(Beyond Pesticides, January 3, 2014) A recent study on the European corn borer (ECB), a major corn pest, finds no significant difference in yield between genetically engineered (GE)Bt (ECB-resistant) corn and non-GE corn in the Northeast, where pest pressure has decreased. Considering the high cost of GE corn, researchers determine that farmers will see no benefits in terms of profit. The study, published in the journal Pest Management Science, examines the damage that ECBs cause to crops, comparing corn genetically engineered to express the insecticidal toxin Bacillus Thuringiensis (Bt) with non-Bt crops at 29 sites around Pennsylvania over three years.
The study concludes that although Bt corn hybrids reduced ECB damage in comparison to non-Bt crops, they found no difference in yields, explaining that because of higher seed costs they also “rarely improved profits.” Although researchers attribute the decline in ECB population to the adoption of Bt corn, the study does not address long-term insect resistance which can develop in fields after the introduction of GE crops and lead to an increased use in pesticides.
“With less ECB damage around, non-Bt hybrids in our tests yielded just as well as Bt hybrids, so the decline in ECB populations provides an opportunity for growers to generate greater profits by planting high-yielding non-Bt seed, which is much cheaper than Bt seed,” said Eric Bohnenblust, graduate student and co-author of the study, to Penn State News. “Planting more non-Bt corn will [also] reduce the potential for ECB to develop resistance to Bt toxins as corn rootworms have done in about a dozen states so far.”
The researchers suggest that farmers should consider planting non-Bt corn as a cost-cutting measure,and conclude that “Bt hybrids remain valuable control options.” However, there is mounting evidence demonstrating insect resistance, crop contamination, and potential adverse impacts of GE crops to human health and the environment.
Indeed, in 2011 entomologists at Iowa State University published a study verifying the first field-evolved resistance of another corn pest, corn rootworm, to a Bt toxin. The study found the western rootworm’s ability to adapt was strongest in fields where Bt corn was planted for three consecutive years and suggested that insufficient planting of refuges may have contributed to the resistance. This study was cited by a group of 22 prominent entomologists who submitted formal comments to the EPA, identifying significant flaws in current practices for managing insect resistance to Bt corn and cautioning that failure to implement alternative measures would result in all forms of Bt losing its effectiveness. Similarly, a 2013 study by University of Illinois researchers found corn rootworm to be resistant to GE Bt corn within two of Illinois’ counties, causing severe damage to those crops.
The European corn borer causes severe damage to the corn in the larval stage. As larvae emerge from overwintering, they feed and tunnel within the tassel, ear, and stem forming cavities within the crop. This boring damage weakens the plant, diminishing yields as the plant becomes unable to transport water and nutrients through the damaged stalk. Previous research in Pennsylvania suggests that ECB was responsible for about a 5.5% yearly yield reduction in field corn. Extensive yield losses from reduced leaf area, broken stalked, dropped years, and stalk rot, caused by ECB and corn rootroom led to widespread use of Bt-corn. Research here suggests however, that these yield gains are no longer being made, and farmers should consider planting non-Bt corn.
Genetically engineered crops not only facilitate insect resistance but also threaten the sustainability of organic agriculture. There has long been a concern that EPA’s allowance of plant incorporated protectants (PIPs) with Bt would lead to the failure of a biological tool used in organic farming systems as an alternative to highly toxic synthetic inputs. Organic farmers have expressed concern since the introduction of PIPs in 2003 that the overuse of Bt, which is inevitable when Bt is genetically engineered into every cell of a plant, will lead to insect resistance and leave many farmers without an important tool of organic agriculture.
Organic agriculture is the last sustainable refuge from genetically engineered crops. It represents an ecologically-based management system that prioritizes cultural, biological, and mechanical production practices and natural inputs by strengthening on-farm resources, such as soil fertility, pasture and biodiversity. For more reasons to support organic agriculture, visit Beyond Pesticides’ Why Organic page.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.