">has been shown</a> in the laboratory to encourage <em>R. undulata</em> growth. This naturally occurring acidity may have been the nudge the pathogen needed to infect the pine trees. It is also possible that the fungus was activated by heat radiating from the quartz rocks that are common in the areas in which the dying trees were planted.</p>
<h2>It pays to be patient</h2>
<p>In the years since the mysterious Western Cape outbreak, <em>R. undulata</em> has become well known to foresters in pine plantations in other parts of South Africa and has done great damage to newly planted trees after fires. These fires can be accidental or due to what is known as slash-burning after trees are harvested. </p>
<p>Identifying <em>R. undulata</em> as the culprit in those (no longer active) Western Cape plantations means scientists have more data that might help to better understand the biology of the fungus – which may lead to better control strategies in the future.</p>
<p>Our work is also a testament to the timeliness of scientific progress and the importance of patience. This story could only be fully unravelled when more advanced techniques were developed. It shows the power of modern technologies to solve historical problems. This underlines the need for continued investment into research and the development of new tools, both in South Africa and worldwide.</p>
<p>Our study also strongly advocates for the preservation of diverse fungal cultures for extended periods of time, regardless of their perceived importance at the time they are collected. The lack of accessible culture collections for lesser-known fungi, in South Africa and internationally, highlights the need for innovative approaches to safeguard these invaluable resources. This shift could revolutionise the study of microbes, opening new avenues beyond traditional species descriptions.</p><img src="https://counter.theconversation.com/content/215732/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andi Wilson receives funding from the National Research Foundation through a Scarce Skills Postdoctoral Fellowship. </span></em></p><p class="fine-print"><em><span>Brenda Wingfield receives funding from South African Department of Science and Innovation. DSI-NRF SARChI chair in Fungal Genomics</span></em></p><p class="fine-print"><em><span>Michael John Wingfield has previously received Grant funding from the South African National Research Foundation and the Department of Science and Innovation as the director of the DSI/NRF Center of Excellence in Tree Health Biotechnology</span></em></p>Through a blend of perseverance, technology, and a touch of serendipity, it was possible to solve a decades-old mystery.Andi Wilson, Postdoctoral fellow, University of PretoriaBrenda Wingfield, Previous Vice President of the Academy of Science of South Africa and DSI-NRF SARChI chair in Fungal Genomics, Professor in Genetics, University of Pretoria, University of PretoriaMichael John Wingfield, Professor, Advisor to the Executive, University of Pretoria, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2020452023-03-20T05:54:09Z2023-03-20T05:54:09ZWhat is myrtle rust and why has this disease closed Lord Howe Island to visitors?<figure><img src="https://images.theconversation.com/files/516283/original/file-20230320-14-9v7ipy.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C4957%2C3287&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Some 70% of the World Heritage-listed Lord Howe Island has been <a href="https://www.theguardian.com/australia-news/2023/mar/17/most-of-lord-howe-island-closed-to-visitors-after-outbreak-of-plant-fungus">closed to non-essential visitors</a> in response to a recurrence of the plant disease myrtle rust.</p>
<p>Myrtle rust, native to South America, was <a href="https://www.dcceew.gov.au/environment/invasive-species/diseases-fungi-and-parasites/myrtle-rust">first detected</a> in Australia on the Central Coast of NSW in April 2010. It is caused by a fungus that belongs to a group of plant pathogens known as the rusts. </p>
<p>Rusts are among the most feared of all plant pathogens. They spread rapidly over thousands of kilometres on wind currents and can cause huge losses in plant production. </p>
<p>For example, wheat rust research over the past 100 years at the University of Sydney has shown clear evidence of wind-borne rust spores travelling from central Africa to Australia. Wheat production losses due to rust have at times totalled <a href="https://www.agriculture.gov.au/abares/research-topics/biosecurity/biosecurity-economics/potential-impact-wheat-stem-rust#">hundreds of millions of dollars</a>. </p>
<p>Myrtle rust rapidly invaded the entire east coast of Australia in the years after it was first detected. It has caused the near extinction of at least three rainforest species, including the native guava (<em><a href="https://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=19162">Rhodomyrtus psidioides</a></em>) and the scrub turpentine (<em><a href="https://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=15763">Rhodamnia rubescens</a></em>). </p>
<p>The disease was detected at Lord Howe Island <a href="https://islandarks.com.au/files/2017/12/I-think-we-dodged-a-bullet-Implementing-a-Rapid-Response-Plan-for-a-Myrtle-Rust-incursion-on-Lord-Howe-Island-in-October-2016.pdf">in 2016, and eradicated</a>. Now it has managed to spread there once again. There are concerns if the disease is left unchecked, it could seriously alter the unique ecology of the island. Lord Howe is home to some 240 native plant species, of which more than 100 are not found anywhere else. </p>
<figure class="align-center ">
<img alt="view of tropical rainforest on Lord Howe Island" src="https://images.theconversation.com/files/516284/original/file-20230320-28-gkim23.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/516284/original/file-20230320-28-gkim23.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/516284/original/file-20230320-28-gkim23.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/516284/original/file-20230320-28-gkim23.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/516284/original/file-20230320-28-gkim23.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/516284/original/file-20230320-28-gkim23.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/516284/original/file-20230320-28-gkim23.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Lord Howe Island has around 100 native plant species that are found nowhere else.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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Read more:
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<h2>How can the disease be controlled?</h2>
<p>Rust diseases in agriculture are controlled by the cultivation of genetically <a href="https://csiropedia.csiro.au/rust-resistance-in-plants/">resistant plants</a>, or by use of fungicides. These fungicides can kill existing recent infections and provide protection for up to four weeks. In other situations, such as horticulture and native plant communities, fungicides are used together with removal and destruction of infected plants.</p>
<p>The 2010 detection of myrtle rust in Australia followed its detection in Hawaii in 2005 and China in 2009. It was later found in New Caledonia (2013) and New Zealand (2017). <a href="https://espace.library.uq.edu.au/view/UQ:13b49a4">Research</a> has shown the same strain – known as the “pandemic strain” – has appeared in all of these countries. Several other strains occur in South America. </p>
<p>It is likely the fungus spread to Lord Howe Island from eastern Australia on wind currents. The especially wet conditions along the east coast of much of Australia in 2022 led to an increase in the disease there. This, in turn, increased rust spore load and hence the chance of long-distance spore dispersal.</p>
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Read more:
<a href="https://theconversation.com/undocumented-plant-extinctions-are-a-big-problem-in-australia-heres-why-they-go-unnoticed-118607">Undocumented plant extinctions are a big problem in Australia – here’s why they go unnoticed</a>
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<p>In addition to being spread on the wind, the rusty coloured spores produced by these fungal pathogens stick readily to clothing. These spores remain viable for at least two weeks under ambient conditions. Several wheat rusts of exotic origin are believed to have been accidentally brought in to Australia on travellers’ clothing from North America and Europe. </p>
<p>The chance of inadvertent spread of myrtle rust on contaminated clothing is why access to Lord Howe island has been restricted since last week. </p>
<p>The second incursion into the island clearly shows how incredibly difficult rust diseases are to manage once they reach a new region. It points to possible recurrences of the disease there in years to come even should current efforts to eradicate it succeed.</p>
<p>On top of the ability of rust diseases to spread rapidly over large distances, a further complication in controlling myrtle rust is it infects a wide range of native plants. Some of these species hold great cultural significance and/or are endangered. </p>
<p>Endemic species of the myrtle plant family <a href="https://www.britannica.com/plant/Myrtaceae">Myrtaceae</a> that are dominant in many of the plant communities on Lord Howe Island are highly vulnerable to myrtle rust infection. Of critical concern are two species that occur only on the island: the mountain rose (<em>Meterosideros nervulosa</em>) and the rainforest tree scalybark (<em>Syzigium fullagarri</em>). The rust infects young leaves and also flowers, where it causes sterility.</p>
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Read more:
<a href="https://theconversation.com/lets-show-a-bit-of-love-for-the-lillipilly-this-humble-plant-forms-the-worlds-largest-genus-of-trees-and-should-be-an-australian-icon-191080">Let's show a bit of love for the lillipilly. This humble plant forms the world's largest genus of trees – and should be an Australian icon</a>
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<h2>Australia brings expertise to the battle</h2>
<p>Australia has some of the best plant pathologists in the world and has long been a leader in controlling rust diseases in agriculture. This expertise, combined with world-leading scientists in the ecology of Australian native plants, has enabled solid progress in understanding myrtle rust in the Australian environment. Australian scientists have joined hands with New Zealand scientists to boost efforts to control the pathogen in both countries. </p>
<p>Research is also under way at the University of Sydney and Australian National University to develop new DNA-based diagnostics to allow rapid identification of the different strains of the pathogen. These tests are especially important given only one strain of myrtle rust occurs in the Asia-Pacific and Oceania regions.</p>
<p>The success of managing the impact of myrtle rust on the region’s iconic flora against a backdrop of climate change will rely heavily on undertaking the research needed to gain a much better understanding of this damaging plant pathogen. Recognising this, staff at the University of Sydney have convened a conference for June 21-23 this year. It will bring together myrtle rust experts to exchange their latest research findings and identify priority areas for research.</p><img src="https://counter.theconversation.com/content/202045/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Park does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Spread by the wind, the fungal rusts are among the most feared of all plant diseases. A 2016 myrtle rust outbreak on Lord Howe Island was contained, but now its unique plants are again under threat.Robert Park, Judith and David Coffey Chair in Sustainable Agriculture, Plant Breeding Institute, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2004282023-03-07T13:43:36Z2023-03-07T13:43:36ZPancakes won’t turn you into a zombie as in HBO’s ‘The Last of Us,’ but fungi in flour have been making people sick for a long time<figure><img src="https://images.theconversation.com/files/513212/original/file-20230302-18-uldpy1.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1198%2C628&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A human fungal zombie from the TV show 'The Last of Us.'</span> <span class="attribution"><a class="source" href="https://imgix.bustle.com/uploads/image/2023/1/20/2c922756-5f33-430d-801b-995eec7dc0d1-the-last-of-us.jpg?w=1200&h=630&fit=crop&crop=faces&fm=jpg">Liane Hentscher/HBO</a></span></figcaption></figure><p>In the HBO series “<a href="https://www.hbo.com/the-last-of-us">The Last of Us</a>,” named after the popular video game of the same name, the flour supplies of the world are contaminated with a fungus called <em>Cordyceps</em>. When people eat pancakes or other foods made with that flour, the fungi grow inside their bodies and turn them into zombies. </p>
<p>As a <a href="https://scholar.google.com/citations?user=5iZjEckAAAAJ&hl=en&oi=ao">food scientist</a>, I study the effect of processing on the quality and safety of fruits and vegetables, including the flour used to make pancakes. While no one is going to turn into a zombie from eating pancakes in real life, flour is often contaminated with fungi that can produce mycotoxins that make people sick. Proper processing and cooking, however, can generally keep you safe. </p>
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<figcaption><span class="caption">‘The Last of Us’ is premised on a pandemic that brings the world to an apocalyptic collapse.</span></figcaption>
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<h2>How common is fungi in flour?</h2>
<p>People have been eating bread made from wheat for <a href="https://www.bbc.com/news/science-environment-44846874">approximately 14,000 years</a> and cultivating wheat for <a href="https://sustainablefoodtrust.org/news-views/a-brief-history-of-wheat/">at least 10,000 years</a>. In 1882, “<a href="https://doi.org/10.7717%2Fpeerj.12346">drunken bread disease</a>” was first documented in Russia, where people reported dizziness, headache, trembling hands, confusion and vomiting after eating bread. Long before that, Chinese peasants were reporting that eating pinkish wheat – a key sign of infection with a mold called <em>Fusarium</em> – caused them to feel ill. Clearly, fungi have been making people sick for a long time.</p>
<p>Wheat, corn, rice and even fruits and vegetables can be infected with fungi as they grow in the field. In “The Last of Us,” an epidemiologist theorizes that climate change is causing the fungus to mutate so it can infect humans. The unfortunate reality is that fungi have become more of a problem in recent years as <a href="https://doi.org/10.3389/fcimb.2018.00060">warmer temperatures</a> encourage their growth. </p>
<p><a href="https://doi.org/10.1111/jfs.12422">A 2017 study</a> found that over 90% of wheat and corn flour samples in Washington, D.C., contained live fungi, with <em>Aspergillus</em> and <em>Fusarium</em> the predominant types of mold in wheat flour. <em>Fusarium</em> grows on wheat in the field and can cause a common agricultural plant disease called <a href="https://ahdb.org.uk/knowledge-library/fusarium-and-microdochium-in-cereals">fusarium head blight</a>, or scab. </p>
<p>Farmers use <a href="https://open.alberta.ca/publications/fusarium-head-blight-of-barley-and-wheat">multiple techniques</a> to reduce this devastating plant disease, including implementing crop rotation, using resistant varieties and fungicides and minimizing irrigation during flowering. After harvesting, they sort the grains to remove contaminated wheat before grinding them into flour. While sorting removes most of the contaminated wheat, small amounts of fungi can still make it into the flour.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Pink wheat stalks infected with fusarium head blight" src="https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513399/original/file-20230303-29-cz1zd4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Wheat infected with fusarium head blight have a characteristic pink hue.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/fusarium-ear-blight-fusarium-head-blight-fhb-or-royalty-free-image/1358429685">Tomasz Klejdysz/iStock via Getty Images Plus</a></span>
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<h2>Killing microorganisms in flour</h2>
<p>The good news is that most fungi and other microorganisms <a href="https://www.ars.usda.gov/ARSUserFiles/60701000/FoodSafetyPublications/p328.pdf">die at 160-170 degrees Fahrenheit</a> (71-77 degrees Celsius). Pancakes are typically cooked to an internal temperature of <a href="https://www.lafujimama.com/oven-baked-pancake/">190-200 F</a> (88-93 C). Other cakes and breads are cooked to internal temperatures <a href="https://blog.thermoworks.com/bread/baked-good-doneness-temps/">anywhere from 180 to 210 degrees Fahrenheit</a> (82-99 C). So, unlike in “The Last of Us,” as long as you bake or fry your dough, you’ll have killed the fungi.</p>
<p>The problem comes when people eat the flour without cooking it first, such as by consuming raw cookie dough or “licking the bowl clean.” Both raw egg and raw flour can contain microorganisms that make people sick. The microorganisms that public health officials are most worried about are <a href="https://www.cdc.gov/foodsafety/communication/ecoli-and-food-safety.html"><em>E. coli</em></a> and <a href="https://www.cdc.gov/foodsafety/communication/salmonella-food.html"><em>Salmonella</em></a>, dangerous pathogens that can cause severe illness. </p>
<p>Most people don’t realize that the flour they buy at the store is raw flour that still contains live microorganisms. Flour is rarely commercially treated to be safe to eat raw because consumers almost always cook flour-based foods. While consumers can also attempt to heat-treat raw flour at home, <a href="https://ag.purdue.edu/stories/home-kitchen-heat-treated-flour-doesnt-protect-against-foodborne-illnesses-purdue-food-scientist-says/">this isn’t recommended</a> because the flour may not be spread thinly enough to kill all of the microorganisms.</p>
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<a href="https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Microscopy image of _Aspergillus_" src="https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513408/original/file-20230303-20-m292l6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption"><em>Aspergillus</em> is one of the predominant molds found in wheat flour.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/aspergillus-under-the-light-microscopic-view-for-royalty-free-image/1332594729">tonaquatic/iStock via Getty Images Plus</a></span>
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<p>Some fungi and microorganisms can create spores, which are like seeds that help them survive adverse conditions. These spores can survive cooking, drying and freezing. There are even <a href="https://www.smithsonianmag.com/smart-news/bread-was-made-using-4500-year-old-egyptian-yeast-180972842/">4,500-year-old yeast spores</a> that have been reawakened and made into bread. These fungal spores rarely cause serious illness in people, except in those with <a href="https://doi.org/10.1101%2Fcshperspect.a019273">weakened immune systems</a>.</p>
<p><a href="https://doi.org/10.3390%2Fmicroorganisms5030037">Chemicals can be added to food</a> to stop fungal growth. These additives include sorbates, benzoates and propionates. However, you almost never see these additives in flour or pancake mix because fungi can’t grow in a dry powder. The fungi either grew on the wheat in the field or on the bread after it is baked. For that reason, you may see these additives in bread but not in a powdered mix.</p>
<h2>Mycotoxins</h2>
<p>The biggest risk from fungi is not that it will grow inside our bodies, but that it will grow on wheat or other foods and produce <a href="https://doi.org/10.5487%2FTR.2019.35.1.001">chemicals called mycotoxins</a> that can cause severe health problems. When wheat is harvested and ground into flour, mycotoxins can get mixed in. </p>
<p>Unfortunately, while normal cooking can kill the microorganisms, it <a href="https://doi.org/10.5487%2FTR.2019.35.1.001">doesn’t destroy the mycotoxins</a>. Eating mycotoxins can cause problems ranging from hallucinations to vomiting and diarrhea to cancer or death. Some of the <a href="https://doi.org/10.1111/jfs.12422">common mycotoxins</a> found in grain include aflatoxins, deoxynivalenol, ochratoxin A and fumonisin B.</p>
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<a href="https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Moldy pastry on a plate" src="https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/513410/original/file-20230303-22-5r5j15.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">It might be best to leave that moldy bread alone.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/moldy-inedible-spoiled-food-pasty-with-mold-in-a-royalty-free-image/1167797155">Yulia Naumenko/Moment via Getty Images</a></span>
