INFLUENCE OF SOIL TEXTURE, SOIL-MOISTURE, ORGANIC COVER, AND WEEDS ON OVIPOSITION PREFERENCE OF SOUTHERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE)

Oviposition preferences of the southern corn rootworm, Diabrotica undecimpunctata howardi Barber, were investigated in greenhouse experiments where abiotic and biotic parameters were manipulated. Southern corn rootworm oviposition distance from corn seedlings was quantified. Four soil moistures, four soil textures, and the presence of weeds were examined in caged greenhouse experiments for their effect on southern corn rootworm oviposition preference. Additional experiments were conducted to elucidate southern corn rootworm oviposition preference for corn seedlings in the presence of broadleaf weeds, grass weeds, a wheat straw cover, or bare soil in large-cage experiments in the greenhouse. Southern corn rootworm adults oviposited >90% of their eggs within 3 cm of a corn stem with <1% oviposited 10-15 cm from the plant. Soil moisture and texture significantly affected oviposition preference. Moist or wet soil and dark soils (moderately high in organic matter and clay) were preferred for oviposition. Significant interactions occurred between these two variables. The presence of weeds significantly increased the number of eggs oviposited and influenced the oviposition preference for particular soil moistures and textures. Southern corn rootworm adults preferred to feed on and oviposit in areas that contained broadleaf weeds compared with grass weeds, wheatstraw, or bare soil. The presence of a wheatstraw cover was significantly (P < 0.05) preferred to bare soil. We discuss how this study elucidates a number of seemingly contradictory field observations of southern corn rootworm infestations. © 1990 Entomological Society of America.