Effect of aerial spraying with Dimilin, Dipel, or Gypchek on two natural enemies of the gypsy moth (Lepidoptera: Lymantriidae)

The effects of three aerially applied insecticides on the incidence of two components of the natural enemy complex of the gypsy moth, Lymantria dispar (L.), were evaluated for the 1987 year of application. Application of Gypchek, a registered formulation of the gypsy moth nuclear polyhedrosis virus (NPV), initiated a large early-season (fist-wave) epizootic of NPV; late-season NPV (second-wave) levels were higher in plots treated with Gypchek than in control plots, but not significantly so, whereas levels of the parasitoid Cotesia melanoscela (Ratzeburg) were significantly reduced in Gypchek-treated plots compared with control plots. Application of Dipel (Bacillus thuringiensis Berliner) resulted in a significant increase in numbers of C. melanoscela. Application of either Dipel or Dimilin (diflubenzuron) resulted in a significant decrease in incidence of NPV compared with control plots. Numbers of C. melanoscela in plots treated with Dimilin were not significantly different from those detected in control plots