Farmers still Suffering from Bt Resistant Rootworms

Crop rotation strategies not alleviating Bt resistance in Illinois Dr Eva Sirinathsinghji

Excerpt from Water Carnival - the images of organisms discovered in Mae-Wan Ho's laboratory within a quantum jazz soundscape. Download the full video from the online store.

New evidence from two Illinois farms shows that even integrated pest management strategies such as crop rotation are unable to stave off the spread of Bt pest resistance to genetically modified (GM) Bt corn [1]. After planting Monsanto’s VT Triple PRO RIB corn containing the insecticidal Cry3Bb1 toxin for the first time, the farmers from Livingston and Kankakee counties saw severe damage to their corn as well as soybeans grown in adjacent fields. They went on to contact entomologists Dr Joe Spencer and Dr Michael Gray from the University of Illinois to come and analyse the damage.

The first official evidence of resistance to Bt toxins in the field was published in 2010 [2] (see [3] Bt Rootworm Spreads, SiS 52). Since then, GM proponents have claimed that a lack of compliance by farmers to include a refuge area of non-GM corn, as well as dropping traditional pest management strategies of crop rotation were the underlying reasons for the development of such rapid resistance to Monsanto’s Bt crops. However, in both the present cases, the farmers have stuck to crop rotation strategies only to find a complete failure of Monsanto’s GM technology to do its job. The crops are suffering from large numbers of pests (Figure 1), severe root pruning (Figure 2) and damage (Figure 3) as well as lodging of the plants (Figure 4). Pest numbers were reportedly comparable to levels seen in the late 1990s and early 2000s. Further lab tests are planned to confirm genetic Cry3Bb1 resistance in the pests themselves. The scientists are now warning farmers that they may face serious challenges in protecting their crops.

The process of crop rotation is meant to delay the time needed by pests to adapt to the toxin and gain resistance. Monsanto states that every grower of their Bt crops must comply with licensing agreements that include an Integrated Pest Management plan with crop rotation, the planting of non-GM refuge areas, as well as selecting appropriate cultivars among other things [4]. The company claims that growers of its crops “have found them to be highly compatible with their goals of integrated pest management (IPM) and sustainable agriculture”. However, the refuge strategy depends on high expression of the Bt toxins, but as mentioned earlier, this is not the case. Also, Monsanto managed to successfully persuade the US Environmental Protection Agency (EPA) to reduce the size of the non-GM refuge to 10 % instead of 50 % [3]. Now, on top of all that, the crop rotation has been shown insufficient to control the spread of Bt resistance in target pests. Monsanto simply cannot keep claiming that their crops work.

Figure 1 Corn rootworm infestation of Monsanto’s VT Triple PRO RIB Bt corn [1]

Figure 2 Pruning of roots of Monsanto’s VT Triple PRO RIB Bt corn plants by rootworm infestation [1]

Figure 3 Rootworm damage Monsanto’s VT Triple PRO RIB Bt corn [1]

Figure 4 Lodging of Monsanto’s VT Triple PRO RIB Bt corn plants resulting from corn rootworm damage [1]

The evolution of pesticide resistance pests is all too predictable to anyone who understands the process of evolution or farming. Even Monsanto admits that “resistance is natural and expected, so measures to delay resistance are important” [5]. All the more so when we learn that some of Monsanto’s Bt crops express the toxin at insufficient levels to prevent the development of non-recessive resistance. Non-recessive resistance is when the resistance gene is dominant and therefore only requiring one copy (heterozygosity) of the gene to be resistant to the toxin. Recessive resistance on the other hand would require two copies of the resistance gene to make the pest resistant and therefore, resistance would spread more slowly. Agritech companies have seized the opportunity for easy profit following mass cultivation of Bt crops; American Vanguard, for example, bought a number of insecticide companies and technologies with the expectation that pesticide demand would rise after an temporary dip when Bt crops were initially commercialised [6]. Contrary to what GM corporations and proponents claim, overall pesticide use has risen as a direct result of GM crop cultivation, mainly attributable to massive rises in glyphosate use alongside glyphosate-tolerant crops. Pesticide use has gone down since the introduction of Bt crops, but is rising again and if Bt crops were counted as “pesticides applied”, and there is a strong case to do so, then insecticide use never went down at all (see [7] Study Confirms GM Crops lead to increased Pesticide Use, SiS 56). The spread of resistance will only lead to further increases in toxic chemicals being applied to our food, leaving consumers exposed to double doses of toxic insecticides. Chemical companies have seen profits rise, with The Newport Beach, Calif. reporting its soil-insecticide revenue jumped 50% in 2012. Its insecticide sales rose 41% in the first quarter of 2012 to $79 million, with gains driven by corn insecticide [6].

Not only are the Bt crops unable to do the two things they were meant to do - protecting crops from pests and reducing pesticide use - they are also having detrimental effects on non-target pests, and causing the infestation of crops with secondary pests even when the Bt crop is still able to kill the target pests. Further, Bt crops have been shown to cause health problems to those cultivating them as well as those consuming them. For a review on the health and environmental risks of Bt crops see [8] Bt Crops Failures and Hazards, SiS 53 and [9] Ban GMOs Now.

Article first published 16/09/13

References

Severe Corn Rootworm Injury to Bt Hybrids in First-Year Corn Confirmed. The Bulletin http://bulletin.ipm.illinois.edu/?p=1629 10th August 2013 Gassmann AJ, Petzold-Maxwell JL, Keweshan RS, Dunbar MW. Field-evolved resistance to Bt maize by Western corn rootworm.PLoS One2010, 6, e22629 Sirinathsinghji E. Bt Resistant Rootworm Spreads.Science in Society 52, 34-36, 2012 Monsanto.com http://www.monsanto.com/products/Pages/insect-resistance-management.aspx, accessed 10th September 2013 Monsanto India,accessed 10th September 2013 http://www.monsantoindia.com/monsanto/layout/pressreleases/mmb_pressrelease.asp Chemical creep: Farmers return to pesticides as GMO corn loses bug resistance. Grist.org http://grist.org/news/chemical-creep-farmers-return-to-pesticides-as-gmo-corn-loses-bug-resistance/, accessed 10th September 2013 Sirinathsinghji E. Study Confirms GM crops lead to increased Pesticide Use. Science in Society 56, 8-10, 2012 Sirinathsinghji E. Bt Crops Failures & Hazards.Science in Society 53, 44-45, 2012 Ho MW & Sirinathsinghji E. Ban GMOsNow. Health and Environmental Hazards Especially in Light of the New Genetics. I-SIS Special Report, 2013.https://www.i-sis.org.uk/Ban_GMOs_Now.php

Got something to say about this page? Comment on this article Comments may be published. All comments are moderated. Name and email details are required. Anti spam question: