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Worm turns for cotton pest as Australia breeds in resistance

Among Australia’s key cotton pests is the global insect nemesis of agriculture, Helicoverpa armigera. More commonly known as a bollworm, the larvae of this beast munch on precious crops in Asia, Europe…

Cotton is under constant attacks from rapidly evolving pests. CSIRO

Among Australia’s key cotton pests is the global insect nemesis of agriculture, Helicoverpa armigera. More commonly known as a bollworm, the larvae of this beast munch on precious crops in Asia, Europe, Africa and Australia, causing damage estimated at greater than US$2 billion each year. The bollworm’s weapon is simple: it rapidly evolves resistance to insecticide sprays.

Insects fight back

To tackle the problem, in the mid-1990s Australian cotton breeders began incorporating Bt insect resistance genes in their varieties. “Bt cotton” plants dispatch an insecticide from a bacteria – Bacillus thuringiensis (Bt) – that is toxic to the bollworm.

The advantages of using Bt cotton over non-Bt varieties are huge. Since introducing it over a decade ago, there has been an 80% reduction in the use of chemical pesticides previously required to control bollworms. This not only means safer working operations for growers but is beneficial for the environment as well.

But a recent US-French study published in the journal Nature Biotechnology indicates that harmful crop pests are becoming resistant to the most popular type of genetically-modified, insect-repellent crops.

The researchers reviewed data from 77 studies across eight countries and found five of 13 examined pest species have a degree of in-field resistance to the bacterial insecticide. In 2005, it was just one.

Insecticides from bacteria have been engineered into crop plants to thwart pests like Australia’s Helicoverpa armigera. CSIRO

If we don’t manage the resistance of pests to Bt crops, insects like our very own bollworm could get back to damaging our agricultural industry sooner than predicted.

Outsmarting the bollworm

Australian agriculture is uniquely positioned to prevent Bt resistance. Unlike some of the countries in the study, we have developed evidence-based strategies to delay pests' resistance to Bt cotton - and farmers must use them. In Australia, cotton growers must plant non-Bt refuges. “Refuges” provide a home for non-resistant pests to breed. Because of the way most Bt resistances function, when a resistant insect mates with a non-resistant partner, the resulting offspring is non-resistant. So planting refuges ultimately serves to dilute any in-field resistance.

The Australian strategy also attacks the hibernation tactic of bollworms. Growers must cultivate the soil under Bt cotton to kill any resistant pupae during the winter.

The final pillar in the strategy requires farmers to plant their crop in a short window of time. This minimises the period the insects have to build resistance through exposure to the cotton expressing the bacterial insecticide.

But has it worked?

For the past decade, CSIRO has monitored populations of Australian pests to determine how well this strategy is working. As over 90% of the local industry now grows Bt cotton, there is enormous selection pressure for insects to develop resistance. Furthermore, even before genetically engineered crops were grown in Australia, our bollworms carried genes that predisposed them to resisting some of the Bt toxins engineered into the cotton.

Despite this, results indicate that Australian pests have not developed field resistance. There has been an increase in the proportion of bollworms carrying a resistance gene for one of the bacterial insecticides in current varieties. But overall, less than 1% of Australian pest populations carry the two copies of this gene that are required for them to be resistant. Furthermore, insects that carry resistance genes against both of the bacterial insecticides in current varieties of cotton are exceptionally rare.

While the US-French study indicates pests like our own bollworm may be building resistance to Bt cotton, the mitigation plans adopted by the Australian cotton industry are ensuring it remains one step ahead of insect beasts like Helicoverpa armigera.

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28 Comments sorted by

  1. Will Hunt

    Farmer

    15 or 20 years seems to be what you will get ot

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    1. Will Hunt

      Farmer

      In reply to Will Hunt

      Damn iPad. Just saying, 15 or 20 years seems to be what you might get out of a GM crop before the laws of nature kick in and something turns up that finds it tasty. 15 or 20 years is but the blink of an eye in the evolution of cotton, and yet Monsanto et al are presenting GMs as the universal panacea for the future.
      I have my doubts. Seems to me that humanity is painting itself into a corner. Everyone wants cheaper food, and no one wants to grow it.
      So we have farmers that are getting older and older, farms are getting bigger and bigger, and what the world really needs is more , younger farmers spending more time per acre making sure things are done properly.
      Instead it's the other way round.

