Honey-bee-mediated infection of pollen beetle (Meligethes aeneus Fab.) by the insect-pathogenic fungus, Metarhizium anisopliae

Pollen beetles (Meligethes aeneus) are pests that feed and oviposit in the buds and flowers of oilseed rape. Honey-bees foraging from a hive fitted wi th an inoculum dispenser at the entrance effectively delivered dry conidia of the entomogenous fungus, Metarhizium anisopliae, to the flowers of oilse ed rape in caged field plots. In both winter- and spring-sown rape experime nts, a greater mortality of pollen beetles occurred in treated plots than i n control plots. The mortality (61% on winter rape, 100% on spring rape) wa s greatest during peak flowering, what the feeding activity of both bees an d beetles from the flowers was maximal, providing optimal conditions for in oculum dissemination and infection. Conidial sporulation occurred on a sign ificant proportion of the dead pollen beetles. There was no evidence of any adverse effect on the honey-bee colonies.