tag:theconversation.com,2011:/fr/topics/crop-damage-35788/articlesCrop damage – The Conversation2022-12-15T16:04:33Ztag:theconversation.com,2011:article/1965312022-12-15T16:04:33Z2022-12-15T16:04:33ZFungal toxins are widespread in European wheat – threatening human health and the economy<figure><img src="https://images.theconversation.com/files/500999/original/file-20221214-1149-y34rfu.jpg?ixlib=rb-1.1.0&rect=15%2C0%2C3478%2C2309&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Harmful fungal toxins are a growing threat for European wheat.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/production-wheat-flour-535439188">Sergey Butin/Shutterstock</a></span></figcaption></figure><p>Wheat <a href="https://link.springer.com/article/10.1007/s12571-013-0263-y">provides</a> 19% of the calories and 21% of the protein consumed by humans globally. But a fungal disease called <a href="https://ahdb.org.uk/knowledge-library/fusarium-and-microdochium-in-cereals">fusarium head blight (FHB)</a>, which can infect wheat crops and contaminate the grain with toxins, is on the rise. </p>
<p>These so-called mycotoxins – which include deoxynivalenol, commonly called “vomitoxin” – are a <a href="https://www.mdpi.com/1420-3049/26/2/454">threat</a> to human and livestock health and can cause vomiting, intestinal damage, weakened immune system, hormone disruption and cancer. </p>
<p>To protect consumers, the EU commission set <a href="https://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:364:0005:0024:EN:PDF">legal limits</a> on vomitoxin levels in wheat produced for food. Grain deemed too contaminated for human consumption is often downgraded to animal feed. But downgrading comes at a cost to farmers and the economy because animal feed has a lower monetary value than food. </p>
<p>Governments and agribusinesses routinely monitor mycotoxin levels in the food and animal feed supply chains. Yet the scale of FHB mycotoxin contamination in European wheat supplies is understudied and its economic impact had previously not been quantified.</p>
<p>With colleagues from the universities of Bath and Exeter, we <a href="https://www.nature.com/articles/s43016-022-00655-z">analysed</a> the largest available mycotoxin datasets and found that FHB mycotoxins are widespread in wheat produced for food and animal feed across Europe. We also found that the threat of mycotoxins – particularly in the south of Europe – is increasing over time. </p>
<h2>European wheat contaminated</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A wheat spike in the palm of a hand showing discolouration." src="https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501003/original/file-20221214-4682-q7fm05.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">A wheat spike showing Fusarium Head Blight symptoms.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/typical-fusarium-head-blight-fbh-symptom-2140986197">Dan Gabriel Atanasie/Shutterstock</a></span>
</figcaption>
</figure>
<p>Vomitoxin was present in every European country studied, and overall it was found in half of all wheat samples destined for food. In the UK, vomitoxin was found in 70% of the food wheat produced between 2010 and 2019. </p>
<p>Almost all (95%) of the vomitoxin contamination recorded in European wheat was within legal limits. This confirms that current legislation and the monitoring of FHB mycotoxin levels in food effectively safeguard European consumers against acute poisoning.</p>
<p>Yet the widespread presence of vomitoxin in our food is concerning. It is not yet known how constant, low-level dietary exposure to mycotoxins can affect human health in the long term. This is compounded by the fact that one-quarter of the wheat contaminated with vomitoxin also contained other FHB mycotoxins, raising concerns of <a href="https://www.sciencedirect.com/science/article/pii/S0041010112007143?via%3Dihub">synergism</a>, where toxins interact with each other and cause greater harm than the sum of the individual toxins acting alone.</p>
<h2>Economic cost of fungal toxins</h2>
<p>We also estimated the cost of vomitoxin to the European economy.</p>
<p>Vomitoxin was recorded in concentrations above legal limits in 5% of the wheat produced for food in Europe. Between 2010 and 2019, this was equivalent to 75 million tonnes of wheat. If all of this affected wheat was diverted to animal feed, we calculated that the loss in value for wheat producers would be €3 billion (£2.6 billion) over the period studied. </p>
<p>However, the total economic cost of the FHB disease in Europe is likely to be far higher. Our calculation does not include the reduction in wheat yields as a result of the disease, contamination with other harmful but less routinely tested mycotoxins, or the costs of applying fungicide to prevent the growth of the fungal pathogen.</p>
<figure class="align-center ">
<img alt="A tractor spraying fungicide on a wheat field as it drives through the field." src="https://images.theconversation.com/files/501302/original/file-20221215-17-purmy2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/501302/original/file-20221215-17-purmy2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/501302/original/file-20221215-17-purmy2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/501302/original/file-20221215-17-purmy2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/501302/original/file-20221215-17-purmy2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/501302/original/file-20221215-17-purmy2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/501302/original/file-20221215-17-purmy2.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">A tractor spraying fungicide on a wheat field to prevent the growth of fungi.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/farmer-spraying-green-wheat-field-504107407">oticki/Shutterstock</a></span>
</figcaption>
</figure>
<h2>Increasing threat</h2>
<p>FHB is a disease that fluctuates annually. But we found that mycotoxin levels increased in lower latitude countries between 2010 and 2019, with this particularly the case in the Mediterranean. The vomitoxin concentrations recorded during the 2018 and 2019 outbreak years, for example, were the highest across the period studied.</p>
<p>Our study did not investigate the causes of this increase. But it is likely that changes in farming practices, climate change, and the dwindling effectiveness of fungicides are all contributing factors.</p>
