A disjunct Californian strain of Entomophaga aulicae infecting Orgyia vetusta.

Fungal epizootics occurred in abundant Orgyia vetusta (western tussock moth; Lepidoptera: Lymantriidae) populations on Lupinus arboreus bushes growing on the Pacific coast north of San Francisco, California. The causative pathogen was isolated and identified as Entomophaga aulicae, Group II, based on RFLPs using rDNA and PCR-amplified rDNA products. Inability of this fungus to infect the lymantriid Lymantria dispar (gypsy moth) confirmed its distinction from Entomophaga maimaiga, the only other member of this species complex which predominantly infects lymantriids. Later instar wandering by O. vetusta in outbreak populations and close proximity of larvae in dense populations are characteristics most probably promoting development of E. aulicae epizootics; these life history patterns are also typical of Lymantria dispar populations experiencing epizootics of E. maimaiga.