Functional response and instar preference of Encarsia formosa (Hymenoptera: Aphelinidae) parasitizing Bemisia tabaci (Hemiptera: Aleyrodidae) at different densities and temperatures

Bemisia tabaci (Gennadius) is among the most serious threats to global agricultural production. Biological control of B. tabaci using the parasitoid Encarsia formosa Gahan is effective on various crops. However,the biological control of B. tabaci could be affected by various abiotic factors. Understanding the effects of temperature on parasitoid efficacy is one of the key ascpects in this case. In this study, the functional response, searching efficiency, and parasitism preference of E. formosa on early and late nymphal instars of B. tabaci at different temperatures were investigated. We found that the functional response conformed to the type II model at 19, 22, 25, 28 and 31 °C. The parasitoid efficiency of E. formosa toward nymphal B. tabaci was the highest at 28 °C. Searching efficiency of E. formosa decreased with the increase in host density. The Hassell-Varley interference model simulation indicated intraspecific interference in E. formosa. E. formosa preferred to parasitize late instar nymphs of B. tabaci compared to the early instar nymphs. In conclusion, E. formosa releases at 25–31 °C with a parasitoid-to-host ratio of 1:50 is considered optimal to control B. tabaci in field, which minimizes costs and maximizes parasitism rate.