<p><a href="https://defrafarming.blog.gov.uk/sustainable-farming-incentive-pilot-guidance-use-min-till-or-no-till-farming/">Minimum tillage</a>, where land is cultivated using methods other than ploughing to reduce soil disturbance, is an increasingly popular farming method. The method is beneficial for soil health but leaves crop debris behind and enables the FHB fungus to survive the winter. Maize, a crop highly susceptible to FHB, is also <a href="https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Agricultural_production_-_crops">grown extensively</a> across Europe. Combined, these farming practices increase the FHB pathogen load in the environment. </p>
<p>Climate change may also encourage the spread of FHB disease. Warmer and wetter weather coinciding with when wheat is in flower provides conditions ideal for the FHB fungus to infect and produce mycotoxins.</p>
<p>Resistance to azoles, a commonly used fungicide, has been increasingly <a href="https://www.science.org/doi/10.1126/scitranslmed.3004404?cookieSet=1">reported</a> in recent years. Naturally and through repeated exposure, fusarium fungal species are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8546618/">more resistant</a> to these fungicides than other fungal pathogens. </p>
<p>FHB contamination is widespread across Europe, carrying a substantial cost. Understanding the FHB disease and its mycotoxins is therefore important. But monitoring of FHB outbreaks must be improved to allow researchers to predict which environments are most at risk of mycotoxin-causing fungal diseases in the future. </p>
<p>Methods of containing the disease must also be further developed. These include new fungicides or future crop protection strategies that inhibit the development of mycotoxins. Climate change is leading to more crop disease outbreaks and our need for secure food supplies is increasing, the issue of mycotoxins is therefore only going to become more important.</p><img src="https://counter.theconversation.com/content/196531/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Neil Brown works for the University of Bath. He receives funding from the BBSRC Future Leader Fellowship BB/N011686/1, an internal University of Bath grant, and a Royal Society grant RGS\R2\202128.</span></em></p><p class="fine-print"><em><span>Louise Johns is a PhD student at the University of Bath. Louise Johns was funded by a University of Bath URSA studentship and a British Society for Plant Pathology Covid-19 PhD student support grant.</span></em></p>Wheat is an important global crop, but new research suggests that fungal toxins have contaminated half of all European wheat produced for food.Neil Brown, Senior Lecturer, Molecular Fungal Biology, University of BathLouise Johns, Postgraduate Research Student, Department of Life Sciences, University of BathLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1184062019-06-10T13:27:48Z2019-06-10T13:27:48ZAction is needed to save West Africa’s critically endangered chimpanzees<figure><img src="https://images.theconversation.com/files/278566/original/file-20190608-52741-gnnl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Camera trap image of adult female chimpanzee with her offspring in fallow area in Moyamba district of Sierra Leone foraging on oranges.</span> <span class="attribution"><span class="source">Tacugama Chimpanzee Sanctuary</span></span></figcaption></figure><p>In 2016, the International Union for Conservation of Nature listed the western African subspecies of chimpanzee (<em>Pan troglodytes verus</em>) as “<a href="https://www.iucnredlist.org/species/15935/102327574">Critically Endangered</a>”. It had previously been listed as “Endangered”. </p>
<p>This change of status reflected <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/ajp.22681">dramatic declines in population numbers</a>, of 80% over 24 years. And the outlook for this ape subspecies’ future is not good. The IUCN predicted declines of 6% per annum if threats to the chimpanzees weren’t urgently averted. </p>
<p>These threats are complex. Most of the species lives outside protected areas in West Africa. This means they are susceptible to extinction because of rapid land conversion that’s driven especially by large-scale development projects.</p>
<p>Chimpanzees need wild resources for food and nesting; they mostly eat fruit and typically make a new nest in a tree every night to sleep in. Although chimpanzees are highly intelligent and adaptable, their ability to survive in environments impacted by humans depends on several important factors. </p>
<p>These include how connected different chimpanzee groups are to one another, as well as local, social and environmental conditions. In some areas, chimpanzees are actively hunted for meat, witchcraft and use in traditional medicine. They are also targeted to protect crops and because people fear the animals will harm them. </p>
<p>So are <em>Pan troglodytes verus</em> that live outside protected areas in West Africa doomed? Our <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0215545">recent study</a> suggests that not all hope is lost. We carried out a collaborative research project between <a href="https://research.kent.ac.uk/dice/">the Durrell Institute of Conservation and Ecology Institute in the UK</a>, Spanish academics and the <a href="https://www.tacugama.com/">Tacugama Chimpanzee Sanctuary</a> in Sierra Leone’s Moyamba district.</p>
<p>Among other things, we found that roads are hemming chimpanzees in and affecting their freedom of movement. It also became apparent that some areas in agricultural dominated landscapes should be set aside so that the wild fruiting trees chimpanzee feed on may regenerate. This would stop the chimps from targeting people’s crops. We also suggest that swamps should be conserved as they provide good safe cover for chimpanzees where there is little forest left.</p>
<p>Overall, our findings suggest that conserving chimpanzees in this area will require a mixture of bottom-up approaches involving local people in decision-making processes, as well as top-down strategies. Female chimpanzees only reproduce every five to six years; their populations are slow to recover from decline, most of which are attributable to human behaviour and activity. </p>
<p>People therefore have a moral responsibility to conserve them: not only because they are our closest living relatives and are highly intelligent and sentient beings, but also because they help to manage our ecosystems by dispersing the seeds of fruit trees they ingest.</p>
<h2>Key findings</h2>
<p>One of our key findings related to road infrastructure. We found that even untarred roads in places where chimpanzees are not hunted negatively influence how chimpanzees use their environment. Chimpanzees prefer to roam in areas distant from roads, although they are also known to <a href="https://www.cell.com/current-biology/fulltext/S0960-9822(06)01993-2">cross roads</a> if this is necessary to reach different areas.</p>
