Pathogenesis of Entomophaga aulicae: I. Disease symptoms and effect of infection on weight gain of infected Choristoneura fumiferana and Malacosoma disstria larvae

Abstract

Larvae of the eastern spruce budworm, Choristoneura fumiferana, and the forest tent caterpillar, Malacosoma disstria, infected with strains of Entomophaga aulicae gained weight at the same rate as uninfected control larvae and larvae injected with sterile culture filtrates in which E. aulicae had been grown, until the day prior to their death. At this time, infected insects lost weight and exhibited a marked reduction in frass production. No evidence for toxic substances was found in culture filtrates of E. aulicae grown under a variety of environmental conditions nor in homogenates of near or freshly dead E. aulicae-infected budworm larvae. External symptoms of fungal infection on spruce budworm larvae, which first became evident about 4 hr prior to death of the larvae, are described.