Host selection of Dolichogenidea tasmanica: implications for conservation biological control of light brown apple moth

An understanding of host selection by parasitoids can help in evaluating alternative host candidates to make conservation biological control of a target pest more reliable. This study investigated the host selection behaviour of Dolichogenidae tasmanica (Hymenoptera: Braconidae) in response to two related tortricid host species (Lepidoptera). The light brown apple moth, Epiphyas postvittana is the biological control target in Australian vineyards, while Merophyas divulsana was selected to evaluate its potential as an alternative host. We quantified the effects of host species, ages and experiences on the landing preferences of the parasitoid in dual choice tests. The effects of these host species on developmental time, sex ratio and body size of adult parasitoids were also examined. During all observations, D. tasmanica exhibited no statistically significant preferences in response to these hosts. Host species did not affect the body size of the wasp, but did influence its developmental time, possibly due to a trade-off between body size and developmental time of the wasp, which took longer in the smaller host, M. divulsana. The sex ratio was similar within host instars and between host species. These results suggest that M. divulsana should be a promising alternative host to support the local parasitoid population in vineyards as part of a conservation biological control programme that targets E. postvittana.