OVIPOSITION SITE SELECTION OF THE NORTHERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE)

Oviposition habits of adult Diabrotica barberi Smith & Lawrence were studied in relation to varying sources of vegetative cover during 1986 and 1987 at three locations in east central South Dakota. Treatments included the following: com, Zea mays L.; soybeans, Glycine max L.; simulated volunteer oats, Avena sativa L.; a mixture of green and yellow foxtails, Setaria viridis (L.) Beauvois and S. lutescens (Weigel) Hubb.; common lambsquarters, Chenopodium album L.; redroot pigweed, Amaranthus retroflexus L.; and Pennsylvania smartweed, Polygonum pennsylvanicum L. Sticky trap data indicated the presence of high beetle populations in plot areas during both years. Totals of 3,447, 8,758, and 14,178 D. barberi were captured at Aurora, Rutland, and Wentworth, respectively. Typically, greater numbers of adults were captured in the com plots; however, high numbers were also present within all other treatments. Soil sampling conducted before D. barberi oviposition produced overall means of 1.81, 0.23, and 0.06 eggs per 0.47-liter sample at Rutland, Aurora, and Wentworth, respectively, and indicated that negligible numbers of diapausal eggs were present. Egg recovery after oviposition was significantly (P < 0.01) higher in com plots than in noncorn plots, thus indicating that cornfields provide the preferred site for D. barberi oviposition.