<p>This is worrying. <a href="https://www.nature.com/articles/nature13717">More and more roads are expected</a> to be built across West Africa in the coming years. If this isn’t regulated, it could <a href="https://www.stateoftheapes.com/themes/ch-2-impacts-of-infrastructure-on-apes-indigenous-peoples-and-other-local-communities/">dent chimpanzee populations</a>.</p>
<p><a href="https://langint.pri.kyoto-u.ac.jp/ai/en/publication/NicolaBrysonMorrison/Bryson-Morrison2017-IJP.html">Chimpanzees need and prefer forest habitats</a>. But they can also persist in degraded landscapes with limited forest cover, though probably in lower numbers – as long as people tolerate them, and don’t persecute or kill them.</p>
<p>In many areas, the consumption of crops may be a necessity for chimpanzee survival, where wild food resources have been extirpated or are prevented from reaching maturity. Most of the landscape in our case study consists of cultivated fields or fallow areas that can’t regenerate properly. </p>
<p>Their inability to regenerate results from a <a href="https://www.sciencedirect.com/science/article/pii/S0168192311001122">shortening of fallow periods</a> because local human population growth is increasing the pressure on arable land. Without regeneration, key chimpanzee food species such as wild figs cannot reach maturity. That leaves the apes little choice but target people’s crops.</p>
<p>The study also revealed that distance to swamps was a positive predictor of chimpanzee relative abundance. The closer an area was to a swamp, the more chimpanzees used it. Swamps in this region of West Africa are not exploited by communities for agricultural purposes. They’re the only remaining relatively intact habitat type in the study landscape, aside from mangroves.</p>
<p>This suggests that swamps represent safer areas for the chimpanzees. Forest is key for chimpanzees, but where forest tree cover is minimal – in our study area, it was only 1% of the total area – swamps appear to provide a safe haven from humans for chimpanzees and need to be conserved.</p>
<h2>A mix of solutions</h2>
<p>Our findings highlight the need for bottom-up approaches that get local communities involved in conservation initiatives.</p>
<p>We propose that local communities should set aside some critical areas currently used by chimpanzees. That would allow wild fruiting trees to regenerate, which could could help reduce chimpanzees’ reliance on crops for food. This approach would also benefit local people when it comes to harvesting sustainably wild resources, such as medicinal plants, that they told us are no longer available. </p>
<p>Improving agricultural productivity and promoting alternative revenue generating activities could also help to improve people-chimpanzee co-existence. Such activities should be rolled out widely across the region to minimise the influx of people understandably attracted by economic opportunities, putting more pressure on the land and resources. </p>
<p>But top-down initiatives will be important, too. Countries could consider national level <a href="https://www.stateoftheapes.com/themes/industrial-mining-oil-and-gas">Strategic Environmental Assessments</a>. These allow policy makers to understand a country’s biodiversity and balance development, conservation and wellbeing objectives, as well as the cumulative impact of large scale development.</p>
<p>Unfortunately, no country in West Africa has such assessments in place. Nor have any nations in the region put in place effective cross-sectorial legal requirements for <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111671">Social and Environmental Impact Assessments</a> for large scale development projects. Legal frameworks are key: without them, even if an impact assessment exists, it’s of no use as it’s not legally binding.</p>
<p><em>Luna Cuadrado also contributed to this article.</em></p><img src="https://counter.theconversation.com/content/118406/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr. Tatyana Humle, senior lecturer with the Durrell Institute of Conservation and Ecology at the University of Kent, UK, received funding as Principal Investigator from the Arcus Foundation for this project.</span></em></p><p class="fine-print"><em><span>Rosa Garriga 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>Studies show that West Africa’s critically endangered chimpanzees are finding ways of adapting to their rapidly changing habitat, but they still remain highly at risk.Tatyana Humle, Senior Lecturer in Primate Conservation, University of KentRosa Garriga, Field researcher, Universitat Autònoma de BarcelonaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1014872018-08-21T13:44:29Z2018-08-21T13:44:29ZBeehive fences and elephants: Tanzanian case study offers fresh insights<figure><img src="https://images.theconversation.com/files/232316/original/file-20180816-2921-qeju5y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Beehive fences can help improve human-elephant coexistence.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>When people cultivate food crops on or near wild lands it can be assumed that wild animals will eat them – what’s known as crop-raiding. Farms in the vicinity of protected areas can expect to be visited by a range of wild animals including birds, rodents, and large mammals like <a href="https://www.tandfonline.com/doi/full/10.1080/10871209.2014.853330">monkeys</a>, bushpigs and <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0178840">elephants</a>. </p>
<p>Because of their size, elephants are the most conspicuous crop-user and may, in addition to eating crops, trample farmers’ fields and break fences. Using nonlethal ways to deter elephants from farms is the most humane and effective defence long-term. But elephants are still being shot and killed, particularly if they threaten people or property. </p>
<p>Given that elephant numbers are dwindling, creative solutions need to be found to reduce crop losses and improve the chances of elephants and people coexisting. </p>
<p>Over the past eight years we have been trying to do just that. We have been <a href="http://www.stzelephants.org/">collecting data</a> on elephants – their consumption patterns and their impact on crops at a forested site in southern Tanzania. And we’ve been working with farmers to try and design ways of keeping elephants at bay. </p>
<p>After some failures, we imported an idea from Kenya – beehives. After five years of study we’ve published our <a href="https://www.cambridge.org/core/journals/oryx/article/efficacy-of-beehive-fences-as-barriers-to-african-elephants-a-case-study-in-tanzania/589D8AE1D72A41BDDC124062A12D9C7A">results</a> which show that there is indeed merit to installing fences made up with beehives to keep elephants from eating, and destroying, farmers’ crops.</p>
