Gypsy Moth Control with Dimilin® Sprays Timed to Minimize Effects on the Parasite Apanteles melanoscelus12

Dimilin® (1-(4-chlorophenyl)-3-(2,6 difluorobenzoyl)-urea), an insect growth regulator, was applied by mist blower at 0.0078 lb AI/10 gal water to gypsy moth, blower at 0.0078 lb AI/10 gal water to gypsy moth, Lymantria dispar L., infested apple trees on 3 spray dates when gypsy moth larvae were in stadia 1 and 2, 2 and 3, and 3 and 4, respectively. Percent larval mortality was high on all 3 spray dates. The 1st spray resulted in decreased percent emergence of the larval parasite, Apanteles melunoscelus (Ratzeburg), from the gypsy moth host, while the 2nd and 3rd sprays did not. Six rates of Dimilin between 0.0078 and 0.00025 lb AI/10 gal water were applied similarly on May 29, 1975. Mortality data yielded a significant concentration-response curve for the gypsy moth with the higher rates being comparable in effectiveness to carbaryl at 0.5 lb AI/10 gal water. Residual activity of Dimilin was high for 2 weeks as opposed to one week for carbaryl.