Response of Two Opiine Fruit Fly Parasitoids (Hymenoptera: Braconidae) to the Lantana Gall Fly (Diptera: Tephritidae)

Abstract

The lantana gall fly, Eutreta xanthochaeta Aldrich, is an introduced biological control agent that has been successfully established in Hawaii and has contributed to the suppression of the noxious weed Lantana camara (L.). We evaluated responses of the introduced fruit fly parasitoids Diachasmimorpha longicaudata (Ashmead) and Psytallia fletcheri (Silvestri) to field-collected late instars of E. xanthochaeta to determine potential nontarget effects. Gravid females of D. longicaudata and P. fletcheri were confined in laboratory cages with the larvae of E. xanthochaeta contained in different substrates. Females of both species of parasitoids showed positive ovipositional responses to the larvae of E. xanthochaeta. However, response to and subsequent parasitization of E. xanthochaeta were influenced significantly by the exposure substrate. E. xanthochaeta contained in intact galls (the natural substrate) received significantly fewer stings and actual ovipositions from D. longicaudata and P. fletcheri than those contained in artificially shaved galls, or in screen-covered dishes containing artificial diets of the parasitoids' normal fruit fly hosts. Upon successfully depositing eggs into E. xanthochaeta larvae, D. longicaudata developed into normal males and females with a sex ratio of 1:1.8. However, for unknown reasons, eggs of P. fletcheri were unable to hatch. The relevance of our findings to the safety of future augmentative parasitoid releases is discussed.