Retarding outbreak of low-density gypsy moth (Lepidoptera: Lymantriidae) populations with aerial applications of Gypchek and Bacillus thuringiensis

Low-density gypsy moth, Lymantria dispar (L.), populations in Virginia were aerially treated with the nucleopolyhedrosis virus (baculovirus) product Gypchek and with a commercial preparation (SAN 415 SC 32LV) of the NRD-12 strain of Bacillus thuringiensis (Kurstak). Six 12.2-ha plots received two applications of Gypchek, each at the rate of 1.25 X 10(12) occlusion bodies in 18.7 liters of an aqueous tank mix per ha. Six 12.2-ha plots received two neat applications of SAN 415, each at the rate of 49.4 BIU in 5.96 liters per ha. Gypchek and SAN 415 treatments reduced numbers of egg masses by 92 and 94%, respectively, compared with numbers in six control plots. Weekly counts of live larvae found under burlap bands were significantly lower in Gypchek- and SAN 415-treated plots than in control plots, but defoliation differences between sprayed and control plots were not significant. Control plots displayed a second wave of larval mortality from naturally occurring nucleopolyhedrosis virus that was different from that seen in plots treated with Gypchek and SAN 415