Optimizing natural enemy release rates, and associated pest population decline rates, for Encarsia inaron walker (Hymenoptera: Aphelinidae) and Siphoninus phillyreae (Haliday) (Homoptera: Aleyrodidae)

Field experiments were conducted to evaluate establishment rates and pest and natural enemy population dynamics for four release protocols of the parasitoid Encarsia inaron (Walker). This parasitoid was introduced to California for biological control of the whitefly Siphoninus phillyreae (Gennadius). Two release rates: 1000 or 100 female parasitoids per site; and two release schedules: all females released at once or females released in three equal numbers in 3 consecutive weeks were used. The parasitoid established at all release locations. Rates of establishment, maximum pest densities, year-end pest densities, and rates of pest population decline were not different among the different release protocols. Pest population growth rate was significantly lower at the release sites compared to the control sites, which received no parasitoid releases. Population growth rates for the parasitoid did differ significantly among the treatment sites, with sites receiving greater numbers of initial colonists showing greater growth rates.