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<p>The oldest known case of mycotoxin poisoning is recorded as a <a href="https://doi.org/10.1021/acs.jafc.6b04494">disease called ergotism</a>. Ergotism was mentioned in the Old Testament and has been reported in Western Europe since A.D. 800. It has even been suggested that the <a href="https://www.vox.com/2015/10/29/9620542/salem-witch-trials-ergotism">Salem witch trials</a> were caused by an outbreak of ergotism that led its victims to hallucinate, though many have disputed this idea. Wheat is <a href="https://doi.org/10.1007/s11356-021-12671-w">less likely</a> than other grains to have dangerous mycotoxins, which is why some have proposed that declining mortality in 18th-century Europe, <a href="https://doi.org/10.1017/s0025727300034116">especially in England</a>, was due to the switch from a rye-based diet to a wheat-based diet.</p>
<p>Ultimately, you don’t need to worry about eating those pancakes. Farmers use many techniques to minimize fungal growth and remove moldy grain, and the government keeps a close eye on mycotoxin levels during crop production and storage. Just make sure you cook your bakery products before eating, and don’t eat anything that has started to mold.</p><img src="https://counter.theconversation.com/content/200428/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sheryl Barringer does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Raw flour at the store still contains live microorganisms. And while cooking can kill the fungi, it doesn’t destroy any illness-causing mycotoxins that might be present.Sheryl Barringer, Professor of Food Science and Technology, The Ohio State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1844232022-08-16T12:29:28Z2022-08-16T12:29:28ZFrom watering via ice cubes to spritzing with hydrogen peroxide – 4 misguided plant health trends on social media<figure><img src="https://images.theconversation.com/files/470313/original/file-20220622-25-3avjqj.jpg?ixlib=rb-1.1.0&rect=0%2C11%2C7377%2C4885&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The internet has become a new player in plant care advice.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/two-female-friends-watching-online-gardening-royalty-free-image/1295397619">Kanawa_Studio/iStock via Getty Images Plus</a></span></figcaption></figure><p>The internet is full of advice on just about everything, including plant care.</p>
<p>As the <a href="https://plant.lab.uconn.edu/">director of a plant diagnostic laboratory</a> and expert on plant medicine, I help people manage their plants’ health. Here are four trends I’ve seen online recently that have stood out as being especially misleading or potentially damaging to plants. </p>
<h2>Watering orchids and other plants with ice cubes</h2>
<p>Multiple sites claim ice cubes can be used to give orchids a “just right” amount of water. The fact is tropical plants hate cold temperatures. Leaving <a href="http://www.ladybug.uconn.edu/FactSheets/house-plants---growing-.php">ice near an orchid’s roots may damage them</a>.</p>
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<p>Nearly all houseplants, including orchids, will prefer lukewarm or room temperature water, about 70 degrees Fahrenheit (21 degrees Celsius). Use fact sheets from educational institutions and reputable organizations to determine the correct amount of water and watering schedule for the types of plants you’re growing, and then set a reminder on your phone. </p>
<p>Use a potting medium that drains well and quickly. For orchids, <a href="https://www.aos.org/orchids/orchid-care/what-is-the-best-potting-media.aspx">a mix of bark chips and sphagnum moss is much better</a> than 100% soil or coco coir. </p>
<h2>‘No Mow May’</h2>
<p>Many campaigns have sprung up recently promoting “<a href="https://beecityusa.org/no-mow-may/">No Mow May</a>.” The idea is to delay regular mowing for the month of May to provide more feeding sites for pollinators, which are trying to shore up calories after their winter hibernation.</p>
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<p>Unfortunately, this practice usually does not benefit pollinators and could damage your lawn’s health. Here’s why:</p>
<p>Mowing more than 30% of a grass leaf at once is never a good idea. Grasses depend on their blades to photosynthesize and meet their energy needs. When more than 30% is lost at once, the plants may not have enough remaining leaf surface area to photosynthesize properly.</p>
<p>Overgrown lawns have overgrown root systems, which require more energy. Failure to provide it leads to <a href="https://hgic.clemson.edu/mowing-height-matters/">increased susceptibility to disease</a>, poor water management and potential collapse. Such damage is pretty much unavoidable after a monthlong “no mow” period. </p>
<p>Few lawns actually contain enough flowers to be beneficial to pollinators, anyway. For many people, the “perfect lawn” is an unwavering green carpet. But that uniformity is useless to bees and other pollinators that require <a href="https://www.epa.gov/pollinator-protection/what-you-can-do-protect-honey-bees-and-other-pollinators">pollen and nectar that other plants can provide</a>. </p>
<p>It’s great to <a href="https://www.epa.gov/pollinator-protection/what-you-can-do-protect-honey-bees-and-other-pollinators">prioritize pollinator health</a>, but the “no mow” trend is best implemented in prairie, field and wetland environments, where there is a lot of plant diversity and flowering plants. </p>
<p>If you’re looking to support pollinator health in your own yard, <a href="https://www.nwf.org/NativePlantFinder">plant native wildflowers</a> that pollinators will actually want to visit. Most require less water and management compared to grass lawns. Replace your entire lawn or even a small strip. Any amount of lawn replaced is beneficial – and will save you water and money. </p>
<p>Make sure not to mow the wildflowers until they’ve finished flowering. A wildflower patch usually only needs to be cut once or twice a year. Mowing after the last frost in early spring will spread the previous year’s seeds and <a href="https://extension.psu.edu/planting-pollinator-friendly-gardens">provide a home for insects to spend the winter</a>. </p>
<h2>Using hydrogen peroxide to ‘cure’ plant diseases</h2>
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<p>Hydrogen peroxide <a href="https://pubchem.ncbi.nlm.nih.gov/compound/Hydrogen-peroxide">does sterilize surfaces and can reduce bacteria and some fungi</a>. But the rapid reaction that gives hydrogen peroxide its sterilizing properties occurs almost immediately after coming in contact with other compounds. This does not permit hydrogen peroxide to move throughout a plant.</p>
<p>So most pathogens – the organisms that cause disease – will not be affected if they are in a plant’s tissues rather than on its exterior. Applying hydrogen peroxide excessively or improperly may even <a href="https://pubchem.ncbi.nlm.nih.gov/compound/Hydrogen-peroxide">make plant health issues worse</a> by drying surfaces and killing beneficial microbes. </p>
<p>While there is certainly a time and place for sterilizing surfaces in plant care – like with your pruners and propagation tools – the best defense against plant diseases is proper care. </p>
<p>Water your plants only when necessary and provide proper light and nutrition. Research what your plant likes best from educational institutions or other reputable sources. Routine pruning to increase airflow, proper plant spacing, avoiding single-crop planting and crop rotation are just some examples of chemical-free techniques to <a href="https://ipm.cahnr.uconn.edu/">reduce plant stress and decrease disease susceptibility</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A woman holds up her cell phone to photograph the roots of a plant." src="https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470069/original/file-20220621-15-io6uku.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Virtual diagnosis?</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-holding-and-taking-photo-of-potato-crop-royalty-free-image/1322163523">Sanja Radin/E+ via Getty Images</a></span>
</figcaption>
</figure>
<h2>Diagnosing diseases using phone apps</h2>
<p>Many apps exist that use photographs submitted by the user to identify plant diseases and offer solutions. </p>
<p>The truth is, to diagnose most plant diseases, a scientist needs to culture plant tissue to correctly identify pathogens. Only after an accurate diagnosis <a href="https://apsjournals.apsnet.org/journal/pdis">can they recommend management solutions</a>. I have a pretty strong opinion here, since disease identification is what I do every day. Plant symptoms that accompany one disease may be practically identical to those of another. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Photos of four different plants with curled leaves labeled herbicide exposure, virus, insect feeding and fungal infection." src="https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/472617/original/file-20220705-4524-eyxbyp.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The same symptom can be caused by very different problems.</span>
<span class="attribution"><span class="source">Bugwood.org</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>For example, herbicide exposure, viruses, insect feeding and fungal infections can all cause twisted and deformed leaves. To properly diagnose an issue, the plant’s own history, location, site history, time of year and other factors need to be considered before I can take a guess as to what may be contributing to symptoms. </p>
<p>Don’t rely on an app to guess at what disease your plant may have – and don’t act on bogus recommendations. Instead, reach out to your local university diagnostic lab or extension office for support. </p>
<p>Not sure where to go? Start with the <a href="https://www.npdn.org/lab_directory">National Plant Diagnostic Network’s lab directory</a>. Many, including mine, offer free consultations and recommendations. If you end up submitting a sample to a diagnostic lab, most are affordable – my lab’s fee is US$20 – and will be worthwhile, especially when you consider the cost of replacing the plant with something that could eventually have the same issue.</p><img src="https://counter.theconversation.com/content/184423/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nick Goltz (UConn Plant Diagnostic Laboratory) receives funding from the USDA-NIFA and the state of Connecticut. </span></em></p>Plant care advice abounds on TikTok, Twitter, Instagram and YouTube – but not all of it is good. A plant expert debunks four common recommendations.Nick Goltz, Assistant Extension Educator and Director, UConn Plant Diagnostic Laboratory, University of ConnecticutLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1848182022-07-11T18:37:15Z2022-07-11T18:37:15ZSpace agriculture boldly grows food where no one has grown before<figure><img src="https://images.theconversation.com/files/473090/original/file-20220707-26-kg2bsz.jpeg?ixlib=rb-1.1.0&rect=0%2C0%2C1908%2C1916&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Satellite imagery monitors environmental changes to inform agricultural decisions. Agricultural patterns are distinctly visible in this near-vertical false colour infrared photography of farmland south of Khartoum, Sudan.</span> <span class="attribution"><a class="source" href="https://images.nasa.gov/details-sts066-84-038">(JSC/NASA)</a></span></figcaption></figure><iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/space-agriculture-boldly-grows-food-where-no-one-has-grown-before" width="100%" height="400"></iframe>
<p>Whether to spend money on outer space exploration or to apply it to solve serious problems on Earth, like climate change and food shortages, is a contentious debate. But one argument in favour of space exploration highlights benefits that do, in fact, help study, monitor and address serious concerns like climate change and food production.</p>
<p>As access to space increases, the potential for terrestrial benefits directly tied to space exploration grow exponentially.</p>
<p>For example, agriculture has been improved significantly through the application of space-based advances to terrestrial challenges. It is now increasingly likely that food items have been produced with the assistance of space-based technologies, <a href="https://spinoff.nasa.gov/Spinoff2020/cg_2.html">like freeze-dried foods</a>, or through the use of <a href="https://nasaharvest.org/news/measuring-crop-characteristics-space">crop monitoring from space-based observatories</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a hand holds a growing small plant with a chart behind it" src="https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=513&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=513&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473089/original/file-20220707-20-4q2cod.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=513&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Dwarf wheat photographed aboard the International Space Station in April 2002.</span>
<span class="attribution"><a class="source" href="https://images.nasa.gov/details-0300227">(NASA/MSFC)</a></span>
</figcaption>
</figure>
<h2>Monitoring farmlands</h2>
<p><a href="https://doi.org/10.1007/978-3-319-33438-7">Satellite monitoring</a> is arguably the most realized benefit of space for farming. Like mindful eyes in the sky, satellites watch over the farmlands across the globe day and night. Specialized sensors on relevant satellites (for example, <a href="https://landsat.gsfc.nasa.gov/data/">NASA’s Landsat</a>, <a href="https://www.esa.int/Enabling_Support/Operations/Envisat">the European Space Agency’s Envisat</a> and <a href="https://www.asc-csa.gc.ca/eng/satellites/radarsat/">the Canadian Space Agency’s RADARSAT</a>) monitor various parameters relevant to agriculture. </p>
<p>Sensors monitoring soil moisture can tell us when and how fast soils are drying, helping direct more efficient irrigation on a regional scale. Weather satellites help predict <a href="http://www.nasa.gov/feature/goddard/2021/nasa-at-your-table-the-space-agency-s-surprising-role-in-agriculture">drought, floods, precipitation patterns and plant disease outbreaks</a>. </p>
<p>Satellite data helps us <a href="https://www.smithsonianmag.com/innovation/predict-famine-before-strikes-180954945/">predict food insecurity threats or crop failures</a>.</p>
<h2>Plant science</h2>
<p>It’s not only lifeless machines that dwell in space. Humans have managed to survive and <a href="https://astrobotany.com/a-brief-history-of-plant-habitats-in-space/">grow plants in low-Earth orbit aboard several spacecraft and stations</a>. Space is the ultimate “<a href="https://www.esa.int/Science_Exploration/Space_Science/Extreme_space/Surviving_extreme_conditions_in_space">harsh environment</a>” for life to exist in, including plants, due to such novel stressors as cosmic radiation and lack of gravity.</p>
<p>Space biologist Anna-Lisa Paul describes plants as being able to “reach into their genetic toolbox and remake the tools they need” to adapt to the novel environment of space. The new tools and behaviours <a href="https://doi.org/10.1016/j.isci.2022.104687">expressed by plants under spaceflight conditions</a> could be used to solve challenges facing crops in Earth’s changing climate.</p>
<p>Researchers at NASA sent cotton seeds to the International Space Station to understand how cotton roots grow in the absence of gravity. The findings of the research will help develop <a href="https://www.agriculture.com/crops/growing-cotton-in-space-helps-identify-sustainable-production-practices">cotton plant varieties with a deeper root system to access and absorb water more efficiently from soil in drought-prone areas</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/LwwDIP36eb8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Space biologist Anna-Lisa Paul describes how plants respond to stress, and what that can teach us.</span></figcaption>
</figure>
<h2>Farming technologies</h2>
<p>Soon, humans will go to <a href="https://www.nasa.gov/specials/60counting/future.html">the moon</a> and <a href="https://www.nasa.gov/directorates/spacetech/6_Technologies_NASA_is_Advancing_to_Send_Humans_to_Mars">eventually to Mars</a>. While there, astronauts will have to grow their own food. </p>
<p>Space agencies have been working on specialized systems that provide the conditions necessary for plant cultivation in space. These systems are containers that can control the internal environment and grow plants without soil under LED lights. NASA’s research in <a href="https://spinoff.nasa.gov/indoor-farming">controlled environment systems to grow plants was foundational in developing the modern-day vertical farm sector</a> — indoor farms that grow crops in stacks without soil under the purple haze of LEDs.</p>
<p>Now a burgeoning industry, vertical farms are churning out enormous volumes of fresh and healthy leafy crops with a fraction of the water and nutrients that would be used in land-based farm systems. Vertical farms can be set up within cities, right where the demand lies, thereby cutting the need for long-distance transport. </p>
<p>As crops are grown indoors in controlled environments, vertical farms can substantially reduce the reliance on herbicides and pesticides, while recycling water and preventing nutrient runoff.</p>
<h2>Space agriculture, Earth benefits</h2>
<p>Considering the constraints of space, crop production techniques need to be more energy-efficient and require minimal human input. Crops need to also be nutrition-rich, with the ability to withstand high-stress environments. These features are also desirable for crops on Earth.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="plants grow in stacked rows under purple uv light" src="https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/473080/original/file-20220707-26-zkqyrs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hydroponic and vertical farming was developed to allow crops to grow without soil or sunshine.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Scientists are developing a more <a href="https://doi.org/10.1038/s41467-021-26238-3">resource-efficient potato crop where the whole plant can be consumed, including roots, shoots and fruits</a>. Such crops will play a pivotal role in addressing food and nutritional security on Earth and in space.</p>
<p>Space exploration has served as a major driver for technological advances. The renewed interest in space can only benefit agriculture here on Earth by providing new opportunities to improve agriculture. Innovations that are quite literally out-of-this-world can provide us tools to tackle food production under the looming threats posed by global climate change.</p><img src="https://counter.theconversation.com/content/184818/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas Graham receives funding from OMAFRA, NSERC, Canadian Space Agency, Commercial partners on government grants. </span></em></p><p class="fine-print"><em><span>Ajwal Dsouza does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Technologies being developed for growing food in space have contributed to advances in agriculture and crops on Earth.Ajwal Dsouza, PhD Candidate, Environmental Sciences, University of GuelphThomas Graham, Assistant Professor, Environmental Sciences, University of GuelphLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1586322021-04-21T13:20:20Z2021-04-21T13:20:20ZResearchers unlock the secrets of fungal viruses: why it matters<figure><img src="https://images.theconversation.com/files/395660/original/file-20210419-23-gnlcsr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Fungal viruses have been important in reducing the impact of fungal diseases on chestnuts in Europe.</span> <span class="attribution"><span class="source"> Aygul Bulte/Shutterstock</span></span></figcaption></figure><p>In the past year the world has been overwhelmed with rapidly emerging, important and fascinating information regarding SARS CoV-2, the virus that causes COVID-19. The pace of learning has been astounding, not just for the general public but for virus experts.</p>
<p>There are millions of viruses out there, including many that don’t directly infect animals or humans. Some are better understood than others. Among the least studied are viruses that infect fungi. But it’s becoming increasingly important to address this gap: fungal viruses can cause <a href="https://www.jstor.org/stable/3760453?seq=1">tremendous damage</a>, for instance by hitting agricultural outputs. Researchers estimate that such viruses destroy <a href="https://pubmed.ncbi.nlm.nih.gov/31345409/">up to 30% of crop products</a>. This has huge implications for food security.</p>
