(Beyond Pesticides, June 20, 2012) To control a growing insect resistance problem to the widely used biological pesticide Bacillus thuringiensis (Bt) toxin, now genetically engineered into corn, two experts have concluded that the U.S. Environmental Protection Agency (EPA) should double the so-called “refuges” of acreage planted with non-genetically engineered (GE) corn. If the resistance problem continues -exacerbated by these GE pesticide incorporated plants (PIPs), it will eliminate a bio-rational tool often used by organic farmers. The article, â€śDelaying Corn Rootworm Resistance to Bt Corn,â€ť was published in the June 2012 issue of Journal of Economic Entomology. Currently, EPA requires 20 percent of the total acreage to be set aside for refuges for corn producing one Bt protein (CryBb1), and a 5 percent refuge portion for corn that produces two different Bt proteins at the same time. However, earlier this year, inspections found that more than 40% of American farmers who planted certain varieties of the GE corn in 2011 failed inspections to verify compliance with these management practices to prevent insect resistance.
“Most of the corn seed currently produced in the U.S. is transgenic and includes genes for insect control,” said co-author Fred Gould, PhD. “Enlarging refuges will require more seed without corn rootworm control genes. This shift in production will take time, so this process should begin immediately.”
The Western corn rootworm is a potentially devastating pest that does its greatest damage in chemical-intensive agriculture during its larval stage by feeding upon the plantâ€™s roots. Severe feeding inhibits the plantâ€™s ability to absorb moisture and nutrients and opens a pathway for attack from soil-borne pathogens. In 2011, entomologists at Iowa State University published a study verifying 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.
Organic and sustainable agriculture researchers and advocates have long warned that the EPAâ€™s refuge requirements and other preventive measures are inadequate to prevent resistance from rapidly emerging once Bt corn became planted widely. Alternating between Bt and non-Bt varieties and planting varieties that express different Bt toxins are the other primary management tools for delaying the onset of resistance. While slightly more than one million acres of Bt corn were planted in 1996, that number rose to nearly 50 million acres in 2008. Cumulatively, more than 280 million acres of Bt corn and 75 million acres of Bt cotton were planted in the U.S. between 1996 and 2008.
In addition to the problem of resistance to rootworm, recent research shows that the cultivation of Bt corn has negative impacts on beneficial soil life. Before monoculture production became standard practice for many farms, the western rootworm could be effectively managed by crop rotations, including pasture, hay and legume crop components because the insect starves in fields not planted in corn.
For more information on the effects of genetically engineered agriculture, see Beyond Pesticidesâ€™ Program page on Genetic Engineering.
Source: Science Daily
All unattributed positions and opinions in this piece are those of Beyond Pesticides.