Patterns of cross pollination between Bt and non-Bt corn and effects on Helicoverpa zea (Lepidoptera: Noctuidae) in blended refuges of short-stature corn and tall corn.

Short-stature corn became available to farmers in the United States in 2025. Advantages of short-stature corn over taller corn hybrids include lodging resistance, convenient sprayer access, and the potential for higher planting density. Corn earworm, Helicoverpa zea (Boddie), is an important insect pest of corn and other crops throughout the United States, but little is known about how corn earworm interacts with short-stature corn. Genetically modified corn containing genes from the bacterium Bacillus thuringiensis Berliner (Bt) produce toxins that, once ingested, kill insect pests. Blended refuges, in which non-Bt and Bt seeds are planted together within a field, are a method for delaying insect resistance to Bt toxins. Past studies indicate that pollination between Bt and non-Bt corn in blended refuges has consequences for corn earworm resistance management. Our field study used plots of Bt corn, non-Bt corn, and blended refuges of either short-stature corn or tall corn and a Bt-susceptible laboratory colony of corn earworm. We measured survival, kernel injury, and development of corn earworm larvae in these plots and cross pollination between corn plants in blended refuges. In general, Bt plants had fewer larvae and suffered less injury than non-Bt plants, regardless of whether plants were grown in a pure stand or a blended refuge. In our preliminary study, results for short-stature corn mostly resembled those for tall corn. However, more research is necessary to determine if current resistance management recommendations for corn earworm in tall corn are applicable for short-stature corn.