Risk of infection by the fungal pathogen Entomophaga maimaiga among Lepidoptera on the forest floor

The entomopathogenic fungus Entomophaga maimaiga causes epizootics in gypsy moth, Lymantria dispar (L.), populations and persists in forests as a rese rvoir of spores in soil at the bases of trees. To investigate whether E. ma imaiga infects Lepidoptera living in leaf litter, we collected and reared l arvae in leaf litter, understory vegetation, and on tree boles within a 200 -cm radius around trunks of red oak, Quercus rubra L., trees. Among the 358 lepidopteran larvae reared, only one gelechiid larva (out of 84 collected) and one larva of the noctuid Sunira bicolorago (out of 20 individuals from this species) were infected by E, maimaiga. Our collections included 67 gy psy moth larvae, of which 25 (37%) were infected by E. maimaiga. The majori ty of infected gypsy moth larvae were collected during the second half of J une, when few nontarget Lepidoptera were present in the oak leaf litter. A bioassay of Zanclognatha laevigata Grote, a herminiine noctuid whose larvae spend their entire lives in leaf litter, yielded no infection. Because lab oratory host specificity studies had demonstrated high levels of infection only in lymantriid larvae, we also caged larvae of the lymantriid Orgyia le ucostigma (J. E. Smith) over soil at the bases of trees or in understory ve getation. Levels of infection for O. leucostigma remained consistently lowe r than among caged gypsy moth larvae, and infection was always higher in th e soil than on the understory vegetation. We conclude that, aside from gyps y moth larvae, E. maimaiga infections among litter-dwelling lepidopteran la rvae were rare, and we hypothesize that infection of other lymantriids in t he field will depend on whether they visit the ground level for a significa nt period of time.