Inoculative augmentation of the fungal entomopathogen Entomophaga maimaigaas a homeowner tactic to control gypsy moth (Lepidoptera : Lymantriidae)

Resting spores of the gypsy moth fungal pathogen Entomophaga maimaiga were introduced to four treatment plots on the eastern shore of Maryland in 1995 and 1996 to augment the naturally occurring fungal population. Efforts wer e focused on small. woodlots, characteristic of homeowner properties, where the most intensive management of gypsy moth populations is often practiced . To evaluate results, larvae were sampled from the understory vegetation, under burlap bands, and in the tree canopy. Survival of fifth and sixth-sta ge gypsy moth larvae was always lower in treatment versus control plots alt hough differences were statistically significant on only four of twelve sam pling dates (P < 0.05). Infection by E. maimaiga was always greater in trea tment than in control plots, but due to high variability among plots, these differences were not significant, During 1995, severe defoliation occurred in only one control plot, and numbers of fifth instars were positively ass ociated with the defoliation level. During 1996, no defoliation occurred in any plot because the gypsy moth population collapsed throughout the area. This is the first study sampling gypsy moth larvae throughout the tree cano py to compare the relative distribution of larvae infected by E. maimaiga a nd the Lymantria dispar nuclear polyhedrosis virus (LdNPV), Third through f ifth- and sixth-stage gypsy moth larvae infected with E. maimaiga were more abundant in the understory vegetation than in the tree canopy. Larvae infe cted by LdNPV demonstrated a trend later in the season toward increased occ urrence in the tree canopy than in the understory vegetation, although resu lts were not significant. (C) 1999 Academic Press.