Growing genetically modified insect-resistant corn in the United States has dramatically reduced insecticide use and created a “halo effect” that also benefits farmers raising non-GM and organic crops, new research shows.
This finding, published by University of Maryland researchers in the prestigious peer-reviewed journal Proceedings of the National Academy of Sciences, effectively shreds the conventional anti-GMO narrative that GM crops result in more pesticide use and present a threat to organic growers.
In fact, the reverse seems to be the case. The researchers examined the populations of two insect pests — the European corn borer and corn earworm —that attack vegetables such as green beans and peppers as well as field corn, before and after the widespread adoption of genetically modified Bt corn in 1996.
The scientists charted a steep decline in these insect pest populations that corresponded closely with the widespread adoption of Bt corn. This suggested that an area-wide suppression of pest populations, termed the “halo effect,” was benefiting vegetable growers across three mid-Atlantic US states.
This GMO halo effect in turn allowed vegetable growers to dramatically reduce the insecticide sprays they had previously relied on to prevent damage to their crops. For example, the pest pressure declines in New Jersey allowed farmers to report insecticide use reductions of 79 percent in sweet corn and 85 percent in peppers between 1992 and 2016.
“This is the first paper published showing offsite benefits to other host plants for a pest like the corn borer, which is a significant pest for many other crops like green beans and peppers,” said lead author Dr. Galen Dively, professor emeritus and integrated pest management consultant in the Department of Entomology at the University of Maryland. “We are seeing really more than 90 percent suppression of the European corn borer population in our area for these crops, which is incredible.”
Organic vegetable growers, who forswear the use of synthetic pesticides and whose crops are therefore particularly vulnerable to insect damage, might have been particular beneficiaries of the adoption of genetically modified Bt crops, the researchers suggest. The protective benefit of GMO adoption for organic and conventional crops has been suggested before, but this is the first time it has been confirmed by extensive field research.
Bt crops may also be environmentally beneficial by promoting biocontrol services through the maintenance of pest predator populations, such as ladybirds, lacewings and spiders, an important component of integrated pest management. Insecticide sprays might otherwise have killed these “good” insects, which prey on pests.
Dively concluded: “This study ultimately shows the importance of evaluating GE crops beyond the field that is being planted. These products and the new advances coming down the pipeline have the potential to suppress major pest populations just like Bt corn has. This is just the beginning, and we need to be quantifying these effects. I am excited by these results and encouraged for future work.”