EFFECT OF POPULATION DENSITY OF IMMATURES ON SURVIVAL AND DEVELOPMENT OF THE WESTERN CORN ROOTWORM (COLEOPTERA: CHRYSOMELIDAE)

Abstract
A field study with controlled infestations of eggs of the western corn rootworm, Diabrotica virgifera virgifera LeConte, was conducted over a four-year period. The percentage of insects surviving to adulthood was significantly reduced at an infestation of 2400 eggs per 0.3 m of row compared with rates of 300, 600, and 1200 eggs per 0.3 m of row. Survival to adulthood varied among years suggesting that biotic or abiotic factors in the soil, possibly soil moisture, may have influenced survival. The Julian date associated with mean adult emergence was significantly later at the 2400 egg infestation rate than at lower rates. These results suggest that immature survival is reduced and developmental time increased at high population densities.