<h2>What failed, what worked</h2>
<p>One method farmers tried to adopt involved collecting and soaking elephant dung in buckets of water and spreading the fibrous mixture across their fields. The basis of this interesting idea was that elephants are coprophobic – they don’t like their own poo – and will avoid eating crops covered in their own dung. </p>
<p>We were unable to test the effectiveness of this approach because Udzungwa Mountains National Park introduced new rules in 2011 that banned people from collecting firewood as well as non-timber products such as elephant dung from the park. </p>
<p>Farmers then tried chilli-oil. Cloth, soaked in used motor oil and powdered chillies, was then attached to rope fences. But heavy rains in the Udzungwa Mountains meant that the mixture had to be reapplied regularly. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/232314/original/file-20180816-2909-1agcfku.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">Beehive fences can help reduce elephants’ damage to crops.</span>
<span class="attribution"><span class="source">Author supplied</span></span>
</figcaption>
</figure>
<p>Next we looked to our neighbours for a solution – beehives. These were being used in <a href="http://elephantsandbees.com/">elephant conservation field programmes in Kenya</a> and the practice was spreading to other African countries and also to Asia. </p>
<p>Using beehives at our site involved installing a fence between the park boundary and farms. The beehives are connected with a wire. When elephants attempt to enter fields they disturb the wire which causes the hives to swing. This in turn disturbs the bees inside the hives. Our initial short 500m fence of 50 hives was eventually extended by 600m and 87 hives four years ago. </p>
<p>Our findings after five years of study show that there’s promise in the approach.</p>
<h2>Our findings</h2>
<p>Our main finding was that the probability of elephants damaging crops was less with the construction of the short beehive fences, and even lower when the fence was extended. </p>
<p>We also found that as more hives making up the fence were inhabited by bees, the more elephants stayed away. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/XAEWcPrmd7c?wmode=transparent&start=6" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Beehive fences and elephants.</span></figcaption>
</figure>
<p>A few factors affected the success of the beehive fences. These included:</p>
<ul>
<li><p>Elephants breaching the fence where hives were empty. Of the 133 fence breaches, nearly 70% were between empty hives.</p></li>
<li><p>Not mending damaged fences promptly.</p></li>
<li><p>Elephant bulls visiting farms at night, when bees are relatively less active.</p></li>
</ul>
<p>The beehive fence didn’t completely eliminate elephants entering farms. But it did reduce the number of elephant visits and was well-received by farmers. </p>
<p>Another indicator of success was that farmers stopped calling game officers to shoot problem elephants. Farmers also formed and registered a cooperative group to manage the beehive fence and honey harvests.</p>
<h2>The beehive fence method is spreading</h2>
<p>The use of beehive fences is beginning to spread across southern Tanzania. And government has recently advised that beehives be used to deter elephants from crops <a href="https://www.ippmedia.com/en/news/%C2%A0tanapa-tfs-ordered-initiate-%C2%A0beekeeping-projects-ten-villages">around the Serengeti</a>, in northern Tanzania. </p>
<p>Next steps should involve standardising how sites employing this method are monitored and evaluated. This could help determine the minimum effective fence length and optimal placement of beehives. </p>
<p>Other lessons could be learnt that might be replicated in new sites. For example, unoccupied – or dummy hives – have been shown to be effective but presumably only if elephants have already developed a negative association with occupied ones. </p>
<p>Finally, researching the differences in the relative nighttime activity of both elephants and honeybees across sites could also help explain differences in outcomes and inform best deterrent approaches and improvements. </p>
<p>Our programme has already pioneered the use of camera traps to monitor elephant activity and identify <a href="https://www.cambridge.org/core/journals/oryx/article/using-camera-traps-to-study-the-agesex-structure-and-behaviour-of-cropusing-elephants-loxodonta-africana-in-udzungwa-mountains-national-park-tanzania/AAB225F1915E73FAF278B8B2F5BA7E56">crop-using individuals</a> in the vicinity of beehive fences. These could be used at other sites too.</p><img src="https://counter.theconversation.com/content/101487/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The Southern Tanzania Elephant Program (STEP), with which Katarzyna Nowak is affiliated, has received funding from the U.S. Fish and Wildlife Service African Elephant Conservation Fund including for the beehive fence initiative. The first 50 beehives were funded by the Fauna and Flora International Rapid Response Facility; subsequent hives had support from Raleigh International. Katarzyna Nowak is currently a fellow with The Safina Center, a research associate in Zoology and Entomology at the University of the Free State (Qwaqwa campus) and on contract with the Wildlife Conservation Society-Americas Program. </span></em></p>There is indeed merit to using beehives to keep elephants from eating and destroying crops.Katarzyna Nowak, Fellow at The Safina Center, University of the Free StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/798652017-08-02T15:45:02Z2017-08-02T15:45:02ZWhy controlling rats on small-scale African farms is vital for food security<figure><img src="https://images.theconversation.com/files/180505/original/file-20170801-21062-ppzt0i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In many parts of Africa rodents often cause crop losses.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><a href="http://www.pnas.org/content/113/52/14964.short">Recent analysis</a> suggests that Africa will only be able to achieve food security if it invests in crop intensification like increased fertiliser and pesticide input per hectare. But the expansion of agricultural production areas can also improve this. </p>
<p>A complicating factor in African agriculture is that most of the production comes from relatively <a href="http://www.sciencedirect.com/science/article/pii/S0305750X15002703">small farms</a>. Most of these are less than 2 hectares in size. This is much smaller than in Europe and the Middle East where most farms are greater <a href="http://ec.europa.eu/eurostat/statistics-explained/index.php/File:Distribution_of_holdings_and_utilised_agricultural_area_by_size_class_(utilised_agricultural_area),_EU,_2005_and_2010.png">than 10 hectares</a>. In Latin America most farms <a href="http://www.globalagriculture.org/report-topics/industrial-agriculture-and-small-scale-farming.html">exceed 50 hectares</a>.</p>
