Effects of the microsporidium Nosema adaliae from Adalia bipunctata L. on the multicoloured Asian lady beetle Harmonia axyridis Pallas

Abstract

Originally imported for use as a biological control agent for pest insects, the multicoloured Asian lady beetle Harmonia axyridis has itself become a pest in many areas. While it is a very successful biological control, it has many non-target impacts such as displacement of native species of lady beetles and it can have adverse effects on human health. The geographic distribution of H. axyridis in Nova Scotia overlaps with the range of the native two-spotted lady beetle, Adalia bipunctata. This overlap provides the opportunity for the microsporidian pathogen Nosema adaliae to be horizontally transmitted to H. axyridis. In this study, H. axyridis larvae were allowed to consume a mixture of uninfected and infected A. bipunctata eggs. All H. axyridis larvae that consumed infected eggs were infected by the pathogen. Larval development was significantly prolonged for those larvae that consumed four infected eggs. These results suggest that H. axyridis has some resistance to the effects of N. adaliae since it requires the consumption of four infected eggs to significantly delay larval development.