Abstract
Sampling for the gypsy moth fungus, Entomophaga maimaiga, was carried out in 10 plots in Connecticut to determine the importance of overwintering fungal load, rainfall, gypsy moth abundance, and physiographic site conditions to fungal prevalence. At one of the plots, gypsy moths were also exposed daily in cages on the soil and at 2 m in shrubs to examine the pathogen transmission potential of germinating resting spores and of conidia produced by diseased larvae. Gypsy moth population levels and an index of site moisture (as determined by tree composition) were marginally related to fungus prevalence. However, the relationship between fungal prevalence and population was an inverse one, opposite that found in a previous study. Resting spore load did not appear to affect prevalence; it is possible that a threshold effect occurs. Daily sampling showed that germination of resting Spores is necessary for infection of early-stage larvae, but that conidia produced from diseased larvae are mainly responsible for infection of late-stage caterpillars. Maximum germination of resting spores occurred 1 or 2 d after significant precipitation, whereas the greatest production of conidia from diseased caterpillars took place on the day of rainfall. We hypothesize that in areas where overwintering resting spores are abundant, the most important determinant of fungal effectiveness will be rainfall amount and pattern.
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