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Read more:
<a href="https://theconversation.com/why-maize-is-causing-trade-tensions-between-kenya-and-its-neighbours-156797">Why maize is causing trade tensions between Kenya and its neighbours</a>
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<p>In the past few decades the technology needed to sequence and study fungal viruses has improved in leaps and bounds. This, coupled with a rising understanding among scientists that fungal viruses have very real and frequently negative consequences, hopefully means we’re at the dawn of a new era when it comes to understanding fungal viruses. </p>
<p>Until recently there were only a few types of viruses easily detected in fungi. But this has begun to change. In a <a href="https://doi.org/10.1038/s41598-021-86343-7">recent paper</a> with colleagues we used the latest RNA sequencing technology to identify a whole host of single stranded RNA viruses in the notorious plant pathogenic genus <em>Armillaria</em>. We also confirmed previous studies which had showed that species in this genus did not contain double stranded RNA viruses. Knowing this is important because the first step in managing any disease is identifying and understanding the causal agent.</p>
<p>This illustrates how technology is allowing researchers to better understand fungal viruses, and come up with ways to manage them. </p>
<h2>Varied viruses</h2>
<p>The first fungal viruses were discovered in the 1940s in <em><a href="https://www.mushroomexpert.com/agaricus_bisporus.html">Agaricus bisporus</a></em>, the most common commercially cultivated mushroom. This viral infection causes a malady known as “<a href="https://pubmed.ncbi.nlm.nih.gov/20822315/">La France disease</a>” and results in malformed fruiting bodies (mushrooms) and yield loss. </p>
<p>Certain fungal viruses, when properly understood and harnessed, can become helpful and useful. Some, for instance, make the fungi they infect less aggressive, a phenomenon called hypovirulence. One example is the hypovirus CHV1, which reduces virulence in the tree pathogen <em>Cryphonectria parasitica</em>, one of the most devastating of all plant-killing fungi. It decimated natural populations of the American chestnut tree, beginning in the early 1900s. CHV1 was first discovered in Europe in the 1960s after people noticed that European chestnut trees affected by <em>C. parasitica</em> had begun to recover. They did not suffer the same devastation that befell the American species.</p>
<p>Hypovirulent viruses have been of great interest to researchers because of their potential as biocontrol agents of fungi that cause serious plant diseases. But to work out which fungal viruses are uniformly harmful and which might be harnessed for biocontrol, scientists first have to study the viruses’ genetic makeup.</p>
<p>New DNA sequencing technologies have heightened the ease with which fungal viruses can be studied. This has led to a <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0219207">huge increase</a> in the number of fungal viruses that are being characterised. Researchers have recently used <a href="https://www.mdpi.com/2076-2607/8/11/1680">the latest technology</a> to focus on the earlier-diverging lineages of the fungal kingdom. They found that just over 20% of the microorganisms they studied contained RNA viruses. These viruses also included novel lineages not previously recorded. </p>
<p>All of this deepens our understanding of how these viruses emerge and function – which makes combating them potentially easier in future.</p>
<p>Scientists are also starting to better understand how fungal viruses move between species. Some recently discovered fungal viruses are most closely related to viruses that were thought to infect plants only. It is <a href="https://doi.org/10.1073/pnas.1714916114">speculated</a> that these viruses may have been acquired from plants in a manner similar to the way bat viruses have in some cases adapted to become human pathogens. It is also possible that fungal viruses might infect plants, although little is as yet known regarding this possibility.</p>
<h2>Much more to learn</h2>
<p>As fungal viruses are increasingly studied, the great breadth of their diversity is becoming clear. And their role in the biology of fungi will likewise become more evident. </p>
<p>I have been studying fungal viruses for decades. My PhD, completed nearly 30 years ago, focused on fungal viruses, specifically those of the common brewer’s yeast, <em>Saccharomyces cerevisiae</em>, which is used in brewing and baking. I am convinced that many new opportunities, especially associated with the biological control of plant and human diseases caused by fungi, will emerge from the study of fungal viruses.</p><img src="https://counter.theconversation.com/content/158632/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brenda Wingfield receives research funding from the National Research Foundation and benefits indirectly from research grants from a number of industries with a focus on tree/plant health . </span></em></p>Technology is allowing scientists to better understand fungal viruses, with the aim of managing them more effectively.Brenda Wingfield, Previous Vice President of the Academy of Science of South Africa and DSI-NRF SARChI chair in Fungal Genomics, Professor in Genetics, University of Pretoria, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1394232020-06-10T14:55:09Z2020-06-10T14:55:09ZWhy it’s so critical to continuously monitor and manage plant diseases<figure><img src="https://images.theconversation.com/files/338785/original/file-20200601-95059-hxbdbm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hands-on monitoring is key to fighting many plant diseases.</span> <span class="attribution"><span class="source">Edwin Remsberg/VWPics/Universal Images Group via Getty Images</span></span></figcaption></figure><p>Most of us understand the <a href="https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance-publications?healthtopics=b6bd35a3-cf4f-4851-8e80-85cb0068335b&publishingoffices=aeebab07-3d0c-4a24-b6ef-7c11b7139e43&healthtopics-hidden=true&publishingoffices-hidden=true">critical importance of monitoring</a> the spread of diseases. And it is as important for plant diseases as it is for humans. </p>
<p>Plant disease epidemics are often hidden from view, unlike human viral disease outbreaks. Yet food and forest production systems, as well as native environments around the world, are just as threatened by emerging epidemics. That is why the UN has made 2020 the <a href="https://www.fabinet.up.ac.za/index.php/iyph2020">International Year of Plant Health</a>.</p>
<p>It is estimated that pests and pathogens destroy between <a href="https://www.nature.com/articles/s41559-018-0793-y">10% and 40% of food production globally</a>. </p>
<p>There are ways to deal with this problem, starting with <a href="https://www.ippc.int/en/">biosecurity and plant health management systems</a>. But this is yet another system that’s been put under tremendous pressure by the emergence of COVID-19. Under restrictions on human movement – necessary to curb the virus’ spread – the field and laboratory work that are crucial for surveillance and management of plant diseases has been severely curtailed. </p>
<p>Research and specialist services delivered by universities, for example, have in <a href="https://theconversation.com/lockdowns-and-research-what-we-lost-and-what-we-stand-to-gain-138355">many cases temporarily closed or are operating at minimal levels</a>. Missing even a few months could mean missing a key moment in a pest’s life cycle and a chance to intervene and slow its further spread. The pressure on government funding that is required to sustain these systems is also threatening to bring these programmes to a standstill.</p>
<p>Plant diseases require as much attention now as ever to ensure that food systems are in place in the next season. There are also serious implications for forestry and <a href="https://theconversation.com/tree-diseases-can-change-entire-landscapes-and-must-be-taken-seriously-135743">the environment more broadly</a>.</p>
<h2>Under threat</h2>
<p>Plant health epidemics can be caused by viruses, bacteria, fungi, nematodes or insects. Many of these organisms originate in one part of the world and <a href="https://link.springer.com/article/10.1007%2Fs10530-016-1081-x">rapidly spread to threaten food crops or trees globally</a>. They often jump from a <a href="https://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(05)00149-7?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0169534705001497%3Fshowall%3Dtrue">host</a> plant on which they do not cause significant epidemics, to a different plant that does not have resistance to them. </p>
<p>Global biosecurity systems are under pressure to deal with the scale of the problem. For example, trade in plants and plant parts is known to be a major pathway of spread of pests and pathogens. But even well-resourced <a href="https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/110198">systems in the US</a> cannot cope with the inspection of billions of plants traded annually. The <a href="https://link.springer.com/article/10.1007/s10530-017-1488-z">problem is bigger in developing economies</a>, including <a href="https://bit.ly/3eDPNE2">many in Africa</a>, because of a lack of capacity. </p>
<p>Biosecurity relies on four things: prevention (at port of entry); preparedness (early detection, diagnostics and control); response (to contain and eradicate or manage plant pests and diseases); and recovery (systems for regulating eradication, management or restoration). </p>
<p>Unfortunately, insect and fungal pests can spread naturally across borders. Once a pest is introduced into one country a whole continent’s food, forestry and native systems <a href="https://theconversation.com/alien-animals-and-plants-are-on-the-rise-in-africa-exacting-a-growing-toll-78684">could be threatened</a>. An example is the fall armyworm, which was first reported in West Africa in 2016 and spread across the continent, <a href="https://theconversation.com/why-its-hard-to-control-the-fall-armyworm-in-southern-africa-72890">reaching South Africa one year later</a>. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/339414/original/file-20200603-130912-hn8prz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/339414/original/file-20200603-130912-hn8prz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/339414/original/file-20200603-130912-hn8prz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/339414/original/file-20200603-130912-hn8prz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/339414/original/file-20200603-130912-hn8prz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/339414/original/file-20200603-130912-hn8prz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/339414/original/file-20200603-130912-hn8prz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A fall armyworm on a maize crop in Vihiga, Kenya.</span>
<span class="attribution"><span class="source">SIMON MAINA/AFP via Getty Images</span></span>
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</figure>
<p>Estimates in 2017 put potential losses in maize production in Africa to this pest at between US$ 2.4-6.2 billion. Such production losses could lead to food insecurity in many African countries.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/alien-animals-and-plants-are-on-the-rise-in-africa-exacting-a-growing-toll-78684">Alien animals and plants are on the rise in Africa, exacting a growing toll</a>
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<h2>Plant health crisis examples</h2>
<p>There are hundreds, if not thousands, of pests and pathogens threatening African countries already. Here are just three examples:</p>
<p>On a main food crop: <a href="https://apsjournals.apsnet.org/doi/10.1094/PHYTO-12-14-0367-FI">Maize lethal necrosis disease</a> is caused by the joint infection of more than one virus and can completely devastate a maize crop. The disease <a href="https://apsjournals.apsnet.org/doi/10.1094/PHYTO-12-14-0367-FI">first emerged in Kenya</a> in 2011; it has since spread to surrounding countries with devastating yield losses. It is critically important to track its spread, identify outbreaks and attempt to eradicate or restrict its movement. Identification requires highly specialised laboratory analysis to confirm the identity of the viruses. </p>
<p>In plantation forestry: The <a href="https://www.fabinet.up.ac.za/index.php/tpcp/forest-threats/sirex-noctilio">Sirex woodwasp</a> is native to Europe, but has caused billions of US Dollars damage since it was introduced in New Zealand around 1900 and eventually around the world. A biological control programme that uses a parasitic nematode to sterilise the wasp is widely applied, and has <a href="https://www.businessinsider.co.za/this-tiny-worm-has-saved-south-africas-forestry-industry-r404-million-2018-8">saved the South African forestry industry hundreds of millions of Rand</a>. This programme depends on thorough national monitoring of the wasp infestation levels and the timely release of the biological control nematode. </p>
<p>On native, urban and agricultural trees: The <a href="https://www.fabinet.up.ac.za/index.php/pshb">Polyphagous Shot Hole Borer</a> is a tiny ambrosia beetle that introduces a fungal symbiont into trees on which its offspring will feed. The beetle originates from South East Asia, but is spreading around the world. In South Africa it has been recorded from more than a 100 different tree species, and fruit crops such as Avocado. It can <a href="https://theconversation.com/a-tiny-beetle-and-its-deadly-fungus-is-threatening-south-africas-trees-92050">kill some mature trees in a matter of months</a>. </p>
<p>Tracking of spread, physical removal of infested trees and the development of biological control are all <a href="https://theconversation.com/trees-in-south-africa-are-under-attack-why-its-proving-hard-to-manage-130804">urgent needs</a> and require specialist knowledge and laboratory support for identification. Monitoring also includes citizen science initiatives in urban areas, and requires researchers to travel to confirm new infestations.</p>
<p>All of this has been set back by restrictions on human movement designed to contain the spread of COVID-19. Researchers must now work out how to catch up, and plan for the coming years in which the virus is likely to continue being a global concern.</p>
<h2>What should be done?</h2>
<p>Firstly, an assessment is needed of the impact of the original COVID-19 responses on plant health biosecurity systems, so as to plan for coming months and years. We would argue that in future, existing biosecurity systems must remain in full operation. Field surveillance and management of potential biological threats to plant production systems and ecosystems cannot be relaxed or restricted. This can be done safely, in line with global guidelines around protection from the virus.</p>
<p>Secondly, it is critical to recognise that the future of food security is linked across borders. Weak biosecurity in one country threatens neighbouring countries and whole continents. It is important to review regulations and their implementation to secure food supply, industries and the environment. Countries also need strong research funding and capacity.</p><img src="https://counter.theconversation.com/content/139423/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bernard Slippers receives research funding from various Agriculture and Forestry related industry and government bodies. </span></em></p><p class="fine-print"><em><span>Jolanda Roux works for Sappi</span></em></p><p class="fine-print"><em><span>Marinda Visser does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Plant diseases require as much attention now as ever to ensure that food systems are in place in the next season. There are also serious implications for forestry and the environment more broadly.Bernard Slippers, Director of the Forestry and Agricultural Biotechnology Institute and Future Africa, University of PretoriaJolanda Roux, Extra-ordinary Professor, Forestry and Agricultural Biotechnology Institute, University of PretoriaMarinda Visser, Director: Strategic Projects and Partnerships in Agriculture - Innovation Africa@UP, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1308042020-02-04T10:35:48Z2020-02-04T10:35:48ZTrees in South Africa are under attack. Why it’s proving hard to manage<figure><img src="https://images.theconversation.com/files/313303/original/file-20200203-41481-1ve06g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>More than two years have passed since the detection of what is arguably the most damaging tree pest ever to arrive in South Africa: the <a href="https://doi.org/10.1007/s13313-018-0545-0">polyphagous shot hole borer</a> (<em>Euwallacea fornicatus</em>). The beetle kills trees and there are no proven remedies. </p>
<p>The beetle is now present in nearly all parts of the country and in more than <a href="https://www.fabinet.up.ac.za/index.php/pshb">100 tree species</a>. </p>
<p>An invasion of this magnitude should have elicited a rapid response and the development of a strategic action plan. But that hasn’t happened. South Africa has never had to deal with a tree-killing pest of this importance before. In addition, the country has limited resources and there has been confusion about which government department should take responsibility. As a result, there hasn’t been a coordinated response to deal with the pest.</p>
<p>The tiny polyphagous shot hole borer beetle is 2mm in length and native to Southeast Asia. It has a symbiotic relationship with three species of fungi, including <em>Fusarium euwallaceae</em>. The fungus is a food source for the beetle and its larvae, but can kill susceptible host trees. </p>
<p>The list of host trees in South Africa continues to grow. Not all of these support the whole life cycle of the polyphagous shot hole borer. But it’s been found to breed in <a href="https://www.fabinet.up.ac.za/index.php/pshb">25 species</a> (both exotic and indigenous trees). </p>
<p>The greatest impact has been in urban environments such as <a href="https://www.timeslive.co.za/sunday-times/lifestyle/home-and-gardening/2019-06-01-10-things-to-know-about-the-bug-thats-mercilessly-killing-sas-trees-en-masse/">Johannesburg</a>. It has been detected on backyard avocado and roadside weedy acacias, but not yet in commercial orchards or plantations. The only commercial crop it’s been detected on is pecan trees. </p>
<p>In <a href="https://doi.org/10.1094/PDIS-03-12-0276-PDN">California</a> and <a href="https://link.springer.com/article/10.1007%2Fs12600-012-0223-7">Israel</a>, polyphagous shot hole borer went on to damage the avocado industry as well as trees in natural ecosystems. There are concerns that this could happen in South Africa too.</p>
<p>But it hasn’t yet been declared an agricultural emergency plant pest and no formal response has been triggered. Based on the Israeli and Californian experiences, it could clearly still pose a threat to economically important crops in South Africa.</p>
<p>The proactive thing to do would be to list the beetle as an emergency plant pest.</p>
<h2>Gaps in the system</h2>
<p>South Africa is good at managing pests in agricultural settings. This falls under the Department of Agriculture, Land Reform and Rural Development, specifically <a href="https://www.daff.gov.za/daffweb3/Branches/Agricultural-Production-Health-Food-Safety/Plant-Health/Pest-Surveillance">Plant Health Early Warning Systems</a>. Where a pest is deemed an emergency plant pest, the South African Emergency Plant Pest Response Plan provides for a rapid response to prevent establishment, spread and coordination of communication between government agencies, academia and plant industry professionals. </p>
<p>For example, detection of the <a href="https://www.daff.gov.za/daffweb3/Branches/Agricultural-Production-Health-Food-Safety/Food-Import-Export-Standards/Fall-armyworm">Fall Army Worm</a> (<em>Spodoptera frugiperda</em>), a quarantine pest of maize and sorghum, triggered a rapid and coordinated response overseen by the national government. Provincial departments, academic institutes and industry stakeholders have been working together on aspects ranging from monitoring, training and diagnostics to pesticide registration, legislation and enforcement.</p>
<p>The Department of Environment, Forests and Fisheries provides for listing of invasive alien species that threaten biodiversity, through the <a href="https://www.sanbi.org/documents/nemba-invasive-alien-species-regulations/">National Environmental Management: Biodiversity Act</a>. </p>
<p>The pest risk analysis for polyphagous shot hole borer (the process by which listing is facilitated) has been submitted, but the listing is yet to be finalised.</p>
