IMPACT OF CORN PLANTING DATE ON THE POPULATION-DYNAMICS OF CORN ROOTWORMS (COLEOPTERA, CHRYSOMELIDAE)

Populations of corn rootworms (D. v. virgifera LeConte and D. barkeri Smith and Lawrence) were monitored weekly from egg hatch through adult emergence on 4 and 3 corn planting dates in 1981 and 1982, respectively [Indiana, USA]. Planting dates ranged from late April-early June. Significantly fewer larvae and adults were collected from corn planted in June. The date corresponding to 50 and 90% occurrence of 3rd-stage larvae, pupae, and adults was significantly affected by planting date. The effects of delayed planting on the population dynamics of corn rootworms presumably relates to reduced availability of corn roots resulting in mortality of early-hatching larvae.