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Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/18/2003 Publication Date: 11/15/2003 Citation: Cottrell, T.E., Shapiro Ilan, D.I. 2003. Susceptibility of a native and an exotic lady beetle (Coleoptera: (Coccinellidae) to Beauveria bassiana. Journal of Invertebrate Pathology. 84:137-144. Interpretive Summary: Successful establishment of natural enemies for biological control of pests depends upon various factors (e.g., host suitability, climate and/or habitat) but definitive reasons generally are not known. Surprisingly, the impact of native insect pathogens upon establishment of these biological control agents, such as lady beetles, has not been studied. We discovered that a native lady beetle, Olla v-nigrum, was commonly infected by a fungal pathogen, Beauveria bassiana, whereas the recently-established and widespread multicolored Asian lady beetle, Harmonia axyridis, was not. Laboratory tests revealed that B. bassiana isolates collected from naturally infected O. v-nigrum were pathogenic to O. v-nigrum but not H. axyridis. In contrast, a commercially-available strain of B. bassiana was not significantly pathogenic to O. v-nigrum nor H. axyridis. Late season field collections revealed significantly higher B. bassiana infection of O. v-nigrum than H. axyridis. Our results suggest that establishment of H. axyridis in North America was facilitated by a dearth of pathogens adapted to attack the exotic lady beetle. Technical Abstract: Successful establishment of natural enemies for biocontrol of pests depends upon various factors (e.g., host suitability, climate and/or habitat) but definitive reasons generally are not known. Surprisingly, the impact of endemic entomopathogens upon establishment of biocontrol agents, including Coccinellidae, has not been studied. Entomopathogens impacting natural enemies typically are discussed in terms of their safety as biorational products to non-target species. We discovered that a native coccinellid, Olla v-nigrum, was commonly infected by Beauveria bassiana whereas a recently-established and widespread exotic coccinellid, Harmonia axyridis, was not. Laboratory assays revealed that B. bassiana isolates collected from naturally infected O. v-nigrum were pathogenic to O. v-nigrum but not H. axyridis. In contrast, the GHA strain of B. bassiana was not significantly pathogenic to O. v-nigrum nor H. axyridis. Late season field collections revealed significantly higher B. bassiana infection of O. v-nigrum than H. axyridis. Our results suggest that establishment of H. axyridis in North America was facilitated by a dearth of entomopathogens. |
