SOIL-MOISTURE AND SURVIVAL OF WESTERN CORN-ROOTWORM LARVAE IN-FIELD PLOTS

During the 1993 growing season, extensive rainfall fell upon field plo ts that had been manually infested with western corn rootworm (Diabrot ica virgifera virgifera LeConte) eggs. The topography of the plot area and extensive precipitation combined to saturate the topsoil in a por tion of the field during egg hatch. In this area, larval feeding (root -damage ratings) and survival to adulthood (beetle emergence) were sig nificantly reduced when compared with the portion of the field that ha d unsaturated soil. Root pull resistance was also lower in the saturat ed portion of the field, suggesting that the soil moisture conditions that reduced western corn rootworm populations also inhibited root gro wth. These findings suggest that, while water saturated soil at specif ic times of the life cycle may reduce corn rootworm populations, the m agnitude and duration of this treatment needed to achieve this reducti on may adversely affect plant growth and development.