<p>The country’s laws also place a “duty of care” on all land owners (private and public) to control invasive species on their land. They also require all levels of government – from municipal through to national – to develop monitoring, control and eradication plans for land under their control. </p>
<p>But systems designed for the agricultural or natural environment sector aren’t helping the management of a beetle that’s wreaking havoc on trees in towns and cities. </p>
<p>This is also clear in how the country manages <a href="http://academic.sun.ac.za/cib/">invasive species</a>. It does this well when it comes to weeds and larger animals. But forest pests are barely represented. </p>
<p>Another major challenge is that the borer beetle is particularly hard to <a href="https://edis.ifas.ufl.edu/fr422">manage</a> because of its mating system, wide range of hosts and ability to survive in felled wood for many months. On top of this, heavily infested reproductive hosts become “reservoirs” of beetles, threatening the health of adjacent trees. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-spread-of-shothole-borer-beetles-in-south-africa-is-proving-tough-to-control-102996">The spread of shothole borer beetles in South Africa is proving tough to control</a>
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<p>Current best practice recommends removal of heavily infested trees in which beetles are breeding. <a href="https://ucanr.edu/sites/pshb/id-mgmt/disposal/">Infested wood</a> should be disposed of appropriately at designated dumping sites to reduce the risk of spread. </p>
<p>But in the absence of a national strategy to guide municipalities, responses to the pest have varied. <a href="https://www.capetowninvasives.org.za/shot-hole-borer">Cape Town</a> has perhaps led the way with a coordinated city response to the recent invasion in Somerset West. In conjunction with its Invasive Species Unit, the city has developed a management protocol. As one of the more recent areas to be invaded, it’s perhaps had the benefit of being able to better prepare for the arrival of this pest and learn from the experiences of other municipalities. </p>
<p>Research from <a href="https://apsjournals.apsnet.org/doi/10.1094/PDIS-10-17-1569-RE">California</a> suggests chemical control may have an application in protecting individual high value trees. But this shouldn’t be seen as a <a href="https://www.businesslive.co.za/bd/national/science-and-environment/2019-08-13-no-magic-cure-to-stop-the-beetle-that-is-killing-trees-countrywide/">silver bullet</a>.</p>
<p>In South Africa’s case, various research efforts are underway to shed more light on the beetle and its impact. For example, a unit at the University of Pretoria, the Forestry and Agricultural Biotechnology Institute has been involved in surveillance and monitoring of the pest. </p>
<p>The multi-disciplinary and multi-institutional <a href="https://www.fabinet.up.ac.za/index.php/research-groups/pshb-research-network">Polyphagous Shot Hole Borer Research Network</a> has recently been established. With members from ten different academic institutes, the network aims to align and coordinate research efforts by researchers from institutions across the country. </p>
<p>Now with funding made available by the Department of Environment, Forests and Fisheries, further research can be conducted under the framework of this network, to underpin science and data-based management advice.</p>
<p>But a great deal still remains to be done. South Africa would do well to reflect on how it’s responded so far.</p><img src="https://counter.theconversation.com/content/130804/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Trudy Paap receives funding from the National Research Foundation and the Tree Protection Co-operative Progamme.</span></em></p>A tree-killing beetle that invaded South Africa two years ago and wreaked havoc in the country’s towns and cities still hasn’t been declared an emergency plant pest.Trudy Paap, Postdoctoral Fellow Forestry and Agricultural Biotechnology Institute, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1165672019-05-07T11:47:14Z2019-05-07T11:47:14ZAsh dieback: one of the worst tree disease epidemics could kill 95% of UK’s ash trees<figure><img src="https://images.theconversation.com/files/273033/original/file-20190507-103049-1v1nw1y.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5746%2C3819&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The lonely Malham Ash at dawn in Yorkshire Dales National Park.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/lonelieness-dawn-iconic-malham-ash-growing-712440229?src=UrvNDViHS8LahEZq_wEQ6g-1-8">PhilMacDPhoto/Shutterstock</a></span></figcaption></figure><p>Ash dieback – a fatal disease of Britain’s native ash trees (<em>Fraxinus excelsior</em>) – is one of the worst tree disease epidemics the UK has ever seen. The disease is caused by a fungus that originated in Asia but is thought to have <a href="https://www.nature.com/articles/s41559-018-0548-9">arrived in Europe on exotic plants</a> in the early 1990s, where it has devastated native ash species which have very little natural immunity.</p>
<p>Ash dieback has since spread ferociously throughout Europe due to airborne spores and trade in ash saplings which have no visual symptoms of the disease. In 2012, <a href="https://www.bbc.co.uk/news/uk-scotland-scotland-politics-20254790">the disease was confirmed in the UK</a> and later shown to have been imported on saplings to multiple sites across the country. It is now found throughout the UK. There’s no cure and <a href="https://www.forestresearch.gov.uk/tools-and-resources/pest-and-disease-resources/chalara-ash-dieback-hymenoscyphus-fraxineus/">very few trees show signs of long-term resistance</a>.</p>
<p>The environmental impacts of the disease are likely to last a long time, but as <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(19)30331-8">our new paper explains</a>, they’ll also carry a shockingly high economic cost.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/273040/original/file-20190507-103085-1mgn0x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273040/original/file-20190507-103085-1mgn0x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273040/original/file-20190507-103085-1mgn0x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273040/original/file-20190507-103085-1mgn0x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273040/original/file-20190507-103085-1mgn0x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273040/original/file-20190507-103085-1mgn0x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273040/original/file-20190507-103085-1mgn0x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Wilting leaves are a symptom of dieback – a fungal infection of ash trees.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Chalara_ash_dieback_-_symptoms_-_29.jpg">Courtesy The Food and Environment Research Agency (Fera), Crown Copyright</a></span>
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<p>There are 150m mature ash trees in the UK, making ash one of the most common native tree species in the country. We estimate that ash dieback will kill at least 95% of ash trees and cost the UK economy £15 billion – a cost one third greater than that reported from <a href="https://www.ncbi.nlm.nih.gov/pubmed/12523706">the foot-and-mouth disease outbreak in 2001</a>. Half of this cost will arise in the next ten years.</p>
<p>Putting a monetary value on ecosystem services – the beneficial effects that trees provide for people and the economy - helps people understand the scale of the problem. Roughly £10 billion worth of ecosystem services will be lost as ash trees disappear.</p>
<p>Losing these services will have wide-ranging consequences. Less carbon dioxide will be absorbed from the atmosphere and the risk of flooding will increase. Studies have also shown that losing trees from a community is linked to <a href="https://www.sciencedirect.com/science/article/pii/S0749379712008045">poorer physical and mental health</a> among the people who live there. Tackling climate change calls for an enormous effort to plant trees but ash dieback will rob the UK of using this valuable native species.</p>
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<img alt="" src="https://images.theconversation.com/files/273036/original/file-20190507-103082-aluwsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/273036/original/file-20190507-103082-aluwsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273036/original/file-20190507-103082-aluwsc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273036/original/file-20190507-103082-aluwsc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273036/original/file-20190507-103082-aluwsc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273036/original/file-20190507-103082-aluwsc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273036/original/file-20190507-103082-aluwsc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Ash trees often border roads and paths in the UK – making their removal more difficult.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/row-ash-trees-fraxinus-excelsior-along-690651211?src=-BdH19USNkNd2Lkcg1gWpw-1-6">Photodigitaal.nl/Shutterstock</a></span>
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<p>Clearing up dead and dying ash trees will carry another major cost, particularly where they present a risk to human safety. Stricken ash trees are prone to shedding limbs or collapsing completely, either directly due to the ash dieback fungus or a secondary pathogen such as honey fungus infecting the weakened tree. <a href="https://www.trees.org.uk/Trees.org.uk/media/Trees-org.uk/Documents/Conference17/WED-04-Jon-Stokes.pdf">More than 4m ash trees line Britain’s roadsides</a>. Felling these will be expensive and involve road closures and power and communications outages as work is carried out. </p>
<p>Ash trees in towns and cities will need the same treatment. A major national replanting effort could reduce the total cost of losing ash trees by as much as £2.5 billion, but a diverse mixture of native species will need to be planted to improve the resilience of new trees to pests and diseases. Replanting should also be carefully managed to ensure habitats are connected throughout the landscape.</p>
<h2>Rising from the ashes</h2>
<p>Exotic disease is not a problem limited to ash trees. People move plants – and unwittingly, their diseases – around the world at rates that far outstrip natural disease spread. The international trade in plants, travel and climate change are all contributing to an acceleration in the rate of new tree diseases emerging and spreading. </p>
<p>More tree pests and diseases have arrived in Britain <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/710719/tree-health-resilience-strategy.pdf">in the last 40 years</a> than at any time before then. As more native species are threatened, the effects will combine and multiply. Losing most ash trees will be bad enough, but what if the UK loses oak next, or birch? The idea of a landscape largely devoid of trees is appalling, and the economic costs incalculable.</p>
<p>People aren’t powerless in this story though. The science is clear that the largest pathway for spreading tree diseases is the <a href="https://www.ncbi.nlm.nih.gov/pubmed/24233727">international trade in live plants and soil</a>. Stricter controls on this trade could better protect our trees for generations to come.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/273043/original/file-20190507-103060-1rsndaj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273043/original/file-20190507-103060-1rsndaj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273043/original/file-20190507-103060-1rsndaj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273043/original/file-20190507-103060-1rsndaj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273043/original/file-20190507-103060-1rsndaj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273043/original/file-20190507-103060-1rsndaj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273043/original/file-20190507-103060-1rsndaj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The international trade in trees has helped spread diseases to places where native species have little genetic resistance.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/russia-samara-april-2017-seedlings-various-1053950906?src=8JHP7vyTouiDMknGhGXV8A-1-14">Tramp57/Shutterstock</a></span>
</figcaption>
</figure>
<p>Most countries prioritise the value of trade in live plants over the risks to their native flora. Our paper shows that the value of the annual trade in ash saplings amounted to only 2% of the estimated cost of ash dieback.</p>
<p>The costs of restricting trade and improving border controls have long been used to block the introduction of stronger biosecurity measures for plants. But we now know that the costs of diseases like ash dieback have been wildly underestimated and this new evidence demands an urgent rethink.</p>
<p>The health of native trees, in fact of all wildlife, needs to be valued far more highly. We must recognise not only the essential benefits that the natural environment provides for us, but how severe the consequences are for society when new pathogens are spread.</p><img src="https://counter.theconversation.com/content/116567/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nick Atkinson is a Fellow at the Centre for Ecology and Hydrology. He is also an employee of the Woodland Trust.</span></em></p>A new study has calculated the tremendous cost of ash dieback to the UK economy.Nick Atkinson, Research Fellow in Spatial Ecology, UK Centre for Ecology & HydrologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1099822019-01-17T11:36:31Z2019-01-17T11:36:31ZCoffee: 60% of wild species are at risk of extinction due to climate change<figure><img src="https://images.theconversation.com/files/254313/original/file-20190117-32825-1mio4p5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/cup-coffee-smoke-beans-burlap-sack-582329227?src=LF-5eBaFLgxMgQ8xUzJmeQ-1-29">Amenic181/Shutterstock</a></span></figcaption></figure><p>Is your morning coffee an espresso or a skinny latte? Is it from a darkly roasted French or Italian blend? If it’s a high quality brew, it’s almost certainly made with beans from the Arabica species (<em>Coffea arabica</em>), which is known for its finer flavours. Examples would be Javan coffees, Ethiopian sidamo, and the expensive Jamaican blue mountain.</p>
<p>If you’ve stirred together an instant blend, it’s probably from a different species, Robusta (<em>Coffea canephora</em>), <a href="https://www.cirad.fr/en/our-research/tropical-supply-chains/coffee/plant-and-uses">known for its harsher taste</a>. But there are <a href="https://doi.org/10.1111/j.1095-8339.2006.00584.x">more than 100 species of coffee</a> in the wild. All produce similar beans that you could make a recognisable coffee drink from.</p>
<p>Robusta is sometimes openly mixed with Arabica in commercial products – and is often <a href="https://doi.org/10.1016/j.foodchem.2017.12.034">secretly used to adulterate</a> “100% Arabica” products, too. A third species, <em>Coffea liberica</em>, native to west and central Africa, is widely grown for local use in tropical countries, but is not globally traded because of its more bitter taste. </p>
<p>A fourth species <em>Coffea eugenoides</em> bred with Robusta to give rise to Arabica, a crossbreed. Another 38 closely related species are known or assumed to have <a href="http://advances.sciencemag.org/content/5/1/eaav3473">fertile pollen transfer with commercial coffees</a>.</p>
<p>There are a further 82 species which are more distantly related to the commercial breeds, but scientists could interbreed them with commercial coffees in a lab. All these coffee relatives can help enhance the genetic diversity of commercial coffee species, making them more adaptable to changes in their environment.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/254131/original/file-20190116-163274-1u0u5re.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/254131/original/file-20190116-163274-1u0u5re.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254131/original/file-20190116-163274-1u0u5re.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254131/original/file-20190116-163274-1u0u5re.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254131/original/file-20190116-163274-1u0u5re.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254131/original/file-20190116-163274-1u0u5re.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254131/original/file-20190116-163274-1u0u5re.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Arabica coffee beans growing in Colombia.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/closeup-coffee-fruit-farm-plantations-manizales-325255673?src=DfSQ0C3IhkISjNQ_X49WKg-1-6">Fotos593/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Dark days ahead for coffee</h2>
<p>Climate change is <a href="https://theconversation.com/climate-change-is-causing-havoc-for-global-coffee-yields-25685">threatening global coffee yields</a> as changing temperatures and rainfall patterns affect plant growth. The changing climate may also be leaving plants <a href="https://doi.org/10.1098/rstb.2015.0458">more vulnerable to disease</a>.</p>
<p>All major commercial coffee growing countries have been badly affected by the fungal disease “<a href="http://www.bbc.com/future/story/20171106-the-disease-that-could-change-how-we-drink-coffee">coffee leaf rust</a>”, which spread across Africa and into Asia during the early 20th century, then to South America, becoming entrenched globally by the turn of the millennium.</p>
<p>The <a href="https://worldcoffeeresearch.org/work/applied-rd-coffee-leaf-rust/">Central American coffee rust outbreak</a> that began in the 2011-2012 harvest season affected 70% of farms in the region, resulting in over 1.7m lost jobs and US$3.2 billion in damage and lost income.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/climate-change-is-causing-havoc-for-global-coffee-yields-25685">Climate change is causing havoc for global coffee yields</a>
</strong>
</em>
</p>
<hr>
<p>Robusta varieties used for the instant blends have been key to <a href="https://doi.org/10.1007/s12571-015-0446-9">developing resistance to coffee leaf rust</a> in Arabica varieties through cross breeding. As climate change and disease risks escalate, wild coffee species offer a crucial resource for maintaining the world’s coffee supply. Arabica has tightly limited geographic ranges in which it grows well and Robusta, while resistant to leaf rust, is vulnerable to <a href="https://www.researchgate.net/publication/277890144_Compendium_of_coffee_pests">other diseases</a>.</p>
<p><a href="http://advances.sciencemag.org/content/5/1/eaav3473">A recent study</a> led by the UK’s Kew Royal Botanic Gardens set the value of this variety in context: over 60% of coffee species are <a href="https://www.iucnredlist.org/">threatened with extinction</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/254546/original/file-20190118-100267-chbbjx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/254546/original/file-20190118-100267-chbbjx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=485&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254546/original/file-20190118-100267-chbbjx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=485&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254546/original/file-20190118-100267-chbbjx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=485&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254546/original/file-20190118-100267-chbbjx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=610&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254546/original/file-20190118-100267-chbbjx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=610&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254546/original/file-20190118-100267-chbbjx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=610&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Leaf rust (<em>Hemileia vastatrix</em>) on a coffee plant.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Hemileia_vastatrix#/media/File:Hemileia_vastatrix.jpg">Howard F. Schwartz/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The authors explained that wild relatives of coffee are already used as local substitutes for globally traded commercial crops. They offer different climatic tolerance ranges and disease resistance traits that can help ensure global coffee production continues to meet demand. </p>
<p>But coffee species are particularly vulnerable to extinction because they occur in a small numbers of small geographic ranges – such as pockets of <a href="https://theconversation.com/ethiopias-vulnerable-tropical-forests-are-key-to-securing-future-of-wild-coffee-56516">wild Arabica populations</a> between certain altitude ranges in the Ethiopian highlands.</p>