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    2. John Doyle

      architect

      In reply to Will Hunt

      Yes, Will
      We are being more cautious than in the USA and Canada
      and we do require labelling.
      But vigilance is mandatory I think

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    3. Will Hunt

      Farmer

      In reply to John Doyle

      John

      GM is a huge topic, unfortunately it has been hi-jacked by Monsanto and Roundup Ready which is unfortunate. There may be a legitimate use for GM in introducing drought, salt or heat tolerance into existing food crops which may delay the inevitable cataclysmic food crisis for a few years.
      My main concern is that glyphosate (Roundup) is a very useful tool for the purpose for which it was invented, which is to kill all your weeds before you plant a crop, instead of cultivating. The improvement…

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    4. John Doyle

      architect

      In reply to Will Hunt

      No I'm not up on the science, Will.
      The video says glyphosate is a chelating agent and it depletes soil organisms. I understand that avoiding cultivating preserves the soils from blowing away. Soil degradation is the second environmental danger after excess population growth.
      http://www.sciencedaily.com/releases/2006/03/060322141021.htm
      Do you know this Cornell university study?
      Have you heard Monsanto do not use GMO food in its canteens?

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    5. Will Hunt

      Farmer

      In reply to John Doyle

      John,

      Not sure how to illustrate the difference between how we use glyphosate, which is to blow all your weeds out of the ground before you then plant your crop, and the GM way which is to keep spraying yr crop with glyphosate whilst its growing.
      I have no evidence to back it up but definitely our soil structure has improved since we went to minimum till, of which of course glyphosate is an important part.
      A lot of no-til livestock free farms are using glyphosate 3 or more times per year to control over summer weeds which is a worry. Summer rains are becoming increasingly important with the vagaries of climate change.
      Its a bit of a worrry. We are in uncharted waters

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    6. Will Hunt

      Farmer

      In reply to Will Hunt

      Interestingly ( I think) at a meeting of some hundreds of farmers at the Birchip Cropping group in February, a confidential survey of growers revealed that only 3 people were intending to plant GM canola. (Birchip is in Victoria where GMs are legal)
      Everyone who has tried it says its a rubbish performer and expensive to grow

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    7. John Doyle

      architect

      In reply to Will Hunt

      Canola, aka modified rapeseed, is a rubbish crop.
      It is made into a "vegetable oil"which is an off topic discourse here.
      But which we should not be consuming.
      The yellow fields do look pretty, just as do the purple pattersons curse paddocks in October.

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    8. Will Hunt

      Farmer

      In reply to John Doyle

      As the subject about is as much about GM & resistance as cotton, I think it is barely off topic if at all.
      3 points: Canola specifically is vegetable rapeseed which has been selected for low euricic acid in the oil. Most canola ISN"T GM.
      Canola, being a poor host to soil borne root diseases has a natural 'fumigating' effect on soil so it is an extremely good break crop (you grow your best cereals after canola)
      Canola oil, as well as being used in margarine, cooking oil and the manufacture of paints, plastics, lubricants etc can also be used in a very unrefined state to power diesel motors, so its hardly a 'rubbish' crop.

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    9. John Doyle

      architect

      In reply to Will Hunt

      It's a rubbish crop when it comes to food. Good to see it has some uses though. Still, you might be better off planting legumes?

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    10. Will Hunt

      Farmer

      In reply to John Doyle

      Getting ahead of yourself John,
      Pasture, then Canola (contol of soil borne root diseases); Then a cereal; THEN a legume (beans or peas)
      then another cereal, then back to Pature.
      No nitrogen fertilizer needeed.
      well thats what we do anyway
      Sorry its off topic, but you did ask

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    11. John Doyle

      architect

      In reply to Will Hunt

      That's OK Will, it's good to hear from someone who has hands on knowledge.
      I'm no expert, just curious about growing crops that seem to be using up valuable land for non food purposes, like ethanol.
      I suppose we can always reduce these when the time comes as long as the soils are still viable.
      Apparently already we grow enough food for 9 billion people, but can it be repeated well into the future?

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    12. Will Hunt

      Farmer

      In reply to John Doyle

      good question John.
      A few short decades ago my G-Grandpa made his fortune breeding horses. And the other G-Grandpa on my mothers side grew hay for chaff. They also had cereal crops, cattle and sheep as well of course, but between them they grew, using pasture and solar energy, food, fibre, engines and fuel.
      Then along came Messers Ford, DuPont, and Shell Oil and reduced them to growing only food.
      One trick farming is a very new phenomenon, and it's completely dependent on fossil fuels.
      I am very aware of that.
      Did you know that some of the big farms in the Victoria Mallee had upwards of 80 to 100 horses for draft work, and the rule of thumb for the grain you hold back to keep the horses going was 1/3 of the crop? Trouble with horses you still have to feed them whether they are working or not.
      I figure I could crush enough diesel fuel from Canola oil to be self sufficient off of about 40 hectares.
      Still, we are a long way from GM cotton now.

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    13. John Doyle

      architect

      In reply to Will Hunt

      very interesting, Will.
      You may understand that peak oil and gas is occurring about now yet we use up to around 28% of our petroleum production for agriculture. According to the definition of modern agriculture [which is to convert petroleum into food] it looks ominous that supplies will be in future limited and that will be a drag on agricultural production.
      What is your take on that?

