Prevalence and biology ofFuria gastropachae(Zygomycetes: Entomophthorales) in populations of forest tent caterpillar (Lepidoptera: Lasiocampidae)

Abstract

AbstractFuria gastropachaecomb. nov.(=Furia crustosaMacLeodetTyrrell) has long been associated with declines in populations of the forest tent caterpillar,Malacosoma disstriaHübner; however, its prevalence and impact on host populations have never been documented. We clarify the nomenclature for this species, which has previously been calledF. crustosa, and describe the morphology ofF. gastropachaeisolates from Maryland and New York. Epizootics ofF. gastropachaewere studied inM. disstriapopulations in New York and Maryland, United States of America. Prevalence (mean ± SE) ofF. gastropachaein late fifth instar larvae in New York was 25.6 ± 7.8% compared with 22.2 ± 11.3% infection by virus and 23.3 ± 8.4% parasitism. In Maryland,F. gastropachaewas not found in early instars and its incidence in fourth and fifth instars was 14.5 ± 7.3 and 21.6 ± 17.6%, respectively. Dipteran parasitoids were also important natural enemies with 38.3 ± 3.0 and 17.9 ± 1.4% parasitism in fourth and fifth instars, respectively. Virus was found in fewer than 5% of larvae collected.Furia gastropachaeshowed a marked tendency toward resting spore production in infected larvae, with 100% of larvae collected in New York and >80% of larvae collected in Maryland producing resting spores, either alone or in combination with conidia. The appearance of cadavers of larvae dying from fungal and viral infections was similar. Of 13 species of Lepidoptera exposed toF. gastropachaeconidia in host-range bioassays, only 3.3% ofDanaus plexippus(L.) (Lepidoptera: Danaidae), 5.6% ofPieris rapae(L.) (Lepidoptera: Pieridae), and 3.7% ofManduca sexta(L.) (Lepidoptera: Sphingidae) were successfully infected by this fungus.