<p>Wild coffee species – and wild varieties of the commercial species – are almost all <a href="https://doi.org/10.1126/sciadv.aav3473">in decline</a> due to competition for land use and overharvesting of the coffee plant for timber or firewood. A number of wild coffee relatives haven’t been spotted for many decades and may be extinct. </p>
<p>One species, the <a href="http://globaltrees.org/threatened-trees/trees/cafe-marron/">cafe marron</a>, from the remote island of Rodrigues in the Indian Ocean, was known from only one sighting in 1877. A century later, a schoolboy drew an “unusual” tree while exploring and showed it to a teacher. They recognised it as a surviving cafe marron. The sole surviving specimen of that wild coffee has inspired wider forest conservation on Rodrigues. It is also being cultured in lab collections at Kew.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/254324/original/file-20190117-32825-1ys2vrf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/254324/original/file-20190117-32825-1ys2vrf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/254324/original/file-20190117-32825-1ys2vrf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/254324/original/file-20190117-32825-1ys2vrf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/254324/original/file-20190117-32825-1ys2vrf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/254324/original/file-20190117-32825-1ys2vrf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/254324/original/file-20190117-32825-1ys2vrf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Genetic diversity should also be considered in sustainability campaigns like Fairtrade.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/city-ljubljana-slovenia-europe-3-january-318452198?src=BAgreBZ5FY9FkOhNJtFwAg-1-13">Peacepix/Shutterstock</a></span>
</figcaption>
</figure>
<p>Sadly, there may be less hope for other species. Coffee seeds don’t store well, unlike wild relatives of other crops such as wheat or maize. So we can’t rely on <a href="https://theconversation.com/after-svalbard-why-safety-of-world-seed-vaults-is-crucial-to-future-food-security-79586">storage in seed banks</a> to conserve coffee diversity and resilience. Freezing plant matter in labs or growing samples in test tubes might be an alternative, but not one that has been explored beyond existing commercial strains.</p>
<p>Preserving different coffee varieties in botanic gardens isn’t really viable for protecting genetic diversity either. Coffee species readily fertilise each other, “<a href="https://doi.org/10.1007/s10722-012-9898-3">contaminating</a>” the resource you’re trying to conserve.</p>
<p>While some experts suggest we <a href="https://worldcoffeeresearch.org/work/global-coffee-conservation-strategy/">preserve coffee diversity in collections</a>, the Kew Gardens study argues that the sustainability of coffee depends on conservation of these species where they grow, in protected areas and working with communities throughout their native distribution in Africa and Asia.</p>
<p>Conserving genetic diversity should be included in existing approaches for sustainable coffee production, such as <a href="https://theconversation.com/food-security-how-fairtrade-helps-level-the-playing-field-for-small-producers-70937">Fair Trade</a> and <a href="https://www.rainforest-alliance.org">Rainforest Alliance</a> certifications. Ensuring the continuity of the coffee trade means protecting the ecosystems coffee comes from and the livelihoods of people across the <a href="https://theconversation.com/wheres-that-bean-been-coffees-journey-from-crop-to-cafe-30207">bean to coffee cup economy</a>.</p>
<p>We can also expect new flavours and even coffees with naturally low or zero caffeine content. Naturally caffeine-free Indian Ocean island cafe marron anyone?</p><img src="https://counter.theconversation.com/content/109982/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adam Moolna does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>There are over 100 species of wild coffee, but only a few supply the world’s morning caffeine kick. Sadly, climate change and disease could be about to change that.Adam Moolna, Teaching Fellow in Environment and Sustainability, Keele UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1029962018-11-02T14:46:30Z2018-11-02T14:46:30ZThe spread of shothole borer beetles in South Africa is proving tough to control<figure><img src="https://images.theconversation.com/files/243643/original/file-20181102-83626-104s5yq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Shutterstock</span> </figcaption></figure><p>A tiny tree-killing beetle with the awkwardly long name of Polyphagous Shothole Borer was detected in South Africa for the first time <a href="https://theconversation.com/a-tiny-beetle-and-its-deadly-fungus-is-threatening-south-africas-trees-92050">last year</a>. It’s now attacking and inserting its deadly <a href="https://www.tandfonline.com/doi/full/10.3852/13-066">fungal ally</a>, <em>Fusarium euwallaceae</em>, in a wider array of tree species across a much wider geographical area.</p>
<p>The beetle was initially discovered in a Botanical Garden on the country’s east coast. It has since been detected along the southern Cape coast line as well as in several inland urban areas. The number of tree species attacked in South Africa has also risen alarmingly. It currently stands at more than <a href="https://www.fabinet.up.ac.za/pshb">80</a>, 35 of which are native.</p>
<p>The shothole borer, which is native to Southeast Asia, has the potential to affect fruit, nut and wood production, but also to permanently change urban landscapes and natural forest ecosystems. This has happened on <a href="https://www.californiaavocadogrowers.com/growing/pshbkshb/pshbkshb-fact-sheets">farms</a>, in <a href="https://landscapearchitecturemagazine.org/2018/03/13/the-tiny-menace/">suburbs</a> and <a href="https://peerj.com/articles/2141/">in forests along river valleys</a> in California.</p>
<p>The South African government has started to take steps to manage the problem. The <a href="http://www.daff.gov.za/daffweb3/Branches/Agricultural-Production-Health-Food-Safety/Plant-Health/Pest-Surveillance">Department of Agriculture, Fisheries and Forestry</a> has set up a steering committee to guide national efforts. It’s made up of representatives from various government departments, the forestry and agriculture sectors, as well as academics, arborists, and nurserymen. </p>
<p>The major challenge with the beetle infestation is that the insect is crossing the boundaries between agriculture, commercial forestry, natural forests, and urban trees. Never in the country’s history has any insect attacked and killed trees in all these sectors. The protection of trees in the different sectors is typically dealt with by different government departments, namely Department of Agriculture, Fisheries and Forestry, the <a href="https://www.environment.gov.za/">Department of Environmental Affairs</a>, and municipalities. But given the beetle’s unusual behaviour, routine action plans aren’t enough to curb the problem.</p>
<h2>The threat to South Africa’s trees</h2>
<p>Of the <a href="https://www.fabinet.up.ac.za/pshb">80 species</a> of trees under attack in South Africa, about 20 are reproductive hosts in which the beetle inoculates its fungus and then multiplies. These trees pose a serious risk to the environment around them as they become a source of infestation. </p>
<p>In the remaining 60 host species the beetle also inserts the fungus, but it doesn’t reproduce in them. Although some of these trees may eventually die, they don’t pose a threat to the other trees around them.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/236995/original/file-20180918-158234-1l5l28h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/236995/original/file-20180918-158234-1l5l28h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=322&fit=crop&dpr=1 600w, https://images.theconversation.com/files/236995/original/file-20180918-158234-1l5l28h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=322&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/236995/original/file-20180918-158234-1l5l28h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=322&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/236995/original/file-20180918-158234-1l5l28h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=405&fit=crop&dpr=1 754w, https://images.theconversation.com/files/236995/original/file-20180918-158234-1l5l28h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=405&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/236995/original/file-20180918-158234-1l5l28h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=405&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A London plane tree in Johannesburg, infested by the Shothole Borer.</span>
<span class="attribution"><span class="source">Supplied by author.</span></span>
</figcaption>
</figure>
<p>The species of ornamental and street trees most affected in South Africa’s cities are the London plane, Boxelder, Japanese maple, Chinese maple, English oak and Liquidamber. Several streets of maples and liquidamber have died in some cities, and large, old English oaks and plane trees have been severely affected in some areas.</p>
<p>During countrywide surveys conducted by our team at <a href="https://www.fabinet.up.ac.za">FABI</a>, we found several fruit trees (peach, olive, grapevine, guava, fig) infested in urban areas. However, the only commercial crop that’s affected at present are pecan nut trees on farms in the Northern Cape. </p>
<p>In <a href="https://link.springer.com/article/10.1007%2Fs12600-012-0223-7">Israel</a> and <a href="https://doi.org/10.1094/PDIS-03-12-0276-PDN">California</a> the beetle caused substantial damage in avocado orchards, and although South African orchards are closely monitored by FABI team members, we have only detected it on a single backyard avocado tree in Johannesburg. Similarly, we found it on roadside wattle and eucalyptus trees, but so far the pest hasn’t been detected in commercial Eucalyptus, wattle or pine plantations.</p>
<p>In our opinion the most significant threat, but also the most difficult to predict and manage, is to South Africa’s <a href="https://www.fabinet.up.ac.za/pshb">native tree species</a> such as coral trees, wild olives, yellow woods and Natal figs.</p>
<h2>Managing the problem</h2>
<p>California has been battling the beetle problem for the last 10 years. A recent visit to the area helped us to establish what practical actions have been taken to bring the problem under control. </p>
<p>An effective public awareness campaign was launched, informing residents and local governments about the beetle and its impact. Municipalities removed reproductive host trees, most of which were going to die anyway. The state also introduced legislation preventing <a href="https://www.dontmovefirewood.org/pest_pathogen/polyphagous-shot-hole-borer-html/">infested wood from being moved</a> from one area to another. Although researchers there have shown that <a href="https://apsjournals.apsnet.org/doi/10.1094/PDIS-10-17-1569-RE">chemical control</a> of the beetle and fungus on individual trees can protect them, this has not been applied widely, and is typically only used to protect high value individual trees. </p>
<p>The major challenge in South Africa is to connect different stakeholders and government bodies through effective communication. Roles and responsibilities (also financial) of all contingents, at national, regional and local levels, should be clearly defined to avoid a duplication of efforts, and to ensure appropriate management strategies are devolved to regional and local government. </p>
<p>Structures are in place at the national level to deal with pests like these. Most pest invasions affect agricultural or forestry crops, and the Department of Agriculture, Fisheries and Forestry then engages with relevant stakeholders with strategic guidelines for control. For its part, the Department of Environmental Affairs is responsible for protecting the country’s natural forests and ecosystems. But it’s focus is usually on things like climate change, pollution and alien invasive weeds or animals. </p>
<p>At the local level municipalities has never had to deal with a problem like this, are not equipped to deal with it, and need clear and practical guidance from the national departments.</p>
<p>A consolidated strategy and pragmatic action plan is urgently needed. Pest risk assessments and countrywide surveys need to be done for the different sectors. We can learn a lot from <a href="http://eskalenlab.ucr.edu/pshb.html">ongoing research efforts</a> in California, but local research is needed to determine the impact of the pest on different tree hosts, especially native trees, and to evaluate possible control measures in different South African climatic regions. </p>
<p>Research results need to be translated in management strategies that can be rolled out to stakeholders like farmers, commercial foresters, nurseries, arborists, municipalities, and quarantine authorities. This implies that people need to be trained to recognise the problem in order to appropriately deal with it. </p>
<p>Special policy might need to be formulated by the different levels of government, but legislation is only as good as its enforcement. For any of the above to succeed, efficient communication channels and a public awareness campaign is needed. All of this needs leadership, dedicated and competent human resources, and funds.</p>
<p>One thing is sure, the little shothole borer is here to stay. Protecting the country’s trees is everybody’s responsibility, but our government needs to lead the way.</p><img src="https://counter.theconversation.com/content/102996/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wilhelm de Beer receives funding from the National Research Foundation, the Tree Protection Co-operative Progamme, and the University of Pretoria. </span></em></p><p class="fine-print"><em><span>Trudy Paap receives funding from the South African National Biodiversity Institute and the Tree Protection Cooperative Programme</span></em></p>A tree-killing beetle has invaded South Africa. This is what should be done.Wilhelm de Beer, Associate Professor, University of PretoriaTrudy Paap, Postdoctoral Fellow Forestry and Agricultural Biotechnology Institute, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/920502018-02-27T15:21:43Z2018-02-27T15:21:43ZA tiny beetle and its deadly fungus is threatening South Africa’s trees<figure><img src="https://images.theconversation.com/files/207838/original/file-20180226-140217-1wdnfwt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The polyphagous shothole borer is tiny - but a fungus it's commonly associated with can be deadly for trees.</span> <span class="attribution"><span class="source">Wilhelm de Beer</span></span></figcaption></figure><p>Sandton is Johannesburg’s economic hub – home to numerous companies’ headquarters and the Johannesburg Stock Exchange. And now it has a new, unwelcome resident: a tiny beetle that could lay waste to several tree species found in the suburb and potentially the wider Johannesburg area. This is particularly concerning, as Johannesburg is considered one of the world’s largest urban forests, with <a href="http://www.jhbcityparks.com/index.php/street-trees-contents-29">more than 10 million trees</a>. </p>
<p>The polyphagous shothole borer, or <em>Euwallacea fornicatus</em>, seems to be a newcomer to South Africa. It was discovered in the country <a href="https://www.fabinet.up.ac.za/index.php/research/7">for the first time in 2017</a> by <a href="https://www.fabinet.up.ac.za/index.php/people-profile?profile=1230">Dr Trudy Paap</a>, a postdoctoral fellow at a <a href="https://www.fabinet.up.ac.za/">biotechnology institute</a> at the University of Pretoria. </p>
<p>During a survey for diseases in the KwaZulu-Natal Botanical Gardens in Pietermaritzburg, Paap found a lane of infested plane trees. The identity of the beetle was subsequently confirmed and the tiny beetle – they are each about 2mm long – has been found at work in gardens and roadsides in Johannesburg, about 500 km from Pietermaritzburg. </p>
<p>The beetle isn’t alone. It carries several fungal species with it when it infests living trees. One of these, <em>Fusarium euwallacea</em>, seems to be a permanent associate of the beetle. This fungus can eventually kill a beetle-infested tree. </p>
<p>The beetle and the fungus have devastated trees in California in the US as well as in Israel. Insecticides aren’t effective because the beetles bore deep into the wood. The only known method of managing the spread is to cut down infested trees and burn them. But research is underway to find more effective methods.</p>
<h2>A threat to native forests and fruit trees</h2>
<p>In late January my colleagues and I at the Forestry and Agricultural Biotechnology Institute were contacted by Niel Hill, an urban forestry consultant in Johannesburg. He was concerned about several dying trees in the Sandton area. Symptoms varied on different tree species from patches of white powdered wood (called <a href="https://www.amentsoc.org/insects/glossary/terms/frass">frass</a>), to blotches of oozing resin, on the bark surrounding the beetles’ entrance holes. On some trees he had also spotted small, elevated lesions on the bark resembling shotgun wounds. </p>
<p>Hill said that trees had already started dying with these symptoms in 2015, but the cause was unknown. Microscopic and DNA tests in the the institute’s laboratories confirmed that the polyphagous shothole borer and its fungus had arrived in Sandton.</p>
<p>The tree species affected in the Sandton area include non-native ornamental trees such as Japanese and Chinese maple, London plane, kapok, and liquid amber. Several paper bark trees, native to South Africa, were also heavily infested and dying. </p>
<p>The polyphagous shothole borer doesn’t appear to have done much damage to trees in <a href="http://onlinelibrary.wiley.com/doi/10.1111/afe.12215/full">Southeast Asia, its place of origin</a>. That’s probably because tree species evolved with the beetle and the fungus and have developed resistance towards them. It might also be because there are natural enemies controlling populations of the beetle in its native habitat. </p>
<p>But it’s a different story in <a href="https://doi.org/10.1094/PDIS-03-12-0276-PDN">California</a> in the US and in <a href="https://link.springer.com/article/10.1007%2Fs12600-012-0223-7">Israel</a>. The beetle and its fungus were introduced in these countries during the past 15 years and have caused serious damage, especially on avocado trees. </p>
<p>Paap’s work has confirmed that the South African beetle and fungus are the same genotypes as those found in Israel and California.</p>
<h2>An extremely wide range of host tree species</h2>
<p>Astonishingly, <a href="https://apsjournals.apsnet.org/doi/10.1094/PDIS-11-12-1026-RE">surveys</a> in two botanical gardens in Los Angeles have shown that the beetle-fungus complex can infest more than 200 tree species from 58 plant families. This is quite unusual; forest pests usually affect trees of the same genus or family. </p>
<p>The <a href="https://apsjournals.apsnet.org/doi/10.1094/PDIS-11-12-1026-RE">lists of infested trees from California</a> include important crop trees like avocado, macadamia, pecan, peach, orange and grapevine. Some of the susceptible trees are South African species that have been planted in the Los Angeles botanical gardens . These included the cabbage tree, common calpurnia, monkey plum, dwarf and common coral trees, and the honey flower, also sometimes called kruidjie-roer-my-nie.</p>
<p>The fact that native South African tree species are susceptible is particularly worrying. Although the California study provided some clues about the range of tree species susceptible, scientists simply don’t know and cannot predict what the beetle and fungus will do in South Africa – on crops like avocado or on native trees. </p>
<p>This has prompted the institute to start several research projects that range from developing fast DNA-based diagnostic tools for the fungus and beetle, to possible control measures. </p>
<p>During the past week scientists and government officials, representing the Department of Agriculture, Forestry and Fisheries and the Johannesburg City Parks and Zoo met with our team to discuss next steps. A <a href="https://www.fabinet.up.ac.za/index.php/news-item?id=639">working group</a> has been set up to co-ordinate monitoring the spread of the beetle and managing research efforts. It will also advise government agencies, municipalities, industry and private tree growers.</p>
<h2>Next steps</h2>
<p>The public can help, too. We’ve made an appeal to gardeners to watch out for the beetles. Details including photographs of the symptoms, GPS coordinates or a street address, the host tree species and the reporter’s contact details can be sent to diagnostic.clinic@fabi.up.ac.za.</p>
