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Corn Rootworm Resistance to Toxins in GE Crops, Says EPA

(Beyond Pesticides, January 25, 2013) The U.S. Environmental Protection Agency (EPA) has concluded that corn rootworm is now resistant to genetically engineered corn infused with a toxin derived from Bacillus thuringiensis, or Bt, in certain parts of the Corn Belt, casting doubt on the future viability of GE corn. The conclusion of the Insect Resistance Management (IRM) Team is based on several years of data indicating that the Cry3Bb1 protein strain of Bt is ineffective at controlling corn rootworm.

The press release on January 17 states: “The EPA IRM Team has concluded that corn rootworm may not be completely controlled by Cry3Bb1 in certain parts of the Corn Belt. While ‘confirmed resistance’ as defined in registration documents has not been met, given the nature of the data, the manufacturer, Monsanto, has agreed to several actions and changes related to the registration of Cry3Bb1 products to address these matters.”

Originally marketed by Monsanto in 2003, the protein Cry3Bb1 is designed to destroy the gut of the western corn rootworm. The rootworm has historically devastated corn fields, causing greatest damage in chemical-intensive agriculture during its larval stage by feeding upon the plant’s roots, inhibiting the plant’s ability to absorb moisture and nutrients while opening a pathway for attack from soil-borne pathogens. Monsanto genetically engineered corn plants to produce Cry3Bb1 derived from a gene in Bt in order to control these insects.

Before the introduction of insecticide-producing corn plants, Midwest farmers typically tried to keep pests like the rootworm in check by changing what they grew in a field each year, often rotating between corn and soybeans. That way, the offspring of corn-loving insects would starve the next year. As proponents of genetically engineered crops claimed they would reduce pesticide use and increase drought resistance, many large scale farms have shifted their practices. In fact, studies have shown since the widespread adoption of GE in the 1990s that, to the contrary, pesticide use increases with GE crops. Insect resistance, weed resistance, and cross contamination of other crops have also been documented. Research on corn rootworm by entomologists at Iowa State University, published in 2011, verified the first field-evolved resistance of corn rootworm to a Bt toxin. The researchers documented resistance to the Bt toxin Cry3Bb1, which has been inserted into nearly one third of the corn planted in the U.S. Additionally, data released in February of 2012 shows that more than 40% of American farmers are neglecting to comply with mandatory management practices for Bt planting that are designed to minimize the risk of insect resistance.

Not only does insect resistance to Bt and its strains raise concerns about their efficacy, but the continued use of Cry3Bb1 poses serious threats to public and environmental health. Indeed, one recent study, led by scientists at the University of Caen in France, demonstrates that at very high doses Bt is toxic to human cells, and glyphosate in the formulated product Roundup, which is used in high volume with GE herbicide- tolerant corn, damages human cells, even in extremely low doses. In their investigations, the researchers examined several products, including the Cry1Ab and Cry1Ac, other Bt toxins developed by Monsanto for inclusion in GE crops, as well as the glyphosate formulation Roundup. The study supports research published in the May 2011 edition of the journal Reproductive Toxicology which found that pregnant women and their fetuses were contaminated with pesticides and metabolites of the herbicide gluphosinate and the Cry1Ab protein.

In addition, Bt impacts on non-target organisms as well as environmental contamination cannot be dismissed. A study conducted by Hellmich et al. (2001) investigated the sensitivity of the monarch butterfly to Cry proteins and found that the first instars (stage between molts) were sensitive to Cry1Ab and Cry1Ac proteins, with Cry1Ab having the most impact on the species. Kim et al. (2008) also found that Cry1Ac lead to decreased survival rates and body weights among the non-target larvae of silkworms, Bomyx mori. These studies support the notion that non-target organisms are indeed at risk from exposure to GE crops on agricultural fields and the environment.

Beyond Pesticides believes that whether it is the incorporation into food crops of genes from a natural bacterium (Bt) or the development of a herbicide-resistant crop, the GE approach to agriculture and pest management is short sighted and dangerous. There are serious public health and pest resistance problems associated with GE crops. The failure of the EPA to properly exercise its authority to regulate the plant incorporated protected used in Bt corn products is unacceptable. EPA’s faulty determination of refuge requirements and registrants’ failed oversight of the corresponding compliance practices have contributed to the confirmed in-field emergence of western corn rootworm resistance to the Cry3Bb1 toxin. Confirmed in-field resistance combined with EPA’s outright acknowledgment of corn rootworm resistance to the Cry3Bb1 toxin makes it clear that the refuge requirements and compliance provisions underlying all Bt corn product registrations urgently need reconsideration. Failure or further delay on EPA’s part to implement refuge requirements and compliance activities that seek to preserve the efficacy of Bt corn products and extend their utility in the field will result in undue adverse environmental, human health and economic consequences, as well as undermine the use of Bt as a biological pest management tool in organic production.

For more news and information on GE crops, see Beyond Pesticides’ genetic engineering page, or for information on alternatives to GE crops and chemical dependence, visit our organic food and farming page.

Genetic engineering, food as well as the effects of pesticides on human health will be topics of discussion at the 31st National Pesticide Forum on April 5-6, 2013 at University of New Mexico in Albuquerque, NM. Conference speakers include Joel Forman, MD, author of the recent report “Organic Foods: Health and Environmental Advantages and Disadvantages,” and public interest attorney, activist and author Andrew Kimbrell, executive director of the Center for Food Safety, and many more.

Source: US Environmental Protection Agency

All unattributed positions and opinions in this piece are those of Beyond Pesticides.


One Response to “Corn Rootworm Resistance to Toxins in GE Crops, Says EPA”

  1. 1
    Paul Says:

    What a shame to damage such a fine bio control like btk. These results had been predicted based on our prior experience with resistance to DDT and other pesticides. Praise God for our capacity to learn, unite, seek justice and advance our civilization. Thank you to you people that care and operate this wonderful organization.

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