Entomophaga maimaiga (Zygomycete: Entomophthorales) resting spores and biological control of the gypsy moth (Lepidoptera: Lymantriidae)

Abstract

Neonate and larger gypsy moth, Lymantria dispar (L.), larvae were collected in a forest and exposed in the leaf litter and trees to determine proportions infected by the fungal pathogen Entomophaga maimaiga Humber, Shimazu and Soper. Results were used to refine a previously developed model of fungus infection of gypsy moths. The revised model only allowed infection of 4th- and larger instar gypsy moths through the germination of resting spores. Infection of neonates via germinating resting spores and of larger gypsy moths through release of conidia from sporulating cadavers was not included because adequate information about transmission rates were not available. This model produced a generally good fit to weekly infection data obtained from collected early to midsized gypsy moth larvae in 1990, 1991, and 1998, so long as a multiplying parameter that did not change the shape of the curve was permitted to vary. This parameter was correlated with a measure of infection caused by resting spores. The intensity of spore germination and resulting infection in the forest is an important predictor of infection by this fungus of early to midsized gypsy moth larvae, and ways to measure the infection potential of such spores before gypsy moth larvae hatch in the spring would greatly aid efforts to predict the impact of this biological control agent.