Occurrence, Density, and Distribution of Parasitic Fungus <I>Hesperomyces virescens</I> (Laboulbeniales: Laboulbeniaceae) on Multicolored Asian Lady Beetle (Coleoptera: Coccinellidae)

Abstract

The coccinellid-specific parasitic fungus Hesperomyces virescens Thaxter was found on the multicolored Asian lady beetle, Harmonia axyridis (Pallas), in fall and winter in Lebanon County, Pennsylvania. Research objectives were 1) to determine the density of H. virescens on field-collected H. axyridis adults held in the laboratory, and 2) to determine H. virescens presence, density, and distribution on H. axyridis adults in the field. In the laboratory, male and female H. axyridis adults hosted >150 H. virescens mature thalli (i.e., fruiting bodies); distributed primarily on the elytra and abdomen. At the overwintering site, H. virescens density per host was often <20 mature thalli, which were distributed primarily on the elytra of both sexes. On average, 52.5 and 57.4% of H. axyridis males and females, respectively, hosted H. virescens mature thalli in late winter (5 March 2003); <14% of either sex hosted mature thalli the following fall (15, 22, and 28 October and 10 November 2003) at the same site. This study suggests that H. virescens is an established parasite of H. axyridis in Pennsylvania but that field estimates of infection may vary considerably between dates that adult beetles arrive and depart from overwintering sites. Preponderance of fungal thalli on the dorsum rather than the ventrum of H. axyridis males suggests that mating behavior is not solely responsible for transmission of H. virescens from infected to noninfected adults.