Target-oriented dissemination ofBeauveria bassianaconidia by the predators,Harmonia axyridis(Coleoptera: Coccinellidae) andChrysoperla carnea(Neuroptera: Chrysopidae) for biocontrol ofMyzus persicae

Abstract

Dissemination of microbial biocontrol agents via predators may have advantages for safe spore dispersal to targeted pests with the added benefit of predation. A laboratory study was conducted to test the target-oriented dissemination of conidia of Beauveria bassiana using larvae of both the multicoloured Asian lady beetle (Harmonia axyridis) and common green lacewing (Chrysoperla carnea) for control of aphids. Maximum dry conidial attachment occurred within approximately 7 min after exposure. After release of the treated predators on leaves of Chinese cabbage, within 12 hours lacewing larvae dispersed 89% of the attached conidia while Asian lady beetles dispersed 93%. Both predators dispersed conidia up to 2.4 m from the release site. Leaf disk bioassays were conducted to compare two application methods; the dissemination of conidia of B. bassiana by predators and the direct application of conidial suspensions. Mortality in sprayed aphids was 91±2.1% compared to 88±2.1 and 84±4.2%, respectively, when conidia were disseminated by lacewings and lady beetles. Predation was not affected in treated lacewing larvae whereas there was a 20% reduction in predation by lady beetle larvae. It appears that B. bassiana can be effectively delivered using certain insect predators.