<p>This means that addressing issues that affect small scale farmers’ productivity can play an important role in food security. Most farmers simply can’t afford pest management control. Often, these methods are lacking in rural areas. And where there are products it can be adulterated or misused. </p>
<p>Agricultural pests are one of the key factors affecting small holder farmer production. In many parts of Africa large population outbreaks of rodents occur often and can sometimes lead up to <a href="http://books.irri.org/9789712202575_content.pdf">100% crop loss</a>. Rodents can damage nearly every crop people try to grow. It’s often difficult to measure chronic damage because it happens over the entire growing season and even after the crop is harvested.</p>
<h2>The neglected rodents</h2>
<p>Efforts to control pests face a number of challenges. Firstly, management is often limited, because of the high cost of herbicides, insecticides and rodenticides. On top of this they aren’t readily available in local farming areas. And most pest control focuses on invertebrate pests like stem borers, armyworm and locusts. Very little attention is paid to vertebrate pests like rodents or birds like the <a href="http://www.irinnews.org/news/2009/08/19">red-billed quelea</a> (<em>Quelea quelea</em>).</p>
<p>Rodents are a particularly important group of pests. Agriculturally, they can inflict considerable economic damage because of their abundance, diversity, feeding habits and high reproduction abilities. </p>
<p>Research on rodent pest control tends to be neglected. But some community based development programmes are looking at how rodents can be controlled using <a href="http://projects.nri.org/ecorat">ecological methods</a>. <a href="https://www.youtube.com/watch?v=nWTC9ZE25EQ">Ecologically-based rodent management</a> involves, firstly, increasing our understanding of their population biology, social behaviour, taxonomy and community ecology. These insights can then be used to develop effective and sustainable management strategies. This approach has been effective in reducing pest damage as well as <a href="http://www.sciencedirect.com/science/article/pii/S1573521404800113">reducing reliance on rodenticide poisons</a> in many countries. </p>
<p>There is little data on the effects of pest control on rodents, particularly when it comes to small holder farming systems. To gain a better understanding we did a <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0174554">systematic review</a> on the effect of rodent pests on small holder farming in Africa and the island nation of Madagascar. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=447&fit=crop&dpr=1 600w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=447&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=447&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/180573/original/file-20170801-22175-4pbx7v.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=562&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 damage to maize caused by rats.</span>
<span class="attribution"><span class="source">Author supplied</span></span>
</figcaption>
</figure>
<h2>Rodent management in Africa</h2>
<p>Our review highlighted several important findings. We found median crop losses (midpoint of reported losses) attributed to rodent pests were around 15%. This has a significant impact on small holder grain yields and is comparable to losses from cereal stem borers in Africa where much greater investments have been made in <a href="http://onlinelibrary.wiley.com/doi/10.1111/een.12216/full">control programmes</a>.</p>
<p>But there was a big discrepancy in estimated and reported losses, which highlights the importance of standardising research protocols. For example, very little research has been done to try and find a link between rodent density to crop impact. This limits the setting of reasonable management thresholds on when to control rodents based on their density. </p>
<p>Most importantly, we found a paucity of research investigating effectiveness of control measures on rodent pests.</p>
<p>We made several detailed recommendations that we feel will improve the robustness of rodent pest research. The most important ones included the fact that researchers must adopt a “meta-analytic” <a href="https://link.springer.com/chapter/10.1007/978-3-319-55895-0_25">framework</a>. For example, they must place their study in the context of prior literature and they must report on the effect of rodent control, particularly making the comparison between studies and strategies more explicit. This framework has been successfully applied to other evidence based research fields <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049418">like medical research</a>. </p>
<p>Another was that researchers and funding organisations must be encouraged to establish and fund <a href="https://academic.oup.com/bioscience/article-abstract/67/3/271/3057250/Long-Term-Studies-Contribute-Disproportionately-to?redirectedFrom=fulltext">long-term studies</a>. Once a firm foundation has been established on understanding the drivers of population cycles of the dominant rodent pest species, other important aspects like management and community ecology can be successfully developed. </p>
<p>For example, in some African countries – like Tanzania – there have been great improvements in understanding the ecology of pest rodent species. Researchers showed that rainfall plays an important role in predicting rodent pest outbreaks. This facilitated regional planning to control rodent pests in agricultural areas. </p>
<p>We also found that researchers must focus more on empirical treatment control studies that test a management action compared to no management actions. These must be done with suitable replication that investigates management actions on rodent pest populations and associated crop losses. For example, our <a href="http://www.sciencedirect.com/science/article/pii/S1049964416301256">recent meta-analysis showed</a> that avian predators, like barn owls, can reduce rodent pests.</p>
