Changes in population density of Aleurocanthus camelliae (Hemiptera: Aleyrodidae) and parasitism rate of Encarsia smithi (Hymenoptera: Aphelinidae) during the early invasion stages

Invasive pest insects are often controlled by non-native natural enemies introduced from the original home range of the target pests. The non-native parasitoid wasp Encarsia smithi (Silvestri), which naturally migrated to tea plantations in Japan, is a potential agent for the biological control of the invasive camellia spiny whitefly Aleurocanthus camelliae Kanmiya & Kasai. To evaluate the effectiveness of E. smithi as a pest control agent, we surveyed 27 tea plantation sites in Shizuoka Prefecture, Japan to identify any changes in the population densities of A. camelliae 1–3 years after the initial detection in 2010 and also to estimate the parasitism rates of E. smithi. The results suggested that parasitism by E. smithi considerably affected the field mortality rates of A. camelliae. Wasps rapidly spread to the region where whiteflies expanded their distribution and controlled population outbreaks in many sites. However, at some sites where the population density of A. camelliae increased rapidly, the parasitism rates of E. smithi tended to remain at low levels or declined. Overall, our results suggest that parasitism by E. smithi could be used as an effective measure for the control of A. camelliae populations in tea plantations.