Grantee Research Project Results
Impact of Bacillus thuringiensis Application on Entomophaga maimaiga-Induced Mortality of Gypsy Moth (Lepidoptera: Lymantridae)EPA Grant Number: U915150
Title: Impact of Bacillus thuringiensis Application on Entomophaga maimaiga-Induced Mortality of Gypsy Moth (Lepidoptera: Lymantridae)
Investigators: Mott, Molly A.
Institution: Michigan State University
EPA Project Officer: Smith, Bernice
Project Period: January 1, 1997 through January 1, 1999
Project Amount: $68,000
RFA: STAR Graduate Fellowships (1997)
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Entomology
The objective of this research project is to demonstrate that late-season, Entomophaga maimaiga-induced mortality of gypsy moth will be lower in Btk-sprayed plots due to the reduction of early instar larval density. E. maimaiga (Zygomycetes: Entomophthorales) is a virulent fungal pathogen of gypsy moth larvae. Although interactions of E. maimaiga with another natural enemy—the gypsy moth nuclear polyhedrosis virus—have been explored, the relationship with Bacillus thuringiensis var. kurstaki (Btk), a biological insecticide commonly used for gypsy moth suppression, has not been investigated. Because Btk is applied in early spring, when first and second instar larvae are present, fewer larvae may be available for primary infection by the fungus and subsequent production of secondary inoculum for further infection through the season.Approach:
Three sites containing at least 60 percent oak forest were selected for study. E. maimaiga was found throughout this region of the state in 1996. One-half of each site was randomly chosen for aerially spraying with Btk through the state suppression program. Two plots per treatment block (sprayed or control) were randomly chosen for sampling and larval density estimation (3 plots for egg mass densities). Gypsy moth was monitored from egg hatch to 50 percent pupation. Initial soil resting spore density and initial and final egg mass density were determined. Burlap banding was used for sampling and density estimation from these low populations. The density of live and dead larvae was estimated each week by timed counts. Larvae were collected weekly, held on diet, and dissected upon death to determine whether E. maimaiga or other pathogens were present. Precipitation and temperature extremes were recorded from the nearest weather station. Aerial conidia were sampled actively with a Burkhard volumetric spore sampler and passively with dry slides.Supplemental Keywords:
fellowship, Bacillus thuringiensis, Btk, Entomophaga maimaiga, gypsy moth, fungal pathogen, larvae, insecticide.