EFFECTS OF SOIL-MOISTURE, TEXTURE, AND RATE OF SOIL DRYING ON EGG AND LARVAL SURVIVAL OF THE SOUTHERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE)

Greenhouse studies were conducted to determine the effects of four soil textures and four soil drying periods on southern corn rootworm, Diabrotica undecimpunctata howardi Barber, egg and larval survival and maturation. Soil drying intervals had the most detrimental effect on survival. After 4 d of soil drying (no water added to pots), only 20% of larvae survived to pupation. Low clay or organic matter and low levels of soil moisture were not conducive to survival of southern corn rootworm. The interaction of soil texture and soil drying indicates that at 4 d of soil drying, larval survival decreased (70%) in all soils, except dark-textured soils (35% decrease) compared with 2 d of soil drying. Low levels of soil moisture slowed developmental time of larvae. Eggs and first instars were the stages most negatively affected by moisture stress and different soil textures. However, in quartz-sand, the more mobile stages had low survival, probably because of cuticle abrasion from soil particles. The results of these experiments demonstrate the importance of considering the effects of rapidly drying soil on survival of southern corn rootworm and not simply the percentage of soil moisture at any one time. © 1990 Entomological Society of America.