Interspecific Competition between Two Exotic Parasitoids (Hymenoptera: Aphelinidae) of an invasiveBemisia tabaciSpecies (Hemiptera: Aleyrodidae)

Abstract

Classical biocontrol programs usually employ multiple species to control a single pest; however, the beneficial effects are not always additive due to competition between the introduced species. Knowledge of these potentially negative interactions is crucial when determining whether the introductions were successful and the extent to which they influence pest suppression. Here, we report the results of such competition between 2 exotic wasp species [Encarsia bimaculata Heraty & Polaszek and Eretmocerus sp. nr. emiratus (Hymenoptera: Aphelinidae)] introduced into Florida for control of the circumglobal super pest currently known as Middle East-Asia Minor 1, a cryptic species within the Bemisia tabaci complex (Hemiptera: Aleyrodidae). Levels of parasitism, progeny production, and host feeding were evaluated in the laboratory under various parasitoid combinations on 2 host plant species (collard and eggplant) that differed in leaf pilosity (i.e., number of trichomes on the abaxial leaf surface). Significant differences in parasitism were observed by treatment, but not host plant. Encarsia bimaculata produced fewer progeny when introduced before Er. sp. nr. emiratus on collard; however, this trend was reversed on eggplant. Eretmocerus sp. nr. emiratus produced less progeny in all combinations involving En. bimaculata on collard and when introduced before En. bimaculata on eggplant. Mortality caused by host feeding was atypical for the whiteflyparasitizing aphelinids (<5% in all treatments). Based on differences in parasitism and progeny production, no additional pest suppression would be gained by releasing En. bimaculata into an environment already under control by Er. sp. nr. emiratus.

Combined use of the larvo‐pupal parasitoids Diachasmimorpha longicaudata and Aganaspis daci for biological control of the medfly

“…The use of multiple species to control a single insect pest is very common within biological control programmes. Nevertheless, this approach does not always lead to improved control of the target pest because of negative interactions among the selected biocontrol agents (Lahey et al, ). Some studies have suggested that there is no cumulative pest control when multiple parasitoid species are released because of the above‐mentioned negative interactions (Briggs, ; Denoth et al, ).…”

“…Biological control programmes typically involve the use of multiple species to control a single target pest (Denoth, Frid, & Myers, ; Gould, Hoelmer, & Goolsby, ); however, the beneficial effects are not always additive because of competition between the species (Lahey, McAuslane, & Stansly, ). In this regard, interspecific competition is considered a common phenomenon in parasitoid Hymenoptera, many of which develop on a single host (Yang et al, ).…”