HOST-RANGE OF THE GYPSY-MOTH (LEPIDOPTERA, LYMANTRIIDAE) PATHOGEN ENTOMOPHAGA-MAIMAIGA (ZYGOMYCETES, ENTOMOPHTHORALES) IN THE FIELD VERSUS LABORATORY

Lepidopteran larvae were sampled in the field to determine levels of i nfection by the gypsy moth, lymantria dispar (L.), fungal pathogen, En tomophaga maimaiga Humber, Shimazu & Soper. Lepidopteran larvae were r eared from 7 plots in Virginia in which moderate density gypsy moth po pulations simultaneously exhibited from 40.8 to 97.5% E. maimaiga infe ction. From a total of 1,511 larvae from 52 species belonging to;lepid opteran families in 4 superfamilies, only 2 individuals, 1 of 318 fore st tent caterpillars, Malacosoma disstria Hubner (0.3% infection), and 1 of 96 Catocala ilia (Cramer) (1.0% infection), became infected by e ntomophthoralean pathogens. Results from genomic DNA probes and bioass ays confirmed that E. maimaiga had caused these infections. Laboratory studies yielded infection over a greater diversity of species, and pe rcentages of infection from laboratory studies were higher than findin gs from the field for the 1 species infected in both the laboratory an d field. At all sites, the gypsy moth nuclear polyhedrosis virus also was found, occasionally causing epizootics, but viral occlusion bodies were never found in nontarget Lepidoptera that died. In addition, 279 nontarget Lepidoptera belonging to 34 species in 8 families were coll ected and reared from areas with low density native gypsy moth populat ions, and E. maimaiga infections were not found in these nontarget hos ts, although E. maimaiga was active in gypsy moth populations. A surve y of lepidopteran cadavers collected from 1989 to 1995 containing ento mophthoralean spores documented E. maimaiga infections in 3 species of lymantriids. The Lepidoptera-specific North American endemic entomopa thogen Entomophaga aulicae (Reichardt in Bail) Humber, which is morpho logically identical to E. maimaiga, was found in 1 geometrid species, 1 notodontid, 2 species of arctiids, and 1 introduced lymantriid, but in none of the gypsy moth larvae tested. Our results demonstrate that data from laboratory bioassays are poor estimates for predicting nonta rget impact.