Single Applications of High Concentrations of Bacillus thuringiensis for Control of Gypsy Moth (Lepidoptera: Lymantriidae) Populations and Their Impact on Parasitism and Disease1

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Abstract
In aerial spray trials with Bacillus thuringiensis Berliner conducted against dense populations of Lymantria dispar (L.), single applications of 12 and 16 BIU/0.4 ha gave significant reductions in larval density and excellent foliage protection. Less than 4% net defoliation was observed in treated plots, compared with 69% in untreated plots; this level of control was equivalent to that achieved with two weekly applications at 8 BIU/0.4 ha. Good results were attributed to the formulation, application before the majority of larvae had matured beyond the 2nd in star, thorough spray coverage, and use of an effective sticker. Observations on the natural prevalence of nucleopolyhedrosis virus and parasitism by larval and pupal parasitoids in the treated gypsy moth populations indicated a good compatibility of B. thuringiensis with the major natural enemies which help regulate the population.