Producers in east central Illinois have been plagued since the mid-1990s with a new strain of western corn rootworm, Diabrotica virgifera virgifera LeConte, that lays eggs in soybean, nullifying the value of crop rotation as a pest management tool. During the summer of 2000, a 32-hectare experiment was planted at the University of Illinois South Farms, Champaign-Urbana, Illinois. The objective of our study was to create phenological differences in maize and soybean development and evaluate the potential effect of these treatments on western corn rootworm oviposition. We used a randomized complete block design with eight treatments that consisted of four varieties of soybean, Glycine max, each with a different maturity date, and two maize, Zea mays L., hybrids, each planted at an early and later date. Densities of western corn rootworm adults were monitored in all treatments with cucurbitacin-baited vial traps. Densities of egg were assessed by taking soil samples after all treatments were harvested. A smaller, control study (6.7 ha) with similar treatments was located in northwestern Illinois (near Monmouth, Warren County) where this new strain of western corn rootworm has not been detected. In Champaign-Urbana, numbers of adults captured in vial traps in soybean plots increased significantly after corn developed past the R2 stage. Soil samples showed that significantly more eggs were deposited in soybean and late-planted corn (10.8-5.45 eggs/ pint) than in early-planted corn (4.3 eggs/ pint). Conversely, in Monmouth, we collected significantly more adults in corn than in soybean, and significantly more eggs were deposited in corn (~9.5-6.8 eggs/ pint) than in soybean (0.0 eggs/ pint). Crop rotation has played an important role in the selection pressure that has caused this shift in egg-laying behavior of the western corn rootworm. Our study suggests that crop phenology also plays a role, at least in east- central Illinois.
Species 1: Coleoptera Chrysomelidae Diabrotica virgifera virgifera Leconte (western corn rootworm)
Keywords: oviposition, crop phenology
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA