Impact of Corn Planting Date on the Population Dynamics of Corn Rootworms (Coleoptera: Chrysomelidae)

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Abstract
Populations of corn rootworms (Diabrotica virgifera virgifera LeConte and D. barberi Smith and Lawrence) were monitored weekly from egg hatch through adult emergence on four and three corn planting dates in 1981 and 1982, respectively. Planting dates ranged from late April to early June. Significantly fewer larvae and adults were collected from corn planted in June. In addition, the date corresponding to 50 and 90% occurrence of third-stage larvae, pupae, and adults was significantly delayed by later planting. Numbers and the seasonal occurrence of first instars were not 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 earlyhatching larvae.