<p>Lastly, we suggest that ecologically based rodent management activities and research should be carried out by multidisciplinary and interdisciplinary teams. In this way research can be sustained over a longer period if there’s collaboration, knowledge is transferred and communities are involved.</p><img src="https://counter.theconversation.com/content/79865/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lourens Swanepoel receives funding from Sasol Agricultural Trust (South Africa), International Foundation for Science (D/4984-2), European Union through its ACP S & T programme (StopRats; FED2013-330223; <a href="http://www.acp-hestr.eu/">http://www.acp-hestr.eu/</a>). He is affiliated with the African Institute for Conservation Ecology and Genetics (AICEG) (Not for profit organization).</span></em></p><p class="fine-print"><em><span>Steven Belmain currently receives funding from the McKnight Foundation, the European Development Fund and the Netherlands Organisation for Scientific Research.</span></em></p>Agricultural pests are one of the key factors affecting small holder farmer production. Focus is normally put on invertebrate pests, but rodents can do severe damage to crops as well.Lourens Swanepoel, Associate lecturer, University of VendaSteven Belmain, Professor of Ecology, University of GreenwichLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/811492017-08-01T17:58:42Z2017-08-01T17:58:42ZWhat camera traps tell us about elephants eating crops<figure><img src="https://images.theconversation.com/files/179317/original/file-20170723-28465-536uzm.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Southern Tanzania Elephant Program used camera traps to capture elephant visits to farmland.</span> <span class="attribution"><span class="source">STEP/Author supplied</span></span></figcaption></figure><p>An important conservation goal is to try and ensure that people and wildlife can coexist. This is especially important when it comes to elephants, whose large home ranges and long distance movements take them outside of <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3008.2000.00092.x/full">protected areas</a>.</p>
<p>One of the major challenges to coexistence is the use of food crops by elephants. This threatens the <a href="http://wwf.panda.org/what_we_do/endangered_species/elephants/human_elephant_conflict.cfm">livelihoods, food security</a> and <a href="http://www.sciencedirect.com/science/article/pii/S0006320712003345">well-being</a> of rural communities. Elephant forays into farmland sometimes results in <a href="https://www.researchgate.net/profile/Richard_Hoare/publication/278051645_Lessons_from_15_years_of_human-elephant_conflict_mitigation_Management_considerations_involving_biological_physical_and_governance_issues_in_Africa/links/557bde4808aeea18b7751990/Lessons-from-15-years-of-human-elephant-conflict-mitigation-Management-considerations-involving-biological-physical-and-governance-issues-in-Africa.pdf">retaliatory and legal killings under the Problem Animal Control laws</a> and erosion of support for elephant conservation efforts.</p>
<p>For people and elephants to thrive in the long-term, it’s important to find ways to mitigate the impact of the animal on people’s lives and livelihoods, and vice versa. To find effective solutions, we need to understand why elephants eat crops rather than fodder from the bush and how they learn about crops as a source of food.</p>
<p>To explore these questions our team at the <a href="http://www.stzelephants.org/">Southern Tanzania Elephant Program</a> used camera traps to capture elephant <a href="https://www.cambridge.org/core/journals/oryx/article/using-camera-traps-to-study-the-agesex-structure-and-behaviour-of-cropusing-elephants-loxodonta-africana-in-udzungwa-mountains-national-park-tanzania/AAB225F1915E73FAF278B8B2F5BA7E56">visits to farmland</a>. The cameras were set up in an area adjacent to the Udzungwa Mountains National Park in Tanzania between 2010 and 2014. </p>
<p>We placed camera traps on elephant trails on the National Park boundary to photograph elephants as they travelled in and out of neighbouring farmland. We then studied the camera trap photos to identify individual elephants from key distinguishing features like ears and tusks.</p>
<h2>High-risk, high-reward</h2>
<p>All the elephants photographed by our camera traps were males. This is consistent with <a href="https://academic.oup.com/beheco/article/22/3/552/269150/No-risk-no-gain-effects-of-crop-raiding-and">previous studies</a> suggesting that eating crops is a high risk, high reward feeding strategy for males. Females have been <a href="https://anotherbobsmith.files.wordpress.com/2013/02/smith_kasiki_00_hec.pdf">documented</a> to feed on crops, but they are generally less likely to visit farms because of the risks involved to their young.</p>
<p>Age also plays a role. Our study, as well as previous studies in <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0031382">Amboseli, Kenya</a> and <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2028.2005.00577.x/full">Kibale, Uganda</a> found that eating crops appears related to specific <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0031382">milestones</a> in a male elephant’s life. </p>
<p>Two particular milestones stood out: the start of reproduction in bulls when they reach the ages of between 20-30 years, and their reproductive peak years in their 40s. When males reach these milestones, they are more willing to take risks and have increased energetic demands. Crops are an attractive source of food for males seeking to maximise their <a href="https://academic.oup.com/beheco/article/22/3/552/269150/No-risk-no-gain-effects-of-crop-raiding-and">body size and reproductive success</a>. </p>
<p>How do males learn about crops as a food source? In Udzungwa, we found that young bulls aged 10-14 years visited farms. This is the age when males typically leave their maternal family groups, so they may be discovering farms during the process. It’s also possible that they learn about crops from older elephants. <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0031382">Researchers in Amboseli</a> found that young bulls learnt about crops from older bulls and that male social networks shaped behaviour.</p>
<h2>How many eat crops?</h2>
<p>Some <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2011.01967.x/full">studies</a> have investigated how many bulls eat crops, and how their feeding habits vary. In Udzungwa we identified 48 different elephants from our camera trap photos. With so many bulls visiting the farmland in our study site, we couldn’t attribute the crop damage to just a few habitual males. </p>
<p>We also found that the frequency of visits varied between individual bulls. Two-thirds were seen only once over the four-year study period, suggesting that these bulls visit farms infrequently. One-third of the bulls were seen multiple times and 18% more than twice over the study period. These males may be using crops more regularly. But even among these repeat offenders, males varied considerably in how often they visited farms. </p>
