A Descriptive Study of the Population Dynamics of Adult Diabrotica Virgifera Virgifera (Coleoptera: Chrysomelidae) in Artificially Infested Corn Fields

Abstract

The influence of corn plant phenology on the dynamics of adult western corn rootworm, Diabrotica virgifera virgifera, populations was studied during 1988 and 1989 in corn fields artificially infested with eggs. Fifty percent of adult emergence from the soil occurred by day 194 in 1988 and day 203 in 1989. In both years, adult emergence was synchronized with corn flowering, eggs were recovered in soil samples approximately four days after reproductive females were first observed in the population, and oviposition was essentially compLete about 25 days after it began. The number of reproductive female beetle-days accumulating per m2 was similar in both years. Approximately two times as many eggs were laid in 1988 (1239 eggs/m2) as in 1989 (590 eggs/m2). The difference in egg density may have been caused by differences among years in the temporal synchrony of reproductive beetles with flowering corn. Daily survival rates of adults were high while corn was flowering; exhibited a gradual decline during grain filling; and decreased rapidly during the grain drying stage.