Studies that claim decreases in pesticide use from GM crops are cast into question by a new study on the use of highly toxic neonicotinoid insecticidal seed treatments* in major field crops like corn and soy.

The new study (abstract below) found that neonicotinoid use increased rapidly in the US between 2003 and 2011, with 34−44% of soybeans and 79−100% of corn hectares being treated in 2011. The authors concluded that “insecticide use in field crops has expanded dramatically” with neonicotinoid seed treatments.

Margaret Douglas, graduate student in entomology at Pennsylvania State University and an author of the study, commented, “Previous studies suggested that the percentage of corn acres treated with insecticides decreased during the 2000s, but once we took seed treatments into account we found the opposite pattern. Our results show that application of neonicotinoids to seed of corn and soybeans has driven a major surge in the U.S. cropland treated with insecticides since the mid-2000s.”

The study also found that neonicotinoid seed treatments are being used over a very large area (40 million hectares). In corn and soybeans, Douglas and her co-author John F. Tooker found that neonicotinoid seed treatments are often used as part of “an insurance-based approach to pest management that may be reinforced in the seed market by limited availability of neonicotinoid-free seed”.

Studies claiming insecticide reductions from GM Bt crops mislead

Douglas and Tooker noted that their findings contradict other recent analyses which concluded that insecticides are used today on fewer corn hectares than a decade or two ago. In particular, they stated that studies claiming that Bt crops have decreased insecticide use “do not seem to have considered seed treatments, and so may have overstated reductions in insecticide use”.

As an example of such misleading studies, Douglas and Tooker cited the recent meta-analysis by Klumper and Qaim, which claimed a 37% reduction in chemical pesticide use from GM crops overall and a 42% reduction from Bt insecticidal crops. While Klumper and Qaim’s study was much hyped by the pro-GMO lobby and the recent UK House of Commons Select Committee report on GM crops, its claim is exposed as baseless by Douglas and Tooker’s analysis.

The failure of GMO proponents to consider insecticidal seed treatments when claiming reductions in chemical insecticide use from GM crops was previously highlighted by the authors of GMO Myths and Truths, as well as by Dr Doug Gurian-Sherman. Gurian-Sherman said, “In reality, corn engineered to kill certain insect pests – AKA Bt corn – has mainly resulted in the replacement of one group of chemical insecticides with another.” The new study proves the point with hard data.