Assemblage of entomopathogenic fungi infesting immature stages of Noctuidae (Lepidoptera): High diversity but low effect on host populations

Populations of herbivorous insects are considered to be primarily regulated by natural enemies. However, little is known about the ecological role of entomopathogenic fungi. There is very little data on the diversity and prevalence of fungal pathogens in natural insect populations. In this study, the percentage mortality attributable to fungal pathogens for the immature stages of three noctuid moths feeding inside the stems of the herbaceous plant, Typha latifolia, were determined. The average percentage mortality caused by fungal pathogens was around 8%, with the value never exceeding 20% at any of the studied sites. As many as ten species of fungi were identified in the 52 infected larvae/pupae collected, this high diversity is consistent with the results of comparable studies. The prevalence of fungal infections did not correlate with host population density or performance of the host insects. This study contributes to the emerging generalisation that populations of insects commonly harbour diverse assemblages of pathogenic fungi, but with low overall prevalence. A significant contribution of these antagonists to regulating insect populations is unlikely.