Impact of western corn rootworm (Coleoptera : Chrysomelidae) on sweet cornand evaluation of insecticidal and cultural control options

The western corn rootworm, Diabrotica virgifera virgifera LeConte is an imp ortant pest of corn, Zea malls L., causing yield losses from root damage, p lant lodging, and silk feeding. Because little is known about its impact on sweet corn, we conducted research to evaluate the combined effects of inse cticide, planting date, and cultivar on root damage, plant lodging, and yie ld in central New York sweet corn. We also examined the influence of planti ng date and cultivar on the emergence of adult western corn rootworms. The research was conducted in 1994 and again in 1995 by using a split-split plo t experimental design with insecticide as main plot, planting date as subpl ot, and cultivar as sub-subplot. The effect of cultivar on beetle emergence was not significant. Root damage was not correlated with adult emergence i n 1994 but was positively correlated in 1995. In 1994, there was no interac tion of the main factors, and all factors had a significant impact on root damage. In 1995 there was an interaction of insecticide and planting date, and of cultivar and planting date. Generally, root damage was reduced by in secticide and later planting. Plant lodging was affected by the interaction of insecticide and planting date, and the interaction of cultivar and plan ting date, for both years of the study. As with root damage, lodging was re duced with insecticide treatment and later planting but also was dependent on cultivar. In 1994 and especially in 1995, silk clipping by adult western corn rootworms precluded much inference about how yield was influenced by larval feeding damage on roots. The number of emerging western corn rootwor m adults was lower and later in later plantings.