The European corn borer (Ostrinia nubilalis), shown here in its larval stage, feeds on more than just corn. A new study of 40 years’ worth of data from the mid-Atlantic region of the United States finds that widespread adoption of insect-resistant Bt corn has reduced pest damage and the need for insecticide applications in offsite, non-Bt crops such as pepper, green beans, and sweet corn, as well. (Photo credit: Phil Sloderbeck, Kansas State University, Bugwood.org)

Farmers that plant insect-resistant corn aren’t just helping their own harvests. As it turns out, other growers nearby benefit, as well—even if they’re growing other crops that aren’t pest-resistant themselves.

In a new study published in Proceedings of the National Academy of Sciences, a team led by researchers at the University of Maryland (UMD) has shown that the adoption of Bt corn—genetically engineered to express insecticidal proteins from the bacteria Bacillus thuringiensis (Bt)—over the past 20 years can be linked to measurable benefits to non-Bt crops such as pepper, green beans, and sweet corn. Growers of those other vegetables have reported less pest damage to their crops and less usage of chemical insecticides in that time.

Galen Dively, Ph.D., professor emeritus and integrated pest management consultant in the UMD Department of Entomology, and P. Dilip Venugopal, Ph.D., UMD research associate—along with colleagues at the University of Delaware, Rutgers University, Virginia Tech, and University of Minnesota—analyzed data from the mid-Atlantic region of the United States covering a 40-year period, 1976-2016, to learn how non-Bt crops were affected by major pests such as the European corn borer (Ostrinia nubilalis) and the corn earworm (Helicoverpa zea). They found that, in the latter half of that span, widespread Bt corn adoption was associated with region-wide declines in pests and benefits from the pest reduction extending beyond the borders of corn fields.

“We are seeing really more than 90 percent suppression of the corn borer population in our area for any crop, which is incredible,” Dively says in a report from the UMD College of Agriculture and Natural Sciences.

For instance, European corn borer damage in peppers in the mid-Atlantic declined from an average of 35 percent per year in the span 1980 to 1995 to an average of 8 percent in the years since Bt corn introduction in 1996, a 78 percent decrease. Similarly, sweet corn damage from the European corn borer declined from an average of 50 percent per year in the period 1984 to 1995 to 15 percent per year after 1996, a 70 percent decrease. These damage reductions are directly linked to the extent of Bt field corn adoption.

Further research could begin to calculate the benefits of Bt corn adoption in terms of the potential losses avoided by reduced pest prevalence in offsite crops, Venugopal notes. He also says he is curious about the role that offsite non-Bt crops play as “unstructured refuges” for O. nubilalis and H. zea, which may aid in slowing the development of resistance to Bt in the pests.

“The next steps would to be quantify the millions and millions of dollars in economic benefits we see here in a very concrete way, to show money and time saved on spraying and pest management, crop damage reduction, as well as consideration of the environmental benefits,” he says. “The important thing here, however, is to think of Bt corn as one of many tools in an integrated pest management tool box.”