LABORATORY BIOASSAYS TESTING THE HOST-RANGE OF THE GYPSY-MOTH FUNGAL PATHOGEN ENTOMOPHAGA-MAIMAIGA

The fungal pathogen Entomophaga maimaiga causes epizootics in gypsy mo th, Lymantria dispar, populations, but little is known about the effec ts of this pathogen on other insect species. The host specificity off. maimaiga was evaluated by externally inoculating larvae with conidia in the laboratory. Larvae were considered successfully infected if E. maimaiga produced spores in/on cadavers. A total of 78 species of Lepi doptera (aside from L. dispar) from 10 superfamilies, predominantly na tives to the Appalachian forests, were challenged during bioassays. Ca davers of 35.6% of the species produced spores after conidial inoculat ion; infection occurred in 7 of the 10 lepidopteran superfamilies test ed, although infection levels were <50% for all superfamilies except B ombycoidea, Sphingoidea, and Noctuoidea. Within both the Bombycoidea a nd Sphingoidea, only one species became infected at >50%. In the Noctu oidea, the Lymantriidae was the only family with high levels of infect ion. Thirty-six of the species exposed to conidia were also injected w ith protoplasts off. maimaiga to determine the contribution of conidia l penetration to species susceptibility. For 23.5% of the species chal lenged using both methods, E. maimaiga could not successfully develop regardless of infection methodology. In 17.6% of the species, E. maima iga did not infect after conidial inoculation but caused high levels o f infection after protoplast injection. An overall analysis found decr eased infection as a result of conidial penetration among larvae with little surface sculpturing and with only primary or short secondary se tae. Conidia produced from cadavers of Danaus plexippus larvae injecte d with protoplasts were infective to L. dispar, suggesting that conidi a produced in alternate hosts are infective. Finally, seasonality of a ctivity of E. maimaiga showed that E. maimaiga spores in soil began ca using infections approximately 2 weeks before L. dispar eggs began hat ching and continued infecting L. dispar larvae in the field through pu pation. (C) 1995 Academic Press, Inc.