Assessing risk to rotated corn in Iowa and effects of soybean varieties on Diabrotica virgifera virgifera LeConte

The western corn rootworm Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) is a significant insect pest of corn in North America. Corn growers traditionally use crop rotation as an inexpensive and effective tool to prevent yield loss from Diabrotica spp. However, in regions of the Midwest, D. v. virgifera has evolved resistance to crop rotation by laying eggs in soybean fields. We investigated whether varieties of soybeans with resistance to soybean aphid Aphis glycines Matsumura (Homoptera: Aphididae) could affect survival and fecundity of D. v. virgifera. Experiments were run with plants grown in the greenhouse and field. Soybeans tested with resistance to A. glycines were Michigan and Rag varieties, and we included a non-Rag near isoline as an experimental control. Newly emerging female D. v. virgifera were mated for 10 days then randomly assigned to treatments of either alternating diet of corn and soybean, alternating diet of corn and no food, or diet of corn alone. Every two days individual survival, oviposition, and feeding were recorded. Individuals fed corn ear continuously had significantly greater egg production then those alternated between corn and some of the soybean varieties. There were no statistical differences between the three soybean varieties for survival, egg production, or soybean leaf area consumed for both greenhouse and field trials.