The Western Spotted Cucumber Beetle as a Pest of Forage Crops in the Pacific Northwest

Abstract

Adults of Diabrotica 11-punctata destroy seedling red clover in Mar. and Apr. Larvae damage young alfalfa and corn to late May. Female beetles sometimes congregate in hibernation sites near water. Mating of new generation beetles occurs in late summer and most of the [male][male] die before spring when eggs are laid. Eggs in cracks in the soil hatch, according to temp., in 8-22 days. Larval development takes 3 weeks, followed by non-feeding prepupal and pupal stages. Development from egg to adult takes 50-75 days. Roots of various plants nourish the larvae. The beetles have more varied foods, but the food of ovipositing [female][female] appears to affect longevity and fertility. There is only 1 generation in a yr. in the Willamette Valley and some overwintered [female][female] lay > 1000 eggs from early spring to late summer. Natural checks are deficient soil moisture, winter cold, Celatoria diabroticae, a mermithid, Beauveria globulifera, and birds. Beetles in winter concs. can be destroyed by fire or 1% rotenone dust. Delayed seeding avoids damage to clover, alfalfa and com.