<p>We’re also appealing to people not to spread the problem by moving plant material with signs of beetle infestation. Instead, infested branches should be cut into small pieces and put into refuse bags, sealed and kept in direct sunlight. The heat from the sun will kill the insect and its larvae. Alternatively, wood should be burnt on site.</p><img src="https://counter.theconversation.com/content/92050/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wilhelm de Beer receives funding from National Research Foundation, Tree Protection Co-operative Programme, and the DST-NRF Centre Of Excellence In Tree Health Biotechnology. </span></em></p>The beetle and the fungus have devastated trees in California in the US as well as in Israel. Now they’re in South Africa.Wilhelm de Beer, Associate Professor, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/900262018-01-29T17:26:43Z2018-01-29T17:26:43ZProtecting cassava from disease? There’s an app for that<figure><img src="https://images.theconversation.com/files/201754/original/file-20180112-101492-3xpuf8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Cassava leaves at a market in the Democratic Republic of Congo.</span> <span class="attribution"><span class="source">Reuters/James Akena</span></span></figcaption></figure><p><a href="https://plantvillage.org/topics/cassava-manioc/infos">Cassava</a> is one of the developing world’s most important crops. Its starchy roots and leaves are a staple food for more than 500 million people in Africa each day. And Africa produces half of the world’s total cassava output; the continent’s main growers are the Congo, Côte d'lvoire, Ghana, Nigeria, Tanzania and Uganda.</p>
<p>It’s also climate resilient, as it is predicted to <a href="https://link.springer.com/article/10.1007%2Fs12042-012-9096-7">improve yield</a> in higher temperatures. Its role as a staple food will become ever more important, then, as climate change continues to take hold. </p>
<p>But cassava, like many other crops, is vulnerable to viruses and other plant diseases. These diseases can affect cassava yields, cost farmers money, and threaten food security in sub-Saharan Africa. Two diseases, cassava mosaic disease and cassava brown streak disease, have become the largest constraints to cassava production and food security in sub-Saharan Africa resulting in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5663696/">losses of over US$1 billion</a> every year.</p>
<p>These plant diseases are not new to Africa and have been causing losses for many decades. However, a lack of infrastructure and engagement by trained plant disease experts with farmers means the farmers are not trained to recognise them in their early stages. That’s why we set out to create a disease-recognition app for smartphones. We tested the ability of an image recognition model, called a convolutional neural network, to accurately identify up to five different cassava diseases. </p>
<p>The model is deployed using a mobile device’s camera. What’s novel about it is that it can run entirely on a smartphone without the need for a wireless connection, or access to large processing power. Once farmers have identified the disease using the app, we provide the necessary information so they can go ahead and treat their plants.</p>
<p><a href="https://www.frontiersin.org/articles/10.3389/fpls.2017.01852/full">Our results</a>, based on research conducted in Tanzania, show that the image recognition model had up to 98% accuracy in identifying cassava diseases in the field. </p>
<p>These results are promising as our method is much simpler to implement than traditional computer vision models. The model was also trained on a desktop with vastly smaller computing power than the typical supercomputer used in training image recognition models. These results highlight our method’s potential to be a reliable, fast, affordable and easily deployable strategy for digital plant disease detection. </p>
<p>We were also able to deploy the model on a smartphone without an Internet connection, something no other mobile app for plant disease diagnosis has been able to do. For the continent of Africa where data costs are high for smallholder farmers the ability to provide a diagnosis offline is critical. </p>
<h2>Creating a dataset</h2>
<p>Traditional disease identification approaches rely on the support of agricultural experts visiting a field and checking on crops. But these approaches are limited in countries with low logistical and human infrastructure capacity, and are expensive to scale up. </p>
<p>In such areas, smartphones offer new tools for in-field plant disease detection based on automated image recognition that can aid in large scale early detection. This is a viable tool for Africa: smartphone adoption is <a href="https://www.gsmaintelligence.com/research/?file=3bc21ea879a5b217b64d62fa24c55bdf&download">growing rapidly</a> on the continent. </p>
<p>Our technique is suitable for providing help to smallholder farmers, for several reasons. Firstly, it is fast: a disease can be identified with the model in less than one second. Because the app is on a mobile device, it is also easily deployed over large areas – farmers no longer need to wait for an agricultural expert to visit them and check their plants </p>
<p>We put the model, which works on Android phones, to the test in collaboration with research staff at the <a href="http://www.iita.org/">International Institute for Tropical Agriculture</a> in Dar es Salaam, Tanzania. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/479p-PEubZk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Putting the app to work in the field.</span></figcaption>
</figure>
<p>There were six class labels for the model: three disease classes, two mite damage classes and one healthy class (that is, a lack of disease or mite damage on the leaf.) </p>
<p>We then trained our model to identify the three diseases and two types of pest damage, or lack thereof. After training the model and loading it on to a phone app, researchers went out to test the app in the field. Staff from the institute would walk around fields holding the phone up to different cassava plants to see how the app responds. If no disease is recognised the app says the leaf is healthy. </p>
<p>The model was able to identify diseases, pest damage and healthy plants with a high degree of accuracy – up to 98% in some classes.</p>
<p>This particular model is now being used by researchers at the institute. Planned steps in 2018 include designing the app to make it suitable for farmers in East Africa, especially female farmers. For example, the app is currently being designed in English and Swahili, with both text and voice features. Our app is linked to <a href="http://plantvillage.psu.edu">PlantVillage</a> which is the largest source of free knowledge on crop health in the world. </p>
<h2>Huge chance for change</h2>
<p>This kind of technology can be transformative for smallholder farmers, who <a href="https://www.globalagriculture.org/fileadmin/files/weltagrarbericht/IAASTDBerichte/SubglobalReportSubSaharanAfrica.pdf">produce 70%</a> of Africa’s food supply. With access to information about diseases in their fields, this tool is an efficient extension system that can reach smallholder farmers with targeted diagnoses and advice.</p><img src="https://counter.theconversation.com/content/90026/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Technology is changing how plant diseases are recognised and dealt with by small scale farmers in Africa.Amanda Ramcharan, Postdoctoral Researcher, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/840242017-11-26T23:46:19Z2017-11-26T23:46:19ZStudying circadian rhythms in plants and their pathogens might lead to precision medicine for people<figure><img src="https://images.theconversation.com/files/195885/original/file-20171122-6020-15wox5s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Though not this obvious from the outside, plants are keeping time.</span> <span class="attribution"><span class="source">Hua Lu</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>At dusk, the leaves of the tamarind tree close, waiting for another dawn. Androsthenes, a ship captain serving under Alexander the Great, made the first written account of these leaf movements in the fourth century B.C.</p>
<p>It took centuries longer to discover that he was describing the effects of the circadian clock. This internal time-sensing mechanism allows many living organisms to keep track of time and coordinate their behaviors along 24-hour cycles. It follows the regular day/night and seasonal cycles of Earth’s daily rotation. Circadian research has advanced so far that the <a href="https://www.nobelprize.org/nobel_prizes/medicine/laureates/2017/">2017 Nobel Prize</a> in physiology or medicine was awarded for the groundbreaking work that <a href="https://theconversation.com/nobel-winners-identified-molecular-cogs-in-the-biological-clocks-that-control-our-circadian-rhythms-85061">elucidated the molecular basis underlying circadian rhythms</a>.</p>
<p>Biologists like us are studying the circadian clocks in plants for insights into how they affect the health and well-being of all life on Earth. As researchers continue to untangle more about how these clocks work – including how they influence interactions between hosts and their invading pathogens and pests – new forms of specially timed precision medicine could be on the horizon.</p>
<h2>Our hidden pacemaker</h2>
<p>Organisms from all three domains of life possess an amazing diversity of circadian rhythms. Seemingly simple <em>Cyanobacteria</em> <a href="https://doi.org/10.1038/nrmicro.2016.196">alternate photosynthetic activity between day and night</a>. The fungus <em>Neurospora crassa</em> produces <a href="https://www.ncbi.nlm.nih.gov/pubmed/21707668">spores every morning just before dawn</a>. Migratory monarch butterflies use a delicate <a href="https://doi.org/10.1016/j.celrep.2016.03.057">sun compass in their annual migration</a>. Almost <a href="https://www.nigms.nih.gov/education/pages/Factsheet_CircadianRhythms.aspx">every aspect of human activity</a> is influenced by the circadian clock – you can easily see this in yourself if you fly across time zones or engage in shift work.</p>
<p>The driving force behind circadian rhythms is what scientists call the <a href="https://doi.org/10.1038/nsmb.3327">circadian clock’s central oscillator</a>, an elaborate network of genes that turn each other’s activity on and off. Together, they form complex feedback loops that accurately calibrate time.</p>
<p>Although individual clock genes are not always the same across domains of life, the feedback mechanism of the central oscillator is. This mechanism acts as a switch to synchronize an organism’s daily activities with day and night fluctuations and other environmental changes. Such amazing balancing acts reflect organisms’ abilities to anticipate changing environment throughout the day. </p>
<h2>Precise timekeeping and health</h2>
<p>A well-calibrated circadian clock is critical for growth and fitness, which is why misalignment of the circadian clock with environmental cues causes diverse and far-reaching health issues. Some human diseases, including <a href="https://doi.org/10.1126/scitranslmed.3003200">diabetes</a>, <a href="https://doi.org/10.1073/pnas.1008734107">obesity</a>, <a href="https://doi.org/10.1515/hmbci-2013-0057">cardiovascular disease</a> and <a href="https://doi.org/10.1007/s11920-014-0483-7">some psychiatric disorders</a> such as depression and bipolar disorder, are likely linked to circadian clocks being out of sync with the environment. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=236&fit=crop&dpr=1 600w, https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=236&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=236&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=297&fit=crop&dpr=1 754w, https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=297&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/195917/original/file-20171122-6016-ewil30.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=297&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">After infection by a fungus, plants with a mutant circadian clock (right) showed much more damage than the normal plants (left).</span>
<span class="attribution"><span class="source">Hua Lu</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Increasing evidence also links the circadian clock to plant health. In particular, plant scientists have shown that a properly tuned <a href="https://doi.org/10.1146/annurev-phyto-080516-035451">circadian clock is important for plant disease resistance</a> to arrays of pathogens and pests. Although plants do not produce antibodies or use specialized immune cells to ward off invaders, some aspects of their immune system are similar to ours. Because of how easy it is to grow and genetically manipulate them, some plants, like <em>Arabidopsis</em>, serve as ideal systems to investigate how the circadian clock influences the outcome of diseases in plants once infected.</p>
<h2>Plant-pathogen interactions around the clock</h2>
<p>Plants, being immobile, must strategically allocate their limited energy and resources when faced with pathogens and pests. They have the sophisticated ability to <a href="https://doi.org/10.1146/annurev-phyto-080516-035451">time their defense</a>, which allows them to anticipate likely attacks before they occur and modulate defense responses to real attackers.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=323&fit=crop&dpr=1 600w, https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=323&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=323&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=405&fit=crop&dpr=1 754w, https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=405&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/196307/original/file-20171124-21838-1fowi5t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=405&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Stomata are little pores on the plant’s surface that can open and close.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-vector/opening-closing-stomata-411951568">Valentina Moraru/Shutterstock.com</a></span>
</figcaption>
</figure>
<p>The forefront of plant defense is on the surface. Physical features like trichomes, little hairs that stick out, protectively cover a plant, and wax coatings deter invaders from clinging onto the surface. The plant surface also has numerous mouth-like pores called stomata. Normally, <a href="https://doi.org/10.1038/nrg3976">stomata rhythmically open in the day and close at night</a>, a process regulated by the circadian clock in anticipation of light and humidity changes. While this process is important for photosynthesis and water exchange, opening stomata can be used by some pathogens as portals to access nutrients and space inside the plant tissue and closing stomata restrict pathogen invasion. </p>
<p>Beyond frontline physical barriers, plants have evolved complex surveillance systems to detect pathogens and pests as intruders. When cell surface receptors recognize a pathogen, the plant immediately closes its stomata at the invasion site. <a href="https://doi.org/10.1371/journal.ppat.1003370">Dysfunctional circadian clocks impair stomatal closure</a>, resulting in more severe disease.</p>
<p>Further pathogen recognition sends alert signals deep into the plant tissue, activating an arsenal of defense responses, including reprogramming of gene expression, production of antimicrobial compounds and enhancement of defense signaling. Even in the absence of pathogens, many of these responses show low but rhythmic changes that are influenced by the circadian clock. When a real attack arrives, the plants’ daily rehearsal of their defense systems ensures a <a href="https://doi.org/10.1146/annurev-phyto-080516-035451">strong and concerted timely defense</a>. Plants with misaligned clocks succumb to the attack. </p>
<p>One excellent example of a plant timing its defense comes from <a href="https://sites.duke.edu/donglab/">Xinnian Dong’s group</a> at Duke University. <em>Hyaloperonospora arabidopsidis</em> is a pathogen that disseminates its virulent spores in the morning and causes disease in <em>Arabidopsis</em> plants. Dong’s group elegantly showed that <em>Arabidopsis</em> anticipates this attack by expressing a set of defense genes at dawn that gives resistance against the pathogen. When the researchers disrupted the <em>Arabidopsis</em> circadian clock, it abolished this <a href="https://doi.org/10.1038/nature09766">morning defense</a> and made the plant more susceptible. </p>
<p>Plants also rely on timely defense to fight off insects. For instance, cabbage loopers have peak feeding activity before dusk. Beautiful work by <a href="http://www.bioc.rice.edu/%7Ebraam/">Janet Braam’s group</a> at Rice University showed that <em>Arabidopsis</em> produces the defense signaling hormone jasmonic acid with a peak at noon in anticipation of this attack. When the insects actually strike, the circadian clock <a href="https://doi.org/10.1073/pnas.1116368109">boosts this noon defense</a>, producing more jasmonic acid to inhibit insect feeding. </p>
<h2>Do clocks dance in pairs?</h2>
<p>As seen from these examples, pathogens and pests have their own circadian clocks and use them to determine the best time to be active. How does this ability affect their invasions of hosts? So far, researchers aren’t sure whether pathogen and pest clocks are coordinated to that of the host. If they are, then how in sync they are could determine the outcome of their interactions.</p>
<p>Current evidence indicates that some eukaryotic microbes, such as <a href="https://doi.org/10.1038/nature09766"><em>Hyaloperonospora arabidopsidis</em></a> and <a href="https://doi.org/10.1105/tpc.112.102046"><em>Botrytis cinerea</em></a>, are able to manipulate the <em>Arabidopsis</em> circadian clock. Even prokaryotic pathogens, like <a href="https://doi.org/10.1371/journal.ppat.1003370"><em>Pseudomonas syringae</em></a>, in spite of lacking a canonical central oscillator, can interfere with plant clocks in various ways.</p>
<p>In humans and mice, <a href="https://doi.org/10.1016/j.cell.2014.09.048">some populations of gut microbiota oscillate daily</a>, depending on the host circadian clock. Interestingly, <a href="https://doi.org/10.1177/0748730417729066">gut microbiota are capable of reprogramming the host clock</a>. How does this transkingdom communication occur? How can it influence the outcome of host and microbe interactions? Research in this area represents a fascinating and unexplored level of host-invader dynamics.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/196308/original/file-20171124-21801-qcc5qi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Well-timed actions in plants – like the tamarind tree’s closing leaves noticed by Androsthenes millennia ago – could eventually help us design more precise medicines.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-tamarind-leaves-blur-background-481065826">oraphan_nan/Shutterstock.com</a></span>
</figcaption>
</figure>
<h2>The clock as healer and helper</h2>
<p>The ability to integrate time cues with development and responses to environmental assaults is an evolutionary adaptation. Plants have taught biologists much about circadian rhythms and their role in modulating everything from development to defense.</p>
<p>Clock research has opened an opportunity to apply this knowledge to other systems, including humans. How can we modify the daily cycling of certain defense features to enhance immunity without causing developmental stress? What times of day are we most susceptible to certain pathogens? What are the most invasive times of day for various pathogens and pests?</p>
<p>Answers to questions like these will help unravel host-pathogen/pest interactions, not just in plants but also in people. Ultimately, this knowledge could contribute to the design of precision medicines that are tailored to boost timely defense in individual people to fight against various pathogens and pests. In addition, our understanding of plant disease resistance will aid agricultural control of pathogens and pests, mitigating the global challenge of crop loss.</p>
