Field Investigation of a Baculovirus of the Gypsy Moth12

Abstract

Nuclear polyhedrosis virus was applied by ground and aerial methods to oak forests infested with Lymantria dispar (L.) in Pennsylvania. Two ground applications were made at l×1013 polyhedral inclusion bodies/0.405 ha. Efforts were made to determine the post treatment residual activity. Significant larval reduction resulted in the dense population virus treated site. In the dense and artificially infested plots, a significantly greater number of virus killed larvae were found in the treatment when compared with the control. Some foliage protection was afforded by the virus application to the artificially infested site and resulted in a 90% reduction in egg masses compared with a 65% increase in the untreated. Untreated plots had 10 times more egg masses than the treated plots one year following application. Over 32% of the larvae reared from egg masses obtained from the virus treated plots died of virus infections. When a single virus application was made by air, significantly fewer larvae were found in the treatments than in the controls. Virus treated plots were defoliated 50–75%, while untreated areas were almost completely defoliated.