Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/12/2001
Publication Date: 12/1/2001
Citation: LASTRA, C.C., GIBSON, D.M., HAJEK, A.E. SURVIVAL AND DIFFERENTIAL DEVELOPMENT OF ENTOMOPHAGA MAIMAIGA AND ENTOMOPHAGA AULICAE (ZYGOMYCETES: ENTOMOPHTHORALES) IN LYMANTRIA HEMOLYMPH. JOURNAL OF INVERTEBRATE PATHOLOGY. 2001. v. 78. p. 201-209. Interpretive Summary: Fungal biocontrol agents and biorational pesticides can provide an ecological and safe means of controlling plant pests and reduce dependence on chemical pesticides. Fungi in the order Entomophthorales consist of insect-pathogenic fungi that are highly host-specific. In this study, we used E. maimaiga, a pathogen of gypsy moth, and E. aulicae, a pathogen of grasshoppers, and analyzed for the presence of fungal cells in the interna fluids of gypsy moth. E. maimaiga was able to mount a successful infection, while E. aulicae persisted inside the insect without causing infection. When the cells were removed and cultured outside of the insect, both fungi grew equally well. We found that protein factors within the insect were induced by infection, and that these protein factors could inhibit growth of the fungi. E. aulicae cells were more affected by the protein factors than E. maimaiga cells. This study suggests that protein factors induced within the insect may limit the growth of fungi to develop successful infections.
Technical Abstract: The closely related entomophthoralean fungi Entomophaga aulicae and E. maimaiga are both host-specific pathogens of lepidopteran larvae. However, these fungi do not have the same host range. The first objective of this study was to compare the fate of E. aulicae in the nonpermissive host Lymantria dispar, with the fate of the successful pathogen E. maimaiga over rthe same time period. In the hemolymph of L. dispar injected with E. maimaiga protoplasts, the number of hemocytes demonstrated a decreasing trend after the first day post-injection and hemocytes completely disappeared by day 5, with the majority of larvae dying in 5.6 +/- 0.1 days. In L. dispar larvae, E. maimaiga infections developed successfully, evidenced by increasing numbers of protoplasts and hyphal bodies prior to host mortality. In contrast, at day 5 hemocytes were readily visible in hemolymph of E. aulicae-injected larvae, but E. aulicae cells did not increase in numbers although persisting in the hemolymph for at least 16 days post-injection. When investigating the cause of fungistasis in E. aulicae-injected larvae, E. aulicae cell cultures exposed to partially purified protein fractions from hemolymph of larvae infected with either fungus were more sensitive than E. maimaiga cell cultures. These studies demonstrate that E. aulicae does not increase in L. dispar hemolymph although it persists and results suggest that proteinaceous factors induced within the hemolymph may limit the capacity of E. aulicae to develop successful infections.