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) o f the NRD-12 strain of Bacillus thuringiensis (Kurstak). Six 12.2-ha p lots 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 th e rate of 49.4 BIU in 5.96 liters per ha. Gypchek and SAN 415 treatmen ts 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-t reated plots than in control plots, but defoliation differences betwee n sprayed and control plots were not significant. Control plots displa yed a second wave of larval mortality from naturally occurring nucleop olyhedrosis virus that was different from that seen in plots treated w ith Gypchek and SAN 415.