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    14. Will Hunt

      Farmer

      In reply to John Doyle

      There are several things you need to understand. A lot of the stuff you read about farming comes from Nthn Hemisphere. For instance, nearly 40% of the energy used in growing crops in UK is used in crop drying.
      We have a particularly effective solar drying system in Australia called the sun. I have never used a crop drier. Most Australian farmers have never seen one.
      Another 40% of energy is used in making Urea fertilizer I believe by sqirting natural gas up a vertical pipe. The gas collects…

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    15. John Doyle

      architect

      In reply to Will Hunt

      Thanks for the clarification. Yes I know we mostly generalize on US or European data, and that our farming sector is pretty high in efficiency by comparison.
      However I also do not support the vegan attitude. We need animals to convert pasture into food. If we don't have animals we take pasture out of the food chain to a large extent. How clever is that?
      Allan Savory shows how we can use animals to conserve pasture sustainably. We can do what he suggests and already do because of electric fencing.
      I worry we are heading for a perfect storm. Declining soil fertility [if you believe the 2006 Cornell Uni study which forecasts 30% of cultivated soils will be unuseable by 2050] declining petroleum availability, increased demand due to rising affluence and loss of nutritional value in food due to huge acreages of Canola, soy and white corn crops mostly nutritionally worthless.
      "Interesting times" afoot, as the chinese proverb has it!

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    16. Will Hunt

      Farmer

      In reply to John Doyle

      Allan Savory is an inspiration, isn't he? So quietly spoken and authoritative with run on the board to back him up, and its not rocket science- And yet, it took him years to work it out!
      http://www.youtube.com/watch?v=vpTHi7O66pI
      You often hear about 'factory farming', but to my way of thinking 'factory farming' is more to do with countless thousands of acres of force fed soul-less monoculture than a shed full of chooks
      Thanks for your time John, a pleasure to converse with someone without an agenda

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    17. John Doyle

      architect

      In reply to Will Hunt

      I can say same re you, Will.
      I am not a farmer, but my mum was on the land [dad was a solicitor] and my cousin runs a farm in New England, mostly grazing.

      Did you know Allan Savory is coming to Australia in August?
      Call Trevor on 02 6373 7763.

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    18. Will Hunt

      Farmer

      In reply to John Doyle

      Hi John,
      Just found out that there is a new trendy name for the way we farm, it's called 'Polyculture'
      Yeah. How about that.
      Thought I'd let you know
      Surprised me too

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    19. John Doyle

      architect

      In reply to Will Hunt

      Not really a surprise, Will. It's a type on the continuum between permaculture and monoculture.
      Where is your farm?

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    20. John Doyle

      architect

      In reply to Will Hunt

      Impressive Will [Bill]! My son is Will, so I prefer that. He's a builder.
      Who buys your mutton? I din't know people were still doing that. All we hear of is lamb now, but there was a lot of mutton around in the 40's and 50's when I was a boy.
      Durum wheat too. I understand australia's crop is a premium one and the Italians try to get all of it. I lived there for 11 years too.
      Thank you.

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    21. Will Hunt

      Farmer

      In reply to John Doyle

      Hi John,
      The name of the breed is 'South African Mutton merino' but we sell the wether portion as lambs to Tatiara meat, which is about 8 km from our front gate. They are one of Australias biggest lamb exporters
      The ewe portion get sold as hoggetts to prime lamb breeders.
      We also have an Oat mill in Bordertown which uses 70-80,000 tonnes pa, and there is a mill which buys beans at Keith which is 60km up the road.
      SanRemo in Adelaide have been buying all our durum for years
      Keeps our food kms down as well, so thats a plus.
      A lot of Australian farmers don't have the marketing options that we have, so we're lucky I guess.

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  2. Bob Phelps

    Director at Gene Ethics

    Hello Sharon:

    Please provide a primary reference and data for the claim that: "there has been an 80% reduction in the use of chemical pesticides previously required to control bollworms."

    Has the amount of pesticide used to control other insects not susceptible to death from exposure to Bt toxins - such as mirids, aphids and thrips - increased since Bt cotton was introduced?

    Is fusarium wilt more common in GM than non-GM cotton crops? And, if so, which chemicals are used to control fusarium and in what quantities?

    What is the evidence that Bt cotton is: 1. more or less effective than the topical spraying of Bt bacteria to control caterpillars; and 2. more or less susceptible to insect resistance than topically applied Bt bacteria?

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  3. Janet Grogan

    Communications provider

    Hello Sharon, You say that there has been 80% reduction in bollworm chemical usage but I was wondering how you measure the toxin that the plant itself produces, and how it compares to this saving? The production of a toxin in every cell of the plant for the life (and beyond) of that plant must add up to a lot.The leaching of this into the soil while the plant is alive, and during decomposition into the soil, and waterways must be something that has been taken into account when comparing cotton crops before and after GM techniques.Has this ever been done?

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