Eating a blend of non-toxic corn and genetically modified toxic corn can result in corn earworm pests (Helicoverpa zea) developing longer, more narrow and more tapered wings – shaped like the wings of a fighter jet – that can propel them long distances, increasing the chances the pests will spread resistance to the toxic corn. The findings add to knowledge about how crop diets can influence pest dispersal behavior.

The research suggests that a blend of corn that produces Bt toxin – designed to kill pests – and a small percentage of toxin-free corn can, in just one life-cycle generation, dramatically change the shape of moth wings to make them more aerodynamic, increasing the moth’s capability to fly longer distances.

“Wings from insects eating a blended toxic and non-toxic corn diet were stiffer and more able to travel in higher wind speeds,” said Dominic Reisig, professor and extension specialist of entomology at North Carolina State University and co-corresponding author of a paper describing the research. “These insects are able to get up into the winds and ride them longer distances.”

Researchers at NC State and colleagues wanted to learn if corn earworm pests growing up and eating toxic and non-toxic corn blend diets would have noticeable physical differences from pests that ate purely non-toxic corn or pests that ate purely Bt corn containing either two or three different toxins. The vast majority of corn and cotton grown in the United States contains Bt toxins to control insect pests.

Corn earworms are aptly named: they feed on corn ears. While corn yield loss is not greatly concerning, the pest also enjoys soybean, tomato and cotton plants, making it a ubiquitous pain for farmers.

“Corn is basically like a factory for this insect,” Reisig said. “Corn earworm can overwinter in our state, slowly build up its generations early in the season, and then in July, when corn silks, those moths go in and lay eggs, Almost every single ear of corn produces at least one caterpillar that becomes a moth when it grows up. That’s a lot of bugs. All of that activity also funnels into cotton and soybeans, and that’s why they’re such a big problem.”

The researchers compared wing shapes of moths raised on the blended corn; moths raised exclusively on non-Bt corn; moths raised exclusively on Bt corn containing two different toxins; and moths raised exclusively on Bt corn containing three different toxins.

The results showed that the wings of moths eating the three non-blended corn diets were less aerodynamic and more brittle and deformed, making those moths less apt to travel long distances.

Moreover, moths eating the blended diet showed wing shape changes after just one generation, a striking physical transformation.

“It appears that resistance occurs faster when worms eat these blends, creating individual moths that have multiple resistance mutations,” Reisig said. “This is one more piece of evidence that blending Bt and non-toxic corn pollen is really dangerous for resistance.”

Reisig adds that his program’s work continues on the effects of Bt corn and non-Bt corn diets, including on corn earworm mating success.

K M Mikac, M J Powley, S Barclay, J H Dominguez Davila and D Pezzini co-authored the paper, which appears in Environmental Entomology.

The work received support from a Biotechnology Risk Assessment Grant, project award no. 2018-33522-28741, from the U.S. Department of Agriculture’s National Institute of Food and Agriculture. This research was also supported by a University Global Partnership Network (UGPN) grant (2022-23).

- kulikowski -