Gypsy moth (Lepidoptera: Lymantriidae) control with ground-based hydraulic applications of Gypchek, in vitro-produced virus, and Bacillus thuringiensis

Gypchek, a registered microbial insecticide for aerial and ground-based application against the gypsy moth, Lymantris dispar L., was field-tested in 1996 and 1997 at 2 doses (10(11) and 10(12) polyhedral inclusion bodies (PIB) per 379 liters (100 gallons)) and with and without a sunscreen. An in vitro-produced strain of gypsy moth virus was tested in 1997 at the 10(11)-PIB dose; however, the effective dose was lower because in vitro-produced PIBs contained 5-fold fewer virions than Gypchek PIBs. Treatments were applied to overstory oak, Quercus spp., trees with a truck-mounted hydraulic sprayer. Larval mortality was significantly greater, and larval density was significantly lower, on trees treated with both Gypchek and in vitro-produced virus than on untreated trees. Treatment with in vitro-produced virus resulted in significantly lower mortality and higher larval density than Gypchek treatment. Defoliation was significantly reduced by all treatments in 1996 but not in 1997, when overall gypsy moth population density dropped to very low levels. Mortality was significantly higher among larvae treated at the 10(12)-PIB dose in 1996, but there was no significant dose effect on larval density or defoliation. Mortality, density, and defoliation were not dose dependent in the 1997 test. The addition of sunscreen to Gypchek applied at the 10(12)-PIB dose did not have a significant effect on any of the measured parameters in 1996 or 1997. In 1996, the addition of an enhancer, Blankophor BBH, to the 10(11)-PIB dose increased mortality to a level that was not significantly different from that at the 10(12)-PIB dose. The level of control with the 10(12)-PIB treatment was not significantly different from that achieved with an application of Bacillus thuringiensis subsp. kurstaki Berliner (Foray 48B) at 36 billion international units (BIU) per 379 liters. These results suggest that Gypchek can be used effectively as a ground-based or arborist-applied control agent, and that it ...