<p>Ongoing research continues to reveal how the influence of circadian rhythms extends as boundlessly as the sun’s rays.</p><img src="https://counter.theconversation.com/content/84024/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hua Lu receives funding from National Science Foundation. </span></em></p><p class="fine-print"><em><span>Linda Wiratan receives funding from the UMBC Undergraduate Research Award.</span></em></p>Precisely calibrated timekeepers are found in organisms from all domains of life. Biologists are studying how they influence plant/pathogen interactions – what they learn could lead to human medicines.Hua Lu, Associate Professor of Biological Sciences, University of Maryland, Baltimore CountyLinda Wiratan, B.S. Student of Biochemistry and Molecular Biology, University of Maryland, Baltimore CountyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/737102017-04-10T13:19:13Z2017-04-10T13:19:13Z“Pathogen hunters”: citizen scientists track plant diseases to save species<figure><img src="https://images.theconversation.com/files/163445/original/image-20170331-31760-1tpk734.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Author Joey Hulbert explaining sampling protocol.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>Plant diseases threaten <a href="http://www.nature.com/nature/journal/v484/n7393/full/nature10947.html">food security</a> and <a href="https://pdfs.semanticscholar.org/cbfe/71975cc7736a392f1feba0e71e19f9b8f756.pdf">sustainability</a>. They affect ecosystems and <a href="http://onlinelibrary.wiley.com/doi/10.1890/070151/full">change natural environments</a>. They cost money, too. An enormous amount is spent globally each year to control these diseases; the damage they cause is also hugely expensive. For example, crop losses from plant killing microbes are estimated to have cost the US $33 billion per year according to a <a href="https://www.forestpests.org/pdf/Update%20on%20the%20environmental%20and%20economic%20costs%20associated%20with%20alien-invasive%20species%20in%20the%20US.pdf">2005 report</a>. </p>
<p>New plant disease epidemics are emerging all the time. <a href="http://www.ingentaconnect.com/content/ima/imafung/2013/00000004/00000001/art00024">Myrtle rust</a> is an example of a disease recently identified in South Africa. It now threatens natural areas containing Myrtaceous plants and is of concern for many forestry industries growing Australian <em>Eucalyptus</em> species. </p>
<p>The emergence of new plant disease epidemics is largely driven by <a href="http://www.alachuacounty.us/Depts/epd/EPAC/AAAS%20Forest%20health%20and%20global%20change%20-%20Science-2015-Trumbore-814-8.pdf">globalisation</a>. Humans are the major pathway of spreading microbes that cause plant disease. But people are generally unaware of the risk and potential of their movement since the microbes in question are microscopic. We can’t see them, so we don’t think much about them.</p>
<p>The effect of plant disease could be reduced if people are made more aware of the many pathways for plant-killing microbes – and why preventing their spread matters to us all. </p>
<p>That’s where citizen science projects, such as <a href="http://citsci.co.za">Cape Citizen Science</a>, can help. Citizen science projects are opportunities to release our inner scientist to expand scientific literacy and knowledge. Cape Citizen Science believes that everyone has a little bit of scientist in them.</p>
<h2>Plant-destroying microbes</h2>
<p>Researchers involved in the project invited the public to join up as “pathogen hunters” to find a group of plant-destroying microbes known as <a href="http://citsci.co.za/content/plant-destroyers"><em>Phytophthora</em></a> which was responsible for one of the worst plant disease epidemics known to humanity, the <a href="http://www.bbc.co.uk/history/british/victorians/famine_01.shtml">Irish potato famine</a>. The responsible organism, <a href="http://www.nature.com/nature/journal/v461/n7262/abs/nature08358.html"><em>Phytophthora infestans</em></a>, starved nearly a quarter of Ireland’s population and drove another quarter out of the country in the mid 1800s.</p>
<p><em>Phytophthora</em> species are also well known around the world for the diseases they cause in natural forests. Through epidemics such as <a href="http://www.suddenoakdeath.org/">Sudden Oak Death</a> in the US and <a href="https://www.dwg.org.au/what-is-phytophthora-dieback">Jarrah (Phytophthora) dieback</a> in Australia, they are <a href="http://forestphytophthoras.org/sites/default/files/educational_materials/dieback_report.pdf">known</a> for eliminating susceptible species from the environment. </p>
<p>Cape Citizen Science facilitates research about <em>Phytophthora</em> species in South Africa’s <a href="http://www.worldwildlife.org/ecoregions/at1202">Cape floristic region</a> in the extreme south western tip of Africa. Many species of plants are threatened in this biodiversity hotspot, which is often recognised as the <a href="http://www.capenature.co.za/care-for-nature/biodiversity/cape-floristic-region/">“hottest hotspot”</a> because of the exceptional degree of endemism, housing thousands of species that don’t naturally occur anywhere else on the planet. But little is known about the impact of <em>Phytophthora</em> on Cape Flora. The project aims to create a baseline of data about <em>Phytophthora</em> species diversity and distribution.</p>
<p>It’s important to survey the diversity of <em>Phytophthora</em> species in this region because there may be many that have never been discovered. There may also be many species that are known to science but have never been discovered in South Africa. And finally, it’s important to survey these organisms in a bid to detect a newly arrived species before it causes too much damage. </p>
<h2>Citizen scientist contributions</h2>
<p>Nearly 200 people have been involved as citizen scientists since the project launched in 2016. They contribute by reporting dying plants and submitting samples. Many reports and samples have come from areas that the researchers would not have found. </p>
<p>Citizens report dying plants using the online tool <a href="http://ispotnature.org">Ispot Nature</a>. Many observations have been added to the <a href="http://www.ispotnature.org/projects/dying-plants-in-the-fynbos-south-africa">Cape Citizen Science project</a> and, again, include several that would not have been found by the scientists alone.</p>
<p>Ordinary people can also get involved by <a href="http://citsci.co.za/submit">submitting samples</a> of dying plants, soil, and even collections of microbes growing on petri-plates provided by the project. Samples have been submitted from home gardens, plant productions and recreational activities. </p>
<p>The project also offers workshops so citizens can learn to recognise and sample plant disease. Each workshop starts with a presentation about the research, incorporates a hike to find sick plants and ends with an activity to isolate and culture the microscopic organisms. </p>
<p>This format is also the basis for educational activities organised with children. The project has involved youth such as the <a href="http://www.eco-rangers.co.za/">Helderberg Eco-rangers</a> and is currently organising activities with the <a href="http://saep.org">South African Education and Environment Project</a> and <a href="http://visionafrika.com/">Vision Afrika</a>. These activities are a way to inspire the next generation of naturalists and scientists.</p>
<p>Citizen science projects have exceptional merit for the early detection of new plant disease epidemics. By incorporating many observers, more observations are made across space and time – and at a relatively low cost. And citizen science works: the Myrtle rust pathogen in South Africa was first discovered through a citizen’s report.</p>
<h2>Opportunities for growth</h2>
<p>Cape Citizen Science is an example of a grassroots project that has built a community of citizen scientists. It’s supported by the <a href="http://www.fabinet.up.ac.za/research-groups/dst-nrf-centre-of-excellence-in-tree-health-biotechnology">DST-NRF Centre of Excellence in Tree Health Biotechnology</a>, the <a href="http://www.fabinet.up.ac.za/">Forestry and Agricultural Biotechnology Institute</a>, <a href="http://www.up.ac.za/">University of Pretoria</a>, and <a href="http://www.sun.ac.za/Home.aspx">Stellenbosch University</a>.</p>
<p>Although our work is regional, the model could be implemented on a larger scale and in other countries. Hopefully this project will serve as an example and a learning platform to help other research areas and other countries establish their own projects to involve more citizens.</p><img src="https://counter.theconversation.com/content/73710/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joey Hulbert does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The impact of plant disease may be reduced if people are made aware of the many pathways for plant-killing microbes – and why preventing their spread matters to us all.Joey Hulbert, PhD Student, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/711122017-01-24T09:09:09Z2017-01-24T09:09:09ZHow GM crops can help us to feed a fast-growing world<figure><img src="https://images.theconversation.com/files/153298/original/image-20170118-26582-1mtximm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>The United Nations forecasts global population to rise to <a href="http://www.un.org/en/development/desa/news/population/2015-report.html">more than 9 billion people</a> by 2050. Climate change may mean that the crops we depend on now may <a href="http://www.nature.com/articles/nplants2016202">no longer be suited</a> to the areas where they are currently cultivated and may increasingly be threatened by <a href="https://www.scientificamerican.com/article/yes-some-extreme-weather-can-be-blamed-on-climate-change/?WT.mc_id=SA_TW_ENGYSUS_NEWS">droughts, floods</a> and the <a href="http://www.nature.com/nclimate/journal/v3/n11/full/nclimate1990.html">spread of plant diseases</a> due to altered weather patterns. So feeding everyone in the coming decades will be a challenge – can genetically modified crops help us achieve this? </p>
<p>Two groups of genetically modified crops are widely grown. The first are altered so that they are <a href="http://sitn.hms.harvard.edu/flash/2015/roundup-ready-crops/">not affected by the herbicide glyphosate</a>, which means that farmers can eliminate weeds without harming their crop. Glyphosate-resistant crops can increase farming efficiency but, while helping to get rid of weeds, herbicide resistance has no direct effect on the quantity of food produced, so their contribution to food security is likely to be limited. </p>
<p>The second type produce a natural insecticide <a href="http://sitn.hms.harvard.edu/flash/2015/insecticidal-plants/">inside the parts of the plant that pests eat</a>. This protects the yields of these crops against insect infestation, which is arguably more environmentally friendly than using sprays that could be toxic to other organisms. Crops of this type are likely to be useful, <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4908423/">but we should increase the number of insecticide genes</a> that we employ to prevent evolution of resistant pests. </p>
<p>Farmers have always faced crop diseases – think of the Irish potato famine of the 19th century – and some scientists predict that climate change may allow previously contained infections <a href="http://www.envirochange.eu/download/free_publications/EnviroChangeProject_Booklet2012_Pertot_Elad.pdf">to spread into new areas and become more damaging</a>. It may already have contributed to the <a href="https://www.csis.org/analysis/severe-climate-change-driven-wheat-fungus-found-bangladesh-highlighting-need-risk">devastating appearance of a fungal infection called wheat blast in Bangladesh</a>, a disease that can cause <a href="http://www.cimmyt.org/wheat-blast/">nearly complete loss of this critical crop in infected fields</a>.</p>
<h2>Disease resistance</h2>
<p>Genetic modification can certainly be used in the fight to make crops more disease resistant. Many plants are vulnerable to an infection because they cannot detect the invading organism. However, the proteins that identify an infection and activate a plant’s defences can be moved between <a href="http://www.pnas.org/content/100/16/9128.full.pdf">varieties</a> or even <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0042036">species</a> using genetic modification. This will enable previously vulnerable crops to turn on resistance mechanisms.</p>
<p>It is also becoming possible to rewrite the genes for these gatekeeper proteins so that they <a href="http://apsjournals.apsnet.org/doi/10.1094/MPMI-07-15-0147-R">work for different diseases</a>. A powerful and rapid method for <a href="https://www.neb.com/tools-and-resources/feature-articles/crispr-cas9-and-targeted-genome-editing-a-new-era-in-molecular-biology">editing genes called CRISPR-Cas9 has recently been developed</a> and it is already being harnessed to produce genetically modified crops. For example, genes that make wheat vulnerable to powdery mildew have been changed to <a href="http://www.nature.com/nbt/journal/v32/n9/full/nbt.2969.html">produce a resistant variety</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/153302/original/image-20170118-26548-u5hqdr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/153302/original/image-20170118-26548-u5hqdr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=409&fit=crop&dpr=1 600w, https://images.theconversation.com/files/153302/original/image-20170118-26548-u5hqdr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=409&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/153302/original/image-20170118-26548-u5hqdr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=409&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/153302/original/image-20170118-26548-u5hqdr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=513&fit=crop&dpr=1 754w, https://images.theconversation.com/files/153302/original/image-20170118-26548-u5hqdr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=513&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/153302/original/image-20170118-26548-u5hqdr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=513&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The CRISPR-Cas9 system for gene editing.</span>
<span class="attribution"><span class="source">ibreakstock</span></span>
</figcaption>
</figure>
<p>Nor is gene editing limited to improving disease resistance. Tomatoes have been tweaked to be insensitive to changes in the number of hours of sunlight in a day. This causes them to <a href="https://eurekalert.org/pub_releases/2016-12/cshl-gey_1120216.php">produce fruit more quickly</a> because they aren’t waiting for the right time of year to start flowering.</p>
<h2>Improving photosynthesis</h2>
<p>Fundamentally, agriculture uses photosynthesis to convert light energy, water and carbon dioxide into food – so <a href="http://onlinelibrary.wiley.com/doi/10.1111/nph.14307/full">improving this process</a> would increase how much food we produce. An obvious target is the step that captures carbon dioxide as it sometimes mistakes oxygen for carbon dioxide in a wasteful set of reactions called <a href="http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/066/Rubisco%20and%20C4%20plants.pdf?v=1353967268963">photorespiration</a>. </p>
<p>As it happens, some plants already have a solution to this problem. They possess a system that pumps carbon dioxide into <a href="http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/066/Rubisco%20and%20C4%20plants.pdf?v=1353967268963">specialised parts of the leaf where most photosynthesis occurs</a>, concentrating it there so that photorespiration doesn’t happen. These species, known as C4 plants, can make <a href="https://academic.oup.com/jxb/article-lookup/doi/10.1093/jxb/err179">more use of sunlight at higher temperatures</a> and <a href="http://rstb.royalsocietypublishing.org/content/367/1588/583.long">need less water</a> because the pores that let carbon dioxide into their leaves don’t have to open so much and therefore less water vapour escapes through them. </p>
<p>It has been estimated that transferring these mechanisms into other crop species such as rice could increase productivity by 50%. Unfortunately, progress towards this goal has been slow, partly because <a href="https://langdalelab.com/research-2/kranz-anatomy/">rice doesn’t have the same leaf structure as C4 plants</a>. A version of rice that can carry out a <a href="https://www.technologyreview.com/s/535011/supercharged-photosynthesis/">simple version of C4 photosynthesis</a> has recently been produced but it will take at least ten years to optimise it. </p>
<p>Less ambitious approaches may provide benefits more quickly, such as a <a href="https://www.newscientist.com/article/2111377-trials-planned-for-gm-superwheat-that-boosts-harvest-by-20/">new type of wheat</a> in which productivity has been increased by 15% to 20% by speeding up recycling of ribulose bisphosphate which is crucial for carbon dioxide capture.</p>
<h2>Improving nutrition</h2>
<p>Crops are not just being genetically modified to improve their quantity but also their nutritional quality. The most prominent of these is “<a href="http://www.goldenrice.org/Content3-Why/why.php">golden rice</a>”. Vitamin A deficiency causes 250,000 deaths per year and is common in populations whose diet is heavily dependent on rice. Golden rice is golden because it produces large quantities of yellow dietary carotenoids that our bodies can convert into vitamin A. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/153588/original/image-20170120-5260-16q8g7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/153588/original/image-20170120-5260-16q8g7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/153588/original/image-20170120-5260-16q8g7a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/153588/original/image-20170120-5260-16q8g7a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/153588/original/image-20170120-5260-16q8g7a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/153588/original/image-20170120-5260-16q8g7a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/153588/original/image-20170120-5260-16q8g7a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Golden rice is engineered to be rich in vitamin A.</span>
<span class="attribution"><span class="source">Jiang Hongyan</span></span>
</figcaption>
</figure>
<p>Other “biofortified” crops in development include <a href="http://www.pnas.org/content/107/41/17533.full">potatoes with more protein</a> and <a href="http://www.nature.com/articles/nplants2016191">cooking bananas with increased carotenoids and iron</a>.</p>
<p>Many people – and countries – are still sceptical about GM food. But people and animals have now been consuming GM crops for more than 20 years <a href="http://www.tandfonline.com/doi/full/10.3109/07388551.2013.823595">without apparent harm to their health</a>. On the other hand, there is no question that starvation kills and that food insecurity is a major global threat. There are challenging times ahead. Can we afford to close the door on these powerful ways to protect our food supply?</p>
<hr>
<p>_This article is part of a series by The Conversation on food security. <a href="https://theconversation.com/uk/topics/food-security-2017-35230">Read other articles here</a>.</p><img src="https://counter.theconversation.com/content/71112/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stuart Thompson has received funding from MAFF and the Nuffield Foundation. </span></em></p>Many people are suspicious of GM crops, but new techniques could massively increase food production.Stuart Thompson, Senior Lecturer in Plant Biochemistry, University of WestminsterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/642062016-10-24T01:59:53Z2016-10-24T01:59:53ZWith the familiar Cavendish banana in danger, can science help it survive?<figure><img src="https://images.theconversation.com/files/142716/original/image-20161021-1763-13xoceb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Facing down a future with no bananas.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/35652152@N07/28004881235">Chris Richmond</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span></figcaption></figure><p>The banana is the world’s most popular fruit crop, with <a href="http://www.fao.org/economic/worldbananaforum/statistics/en/">over 100 million metric tons produced annually</a> in over 130 <a href="http://www.fao.org/docrep/019/i3627e/i3627e.pdf">tropical and subtropical countries</a>. Edible bananas are the result of a genetic accident in nature that created the seedless fruit we enjoy today. </p>
<p>Virtually all the bananas sold across the Western world belong to the <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0007/251899/Banana-growing-guide-cavendish-bananas-1.pdf">so-called Cavendish subgroup</a> of the species and are <a href="http://doi.org/10.1093/aob/mcm191">genetically nearly identical</a>. These bananas are sterile and <a href="http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0006/251898/Banana-growing-guide-cavendish-bananas-Complete.pdf">dependent on propagation via cloning</a>, either by using suckers and cuttings taken from the underground stem or through modern tissue culture.</p>
<p>The familiar bright yellow Cavendish banana is ubiquitous in supermarkets and fruit bowls, but it is in imminent danger. The vast worldwide monoculture of genetically identical plants leaves the Cavendish <a href="http://dx.doi.org/10.1371/journal.ppat.1005197">intensely vulnerable to disease outbreaks</a>. </p>
