The fungal pathogen Entomophaga maimaiga (Zygomycetes: Entomophthorales) has been responsible for significant declines in gypsy moth Lymantria dispar L. (Lepidoptera: Lymantriidae) defoliation in the northeastern U.S. since 1989. It has relatively few negative effects on non-target species, and is compatible with other natural enemies including the gypsy moth nucleopolyhederosis virus (NPV), making E. maimaiga a desirable biocontrol agent. In Michigan, however, the pattern of E. maimaiga epizootics has been less consistent since its introduction in 1991. Although E. maimaiga is established throughout Michigan, high-density gypsy moth populations and severe defoliation have continued to occur. We conducted large-scale field bioassays in 32 oak-dominated Michigan forests across regions with varying weather patterns, known to have been previously inoculated with E. maimaiga, to assess infection rates of laboratory-reared gypsy moth larvae. We also conducted laboratory bioassays with gypsy moth larvae on soil samples collected from the 32 study sites to determine infection rates under optimal fungal germination conditions. Soil samples were analyzed to quantify the density of E. maimaiga resting spores at each of the study sites. Additionally, we collected larval cadavers from the natural gypsy moth populations at the bioassay sites to evaluate the interactions between E. maimaiga and NPV. Preliminary results from field bioassays indicate that differences in E. maimaiga infection rates exist between regions. Preliminary results from laboratory bioassays indicate that E. maimaiga infection rates under optimal conditions were greater than those observed under field conditions. Additionally, regional differences in E. maimaiga infection rates were not significant in laboratory bioassays. Preliminary results from field and laboratory bioassays indicate that E. maimaiga infection rates did not significantly differ between aspects. Approximately 76% of the gypsy moth cadavers collected from the naturally occurring populations were co-infected with E. maimaiga and NPV.
Species 1: Zygomycetes Entomophthorales Entomophaga maimaiga (gypsy moth fungus)
Species 2: Lepidoptera Lymantriidae Lymantria dispar (gypsy moth)
Keywords: biological control, forest entomology
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA