The effect of manuka honey on two-spotted lady beetle larvae, Adalia bipunctata L. (Coleoptera: Coccinellidae), infected with a microsporidian pathogen

Abstract

The full potential of biological control agents, such as the two-spotted lady beetle, Adalia bipunctata L., against insect pests greatly depends on the ability of the control agent to successfully mature to adulthood. Intracellular pathogens such as microsporidia, affect larval growth and development. Differences in food quality and quantity can also affect larval growth and development, as well as reproduction. The aim of this research is to determine whether the effects of the microsporidian pathogen, Nosema adaliae, is mitigated when its host, A. bipunctata, is reared on mixed diet of green peach aphid (Myzus persicae Sulzer) and antimicrobial manuka honey. Development and mortality of infected lady beetles were compared between four different treatment groups: the control group was provided aphids and water, whereas the three treatment groups were given aphids and three different dilutions of honey (5%, 10% and 15%), depending on the treatment. Larval development for the control was 15.9 ± 0.7 SE days, whereas larval development for the treatment groups was 13.8 ± 0.6, 13.8 ± 1.0, and 13.3 ± 0.9 days for larvae that were provided with 5%, 10% and 15% manuka honey, respectively. Our results indicated that the addition of manuka honey into the diet of infected A. bipunctata resulted in a decrease in larval development time while mortality and sex ratio were unaffected. This suggests that the addition of non-prey food such as manuka honey to an essential diet of M. persicae can shorten the larval development period. Further quantitative analysis would determine if there is a direct impact of manuka honey on the pathogen.