<p>In Kenya by comparison, researchers estimated that 12% of Amboseli bulls and 21% of bulls from the wider Amboseli, Kilimanjaro and Tsavo-Chyulu populations <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2664.2011.01967.x/full">were repeat crop eaters</a>. Combined, this evidence suggests that the majority of bulls occasionally use crops, while a small proportion may use them more frequently. </p>
<h2>Strategies</h2>
<p>Strategies to reduce crop losses to elephants should consider that most bulls consume crops infrequently. So, killing elephants for eating crops is unlikely to significantly reduce crop loss. Taking lethal action is also costly, for it affects those older bulls who are more likely to be eating crops. Killing these older bulls removes a crucial source of <a href="http://news.nationalgeographic.com/2015/10/151017-zimbabwe-elephant-tusker-trophy-hunting-poaching-conservation-africa-ivory-trade/">ecological knowledge as well as important breeding individuals</a>. This is particularly damaging to elephant populations already under threat from ivory poaching. </p>
<p>There are much better non-lethal options for reducing crop losses to elephants. These include <a href="http://onlinelibrary.wiley.com/doi/10.1111/cobi.12898/full">beehive fences</a> and land use planning which involves carefully assessing land for the best possible use. These approaches require strong commitment, community buy-in and creativity. But, as we’ve found in our <a href="http://www.stzelephants.org/projects/human-elephants-co-existence/">work</a> in Tanzania, they offer promising avenues for improving the chances of farmers and elephants being able to coexist.</p><img src="https://counter.theconversation.com/content/81149/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Josephine B. Smit and co-authors received funding from the US Fish and Wildlife Service, Idea Wild, Yale University's Summer Environmental Fellowship, and Richter Summer Fellowship to conduct the study described in the article. She is a PhD student at the University of Stirling and works for Southern Tanzania Elephant Program.</span></em></p>Elephants feeding on crops poses a challenge to their coexistence with humans. Farmers must introduce strategies to reduce losses and avoid lethal action against the endangered species.Josephine B. Smit, PhD Candidate, University of StirlingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/728222017-02-12T10:02:10Z2017-02-12T10:02:10ZArmyworms are wreaking havoc in southern Africa. Why it’s a big deal<figure><img src="https://images.theconversation.com/files/156373/original/image-20170210-23342-hnp6tx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Fall Armyworm has a devastating impact because it eats the reproductive parts of the plant as well as its leaves.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><em>A combination of native African armyworms and Fall armyworms from the Americas are ravaging staple crops <a href="http://www.timeslive.co.za/sundaytimes/businesstimes/2017/01/29/Biblical-plague-stalks-SA-maize">across southern Africa</a>. If uncontrolled, they have the potential to cause major food shortages. The Conversation Africa’s energy and environment editor Ozayr Patel asked Kenneth Wilson to explain the threat and what can be done about it.</em></p>
<p><strong>What are armyworms, where do they come from and how do they travel?</strong></p>
<p>Armyworms are the caterpillar stage of moths belonging mainly to the genus <em>Spodoptera</em>. They are called armyworms because when they have ravaged a crop they march along the ground like a vast army of worms in search of more food. There are at least eight countries in southern Africa that have been hit by outbreaks of armyworms.</p>
<p>This sequence of outbreaks began in mid-December <a href="https://www.lusakatimes.com/2016/12/29/army-worms-invade-chipata-area/">2016 in Zambia</a> and has spread rapidly ever since. It is now as far south as South Africa. Because armyworms feed on many of the staple food crops they have the potential to create food shortages in the region.</p>
<p>The recent outbreaks in southern Africa appear to be a combination of the native African armyworm (<em>Spodoptera exempta</em>) and a new invasive species called the Fall armyworm (<em>Spodoptera frugiperda</em>). This new species is endemic to tropical and subtropical regions of Central and South America, where it causes considerable damage to maize and other crops.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=454&fit=crop&dpr=1 600w, https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=454&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=454&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=570&fit=crop&dpr=1 754w, https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=570&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/156367/original/image-20170210-23342-ggcz0c.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=570&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 top photo shows a mature maize field before pests arrive. The bottom photo shows a similar field following an armyworm attack.</span>
<span class="attribution"><span class="source">Top: Ken Wilson; Bottom: FAO Lesotho</span></span>
</figcaption>
</figure>
<p>The Fall armyworm was first formally identified as being on the continent as recently <a href="https://www.plantprotection.org/Portals/0/documents/Newsletters/2016/IAPPS2016-10.pdf">as January 2016</a> in <a href="http://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0165632">West Africa</a>, including Nigeria and its neighbours. </p>
<p>It is unclear how it reached Africa from the Americas but it’s likely it arrived on imported plants. It’s also possible that it migrated across the Atlantic on favourable winds over multiple generations. </p>
<p>It is not yet known whether the recent outbreaks in southern Africa are derived from the earlier West African ones. But Fall armyworms are known to be strong migrants in the Americas. Every year Fall armyworms fly <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3434929/">from Mexico and the southern states of the US to Canada</a>. </p>
<p><strong>What makes them so devastating?</strong></p>
<p>Both African and Fall armyworms do most damage to the staple cereal crops such as maize, wheat, sorghum, millet and rice. They also eat pasture grasses which has an impact on livestock production. </p>