<p>Fungal diseases severely devastated the banana industry once in history and it could soon happen again if we do not resolve the cause of these problems. Plant scientists, including us, are working out the genetics of wild banana varieties and banana pathogens as we try to prevent a Cavendish crash. </p>
<h2>The cautionary tale of ‘Big Mike’</h2>
<p>One of the most prominent examples of genetic vulnerability comes from the banana itself. Up until the 1960s, Gros Michel, or “Big Mike,” was the prime variety grown in commercial plantations. Big Mike was so popular with consumers in the West that the banana industry established ever larger monocultures of this variety. Thousands of hectares <a href="http://www.apsnet.org/publications/apsnetfeatures/Pages/PanamaDiseasePart1.aspx">of tropical forests</a> in Latin America were converted into <a href="http://www.penguinrandomhouse.com/books/299017/banana-by-dan-koeppel/9780452290082">vast Gros Michel plantations</a>.</p>
<p>But Big Mike’s popularity led to its doom, when a pandemic whipped through these plantations during the 1950s and ‘60’s. A fungal disease called Fusarium wilt or Panama disease nearly wiped out the Gros Michel and brought the global banana export industry to the <a href="http://www.agriculturedefensecoalition.org/sites/default/files/pdfs/3T_2000_Banana_Destructive_Panama_Disease_2000.pdf">brink of collapse</a>. A soilborne pathogen was to blame: The fungus <em>Fusarium oxysporum</em> f.sp. <em>cubense</em> (Foc) <a href="http://dx.doi.org/10.1094/PHYTO-04-15-0101-RVW">infected the plants’ root and vascular system</a>. Unable to transport water and nutrients, the plants wilted and died.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142717/original/image-20161021-1778-1ihcafz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A cross-section of a banana plant, infected with the fungus that causes Fusarium wilt.</span>
<span class="attribution"><span class="source">Gert Kema</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Fusarium wilt is <a href="http://www.promusa.org/Fusarium+wilt">very difficult to control</a> – it spreads easily in soil, water and infected planting material. Fungicide applications in soil or in the plant’s stem are as of yet ineffective. Moreover, the fungus can persist in the soil for several decades, thus prohibiting replanting of susceptible banana plants. </p>
<h2>Is history repeating itself?</h2>
<p>Cavendish bananas are resistant to those devastating Fusarium wilt Race 1 strains, so were able to replace the Gros Michel when it fell to the disease. Despite being less rich in taste and logistical challenges involved with merchandising this fruit to international markets at an acceptable quality, <a href="http://www.apsnet.org/publications/apsnetfeatures/Documents/2005/PanamaDisease2.pdf">Cavendish eventually replaced Gros Michel</a> in commercial banana plantations. The <a href="http://www.fao.org/fileadmin/templates/est/COMM_MARKETS_MONITORING/Bananas/Documents/Banana_Information_Note_2014-_rev.pdf">entire banana industry</a> was restructured, and to date, Cavendish accounts for <a href="http://www.fao.org/docrep/007/y5102e/y5102e04.htm">47 percent of the bananas grown worldwide</a> and <a href="http://www.newyorker.com/magazine/2011/01/10/we-have-no-bananas">99 percent of all bananas sold commercially for export</a> to developed countries. </p>
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<a href="https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142718/original/image-20161021-1763-1fza2aq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Bananas in Costa Rica affected by Black Sigatoka.</span>
<span class="attribution"><span class="source">Gert Kema</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>But the Cavendish unfortunately has its own weaknesses – most prominently susceptibility to <a href="http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS.2003.87.3.208">a disease called Black Sigatoka</a>. The fungus <em>Pseudocercospora fijiensis</em> attacks the plants’ leaves, causing cell death that affects photosynthesis and leads to a reduction in fruit production and quality. If Black Sigatoka is left uncontrolled, <a href="http://doi.org//10.1111/j.1364-3703.2010.00672.x">banana yields can decline</a> by <a href="http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/BlackSigatoka.aspx">35 to 50 percent</a>.</p>
<p>Cavendish growers currently manage Black Sigatoka through a combination of pruning infected leaves and <a href="http://doi.org/10.17660/ActaHortic.2009.828.16">applying fungicides</a>. Yearly, it can take 50 or more applications of chemicals to control the disease. Such heavy use of fungicides has negative impacts on the environment and the occupational health of the banana workers, and increases the costs of production. It also helps select for survival the strains of the fungus with <a href="http://www.frac.info/working-group/banana-group">higher levels of resistance to these chemicals</a>: As the resistant strains become more prevalent, the disease gets harder to control over time.</p>
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<a href="https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=278&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=278&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=278&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=350&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=350&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142816/original/image-20161024-15958-1gmv13y.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=350&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Aerial spraying of fungicides on a banana plantation.</span>
<span class="attribution"><span class="source">Gert Kema</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>To further aggravate the situation, Cavendish is also now under attack from <a href="http://dx.doi.org/10.1094/PHYTO-04-15-0101-RVW">a recently emerged strain of Fusarium oxysporum</a>, known as Tropical Race 4 (TR4). First identified in the early 1990s in Taiwan, Malaysia and Indonesia, TR4 has since spread to many Southeast Asian countries and <a href="http://dx.doi.org/10.1094/PDIS-12-14-1356-PDN">on into the Middle East</a> and <a href="http://dx.doi.org/10.1094/PDIS-09-13-0954-PDN">Africa</a>. If TR4 makes it to Latin America and the Caribbean region, the export banana industry in that part of the world could be in big trouble.</p>
<p>Cavendish varieties have shown <a href="http://dx.doi.org/10.1038/504195a">little if any resistance against TR4</a>. Growers are relying on temporary solutions – trying to <a href="http://www.promusa.org/Fusarium+wilt">prevent it</a> from entering new regions, using clean planting materials and limiting the transfer of potentially infected soil between farms.</p>
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<a href="https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/142714/original/image-20161021-1796-1on3qw6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cavendish banana trees in China infected with new fungal disease TR4.</span>
<span class="attribution"><span class="source">Andre Drenth, UQ</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Black Sigatoka and Panama disease both cause serious production losses and are difficult to control. With the right monitoring in place to rapidly intervene and halt their spread, the risks and damage imposed by these diseases can be considerably reduced, as has been <a href="http://www.musalit.org/seeMore.php?id=14394">recently shown in Australia</a>. But current practices don’t provide the durable solution that’s urgently needed.</p>
<h2>Getting started on banana genetic research</h2>
<p>If there’s a lesson to be learned from the sad history of Gros Michel, it’s that reliance on a large and genetically uniform monoculture is a risky strategy that is prone to failure. To reduce the vulnerability to diseases, we need more genetic diversity in our cultivated bananas. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/140963/original/image-20161008-21433-5f2wkn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Local banana varieties in southern China.</span>
<span class="attribution"><span class="source">Andre Drenth, UQ</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Over a thousand species of banana have been recorded in the wild. Although most do not have the desired agronomic characteristics – such as high yields of seedless, nonacidic fruits with long shelf life – that would make them a direct substitute for the Cavendish, they are an untapped genetic resource. Scientists could search within them for resistance genes and other desirable traits to use in engineering and breeding programs.</p>
<p>To date, though, there’s been little effort and insufficient funding for collecting, protecting, characterizing and <a href="http://dx.doi.org/10.17660/ActaHortic.2011.897.4">utilizing wild banana genetic material</a>. Consequently, while almost every other crop used for food production has been significantly improved through plant breeding over the last century, the banana industry has yet to benefit from genetics and plant breeding.</p>
<p>But we have started taking the first steps. We now know the <a href="http://dx.doi.org/10.1038/nature11241">genome sequences of the banana</a> and the fungi that <a href="http://dx.doi.org/10.1371/journal.pone.0095543">cause Fusarium wilt</a> and <a href="http://dx.doi.org/10.1371/journal.pgen.1005904">Sigatoka</a>. These studies helped illuminate some of the molecular mechanisms by which these fungal pathogens cause disease in the banana. That knowledge provides a basis for <a href="http://dx.doi.org/10.1371/journal.pgen.1005904">identifying disease-resistant genes</a> in wild and cultivated bananas.</p>
<p>Researchers <a href="http://dx.doi.org/10.1371/journal.pgen.1005876">now have the tools</a> to <a href="https://www.google.co.in/patents/WO2011005090A1?cl=en">identify resistance genes</a> in wild bananas <a href="http://dx.doi.org/10.1073/pnas.1002910107">or other plant species</a>. Then they can use classical plant breeding or genetic engineering to transfer those genes into desired cultivars. Scientists can also use these tools to further study the dynamics and evolution of banana pathogens in the field, and monitor changes in their resistance to fungicides.</p>
<p>Availability of the latest tools and detailed genome sequences, coupled with long-term visionary research in genetics, engineering and plant breeding, can help us keep abreast of the pathogens that are currently menacing the Cavendish banana. Ultimately we need to increase the pool of genetic diversity in cultivated bananas so we’re not dependent on single clones such as the Cavendish or the Gros Michel before it. Otherwise we remain at risk of history repeating itself.</p><img src="https://counter.theconversation.com/content/64206/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>André Drenth receives funding from Horticulture Innovation Australia </span></em></p><p class="fine-print"><em><span>Gert Kema is a senior scientist and professor of tropical phytopathology at Wageningen University and Research. He receives funding for his R&D program on banana, see <a href="http://www.panamadisease.org">www.panamadisease.org</a>. He also co-founded two companies dealing with banana and owns shares in Yellow Pallet, a company that produces transport pallets from banana fiber. </span></em></p><p class="fine-print"><em><span>Ioannis Stergiopoulos does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Every single Cavendish banana plant worldwide is genetically identical. This vast monoculture sets them up for disastrous disease outbreaks. But researchers have ideas on how to protect the crop.Ioannis Stergiopoulos, Assistant Professor of Plant Pathology, University of California, DavisAndré Drenth, Professor of Agriculture and Food Sciences, The University of QueenslandGert Kema, Special Professor of Phytopathology, Wageningen UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/589462016-05-19T13:11:29Z2016-05-19T13:11:29ZHow to predict the next plant disease epidemic<figure><img src="https://images.theconversation.com/files/123191/original/image-20160519-30723-1x0ujxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The fungus Marasmiellus inoderma attacks weakened banana plants.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/scotnelson/5681923838/">Scot Nelson</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Britain was once full of elm trees. But the introduction of a microscopic fungus in the 20th century changed all of that. Over the course of two epidemics, <a href="http://www.forestry.gov.uk/fr/beeh-9u2k3p">60m elms were lost</a>, landscapes were irreversible changed and ecosystems altered forever. </p>
<p>Since then, UK forests have faced an onslaught of new invasions. These include <em>Phytophthora ramorum</em>, a “fungus-like” organism which attacks a number of trees including larch and some species of oak, and <a href="https://theconversation.com/britains-ash-forests-face-extinction-but-a-tree-named-betty-could-save-them-57922">ash dieback</a>, a disease first discovered in the UK in 2012 which caused such alarm that the government convened <a href="http://www.bbc.co.uk/news/science-environment-20219649">Cobra</a>, an emergency response committee usually reserved for terrorist threats and other such national emergencies.</p>
<p>As international trade and travel continues to increase, more plants are being shipped around the world, and more pests and diseases are showing up in unexpected places. This is a global issue, affecting agricultural crops and natural environments everywhere.</p>
<p>Citrus industries in the US and Brazil have suffered from a spate of exotic diseases originating from South-East Asia; in Florida “citrus canker” arrived in 1995 and US$1 billion was spent trying to eradicate it. In 2005 the towel was thrown in on the eradication program and that same year a far more devastating disease, “<a href="http://www.npr.org/sections/thesalt/2015/11/27/457424528/how-long-can-floridas-citrus-industry-survive">citrus greening</a>”, arrived and subsequently spread throughout the state. </p>
<p>Bananas across the world are threatened by <a href="https://theconversation.com/disease-may-wipe-out-worlds-bananas-but-heres-how-we-might-just-save-them-54082">a strain of “Panama disease”</a>. Wheat has been hit by a new virulent form of <a href="http://www.fao.org/agriculture/crops/thematic-sitemap/theme/pests/wrdgp/en/">stem rust disease</a> that was first discovered in Uganda in 1999, and has since spread across Africa and the Middle East. </p>
<p>There are many more such examples but the latest threat to Europe may be the scariest yet: a bacteria known as <a href="http://www.telegraph.co.uk/gardening/problem-solving/plant-disease-explained-the-dangers-of-xylella-fastidiosa/"><em>Xylella fastidiosa</em></a>. It’s thought to have arrived accidentally on coffee plants from <a href="http://apsjournals.apsnet.org/doi/abs/10.1094/PD-89-0687B">Costa Rica</a>. Xylella is spread by sap-feeding insects such as spittlebugs and invades a plant’s water distribution system, preventing essential water and nutrients from being transported around the plant.</p>
<p>But here’s the really worrying part. Whereas many plant diseases are capable of infecting only a small number of host species, Xylella has a vast list of potential hosts plants, depending on the particular sub-species of the pathogen, such as oaks, citrus and olive trees. The EC’s emergency measures,
including the removal of olive trees and other hosts, have caused <a href="http://www.oliveoiltimes.com/olive-oil-making-and-milling/olive-tree-felling-starts-in-apulia-amid-protests/47326">public uproar and protests</a> in the affected areas.</p>
<h2>We need spatial data – and maps</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1067&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1067&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1067&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1340&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1340&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123194/original/image-20160519-30689-1m73dtu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1340&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An olive tree in southern Italy is decorated with an anti-felling banner.</span>
<span class="attribution"><span class="source">Stephen Parnell</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>There is some light among all this doom and gloom, however. Advances in our ability to collect data on plant diseases, and then map them out, offers up the potential to harness spatial mapping technologies and computer modelling against these invading threats. </p>
<p>Unlike other types of invasive species (think Japanese knotweed, say, or rats on remote islands), plant diseases are incredibly good at evading detection. These microscopic organisms can inhabit plants for weeks, months or even years before even the first signs of the visual symptoms we need to spot them.</p>
<p>To try and second guess where new epidemics might pop up, people are increasingly developing maps of disease risk. For example, the US Department of Agriculture combines a range of risk factors associated with different diseases. These can be meteorological drivers such as wind and rainfall, or socio-economic factors such as how connected residents in a particular community are to areas where a disease is already found. These maps can then be used to identify potential hotspots where surveillance efforts can be targeted and any new disease quickly stamped out.</p>
<p>As spittlebugs can carry Xylella and thus demonstrate a local tree must be infected, researchers in Italy have combined these “spy insects” and real-time data from smartphones in the field to try and <a href="http://www.fupress.net/index.php/pm/article/viewFile/15250/15850">detect the disease</a> even before the plants show any symptoms. </p>
<p>Similar smartphone tech has been adopted in the UK project “Opal”, for instance, which has a <a href="http://www.opalexplorenature.org/tree-health-app">tree health survey app</a> that enables members of the public to identify different diseases and <a href="https://treealert.forestry.gov.uk/">report them</a>. All this information and new opportunities to detect and map outbreaks provides vital instant data on how diseases are spreading.</p>
<h2>Plant disease map-reading</h2>
<p>Plants don’t tell anyone when they get sick, so we have to actively search for new cases which is hard work. Better targeting of surveillance programs is incredibly important to find new epidemics and remove them before they get out of control. Together with Rothamsted Research and the US Department of Agriculture, colleagues and I at Salford are using <a href="http://rspb.royalsocietypublishing.org/content/282/1814">spatial information on epidemics</a> to help inform smart surveillance strategies.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=847&fit=crop&dpr=1 600w, https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=847&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=847&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1064&fit=crop&dpr=1 754w, https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1064&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/123199/original/image-20160519-30579-15oviqj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1064&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An old risk map for ‘citrus greening’ disease in Florida.</span>
<span class="attribution"><span class="source">Parnell et al</span></span>
</figcaption>
</figure>
<p>Researchers at Cambridge University have also developed state of the art computer models of invading diseases such as ash dieback and <a href="http://www.pnas.org/content/113/20/5640.abstract">sudden oak death</a>. This sort of work can predict in real-time where epidemics will develop and spread, and quickly identify areas of high risk.</p>
<p>Plant disease epidemics represent a growing and important threat to agricultural economies, food security and natural environments. It’s clear that, with the world becoming a smaller place, opportunities for plant diseases to move around the globe are only going to increase. New ways of detecting and mapping plant disease are sorely needed from the scientific community to help combat these global emergencies.</p><img src="https://counter.theconversation.com/content/58946/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Parnell receives funding from the US Department of Agriculture </span></em></p>Scientists are using maps and data to identify which areas are most at risk.Stephen Parnell, Lecturer in Spatial Epidemiology, University of SalfordLicensed as Creative Commons – attribution, no derivatives.