<p>The African armyworm – they can be 3cm long – can reach densities as intense as 1000 caterpillars per square metre, quickly razing crops to the ground. On maize, the number of caterpillars per plant is, of course, much lower but it can cause just as much of an impact. The insects strip the leaves of even mature maize plants bare.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=404&fit=crop&dpr=1 600w, https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=404&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=404&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=508&fit=crop&dpr=1 754w, https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=508&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/156365/original/image-20170210-23361-173xa0q.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=508&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Right: African armyworm Left: Fall armyworm.</span>
<span class="attribution"><span class="source">Ken Wilson</span></span>
</figcaption>
</figure>
<p>Unlike their African cousins, the Fall armyworm also feeds on a range of non-cereal crops. Nearly 100 different host plant species have been recorded. These include cotton, soybeans, groundnut, peanut, potato, sweet potato, spinach, tomato, sweet peppers, cabbage and tobacco. </p>
<p>Damage to maize is likely to have the biggest impact on farmers in southern Africa because it’s the main staple food crop <a href="http://www.iita.org/maize">in the region</a>. </p>
<p>The impact of the Fall armyworm is likely to be devastating because it eats the leaves of the plant as well as its reproductive parts. This damages or destroys the maize cob itself.</p>
<p><strong>Where have the most devastating attacks occurred? What was the result?</strong></p>
<p>In 2012-2013 the African armyworm cut Zambia’s <a href="https://www.bloomberg.com/news/articles/2017-01-03/zambia-battles-ravaging-armyworms-that-threaten-food-security">maize production by 11%</a>. The latest outbreaks could lead to losses of up to <a href="http://paulshalala.blogspot.co.za/2017/01/zambia-may-lose-40-maize-this-year-due.html">40%</a> as an estimated 124,000 hectares of maize has been <a href="http://www.bizcommunity.com/Article/196/650/156440.html">attacked</a>.</p>
<p>In neighbouring Zimbabwe, seven out of eight maize-producing provinces have had armyworm outbreaks, and in Malawi at least 9,000 hectares <a href="http://www.bizcommunity.com/Article/196/650/156440.html">have been attacked</a>. Figures are not yet available for the other five southern African countries currently affected.</p>
<p><strong>What are the potential economic consequences if the problem is not arrested?</strong></p>
<p>It is too early to say what the impact will be on food production in the region. Chemical pesticides have been mobilised in most countries, though their efficacy has been questioned. In Brazil, where armyworms can breed all year round, controlling them <a href="https://www.bloomberg.com/news/articles/2017-01-16/alien-armyworms-invade-corn-in-drought-hit-southern-africa">costs an estimated US$600 million a year</a>. The cost of control in southern Africa hasn’t been determined yet. </p>
<p>But it’s likely to be substantial given that many litres of imported chemicals have already been bought by countries desperate to protect their crops. This means that even if control proves to be effective it will have been costly. </p>
<p>The economic consequences could be severe if the Fall armyworm persists and spreads throughout the sub-Saharan Africa region.</p>
<p><strong>What is the best way to stop them damaging crops?</strong></p>
<p>Chemical pesticides can be effective against both armyworm species. But resistance to many chemicals is an issue for the Fall armyworm throughout <a href="http://www.sciencedirect.com/science/article/pii/0048357591902169">its native range</a>. It’s not known whether there is pesticide resistance in the Fall armyworms blighting southern Africa. </p>
<p>The variable efficacy may be due to genetic resistance, or it might be as a result of the way in which the spray is applied. The Fall armyworms are often inaccessible to insecticides because of their tendency to hide in the whorls and reproductive parts of the host plant. </p>
<p>Research is needed to work out which chemical is the best to control the strain of Fall armyworm in southern Africa. </p>
<p>But there are alternative approaches. </p>
<p>In parts of their native range in the Americas, genetically-modified Bt maize is grown to combat the Fall armyworm. This may also be an option for South Africa and some other countries where GM crops are already grown. But many parts of Africa do not allow or welcome GM varieties. And Fall armyworm has also evolved resistance to some Bt toxins, with some evidence <a href="https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1143_21.pdf">for cross resistance</a>.</p>
<p>There are non-chemical, <a href="https://www.epa.gov/pesticides/biopesticides">biological pesticides</a> that could also be effective. These are pesticides derived from natural diseases of insects, such as viruses, fungi and bacteria. I have been involved in the development of a highly effective biopesticide against African armyworm in Tanzania. But this still needs to go through the commercialisation and registration process, which is both <a href="http://www.foodsecurity.ac.uk/blog/2017/01/natural-killers-developing-better-biopesticides/?platform=hootsuite">costly and time consuming</a>. </p>
<p>A similar biopesticide has also been developed against the Fall armyworm, but again this is not yet registered for use in Africa.</p>
<p>Biopesticides tend to be effective against a much narrower range of species than chemicals, which is good for the environment. But it means that they can only be used for a limited number of pests, often making them more expensive than chemicals.</p>
<p>There are also some other indigenous approaches that could be effective. This includes the use of local plant extracts like <a href="https://static1.squarespace.com/static/52f220cbe4b0ee0635aa9aac/t/53d8f8d6e4b03775e0dd5a17/1406728406049/tephrosia+vogelii.pdf">Tephrosia vogelli</a> and <a href="http://www.webmd.com/vitamins-supplements/ingredientmono-577-neem.aspx?activeingredientid=577&">neem</a>, to produce botanical pesticides, and the addition of sand to maize whorls where armyworms are feeding.</p>
<p>Only time will tell what the full impact of this armyworm invasion will have.</p><img src="https://counter.theconversation.com/content/72822/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Professor Wilson currently receives funding from the UK’s Biotechnology and Biological Sciences Research Council and Innovate UK.</span></em></p>A combination of armyworms native to Africa and those normally found in the Americas are ravaging crops in sub-Saharan Africa.Kenneth Wilson, Professor at the Lancaster Environment Centre, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.