Host selection of Diachasmimorpha tryoni (Hymenoptera : Braconidae): Comparative response to fruit-infesting and gall-forming tephritid flies

Responses of the opiine larval parasitoid Diachasmimorpha tryoni (Cameron) to the fruit-feeding Mediterranean fruit fly, Ceratitis capitata (Wiedemann ), and the gall-forming lantana gall fly, Eutreta xanthochaeta Aldrich, wer e evaluated in greenhouse and open-door laboratory cages. In greenhouse cag es, coffee plants containing C. capitata-infested fruit and lantana twigs c ontaining E. xanthochaeta galls were presented to gravid D. tryoni under bo th choice and no-choice conditions. Regardless of the type of assay, D. try oni strongly preferred landing on infested coffee plants to landing on gall ed lantana twigs. The wasp also strongly preferred landing on C. capitata-i nfested coffee fruits to E. xanthochaeta galls. In addition, when released directly onto a host-habitat complex, parasitoids had significantly stronge r probing responses to C. capitata-infested coffee fruit than to E. xanthoc haeta galls. However, the stronger probing response to coffee (shorter late ncy and longer duration) by D. tryoni did not result in higher rates of att ack on C. capitata larvae than on gall fly larvae. When measured by the num ber of host larvae attacked per unit time spent probing, D. tryoni was sign ificantly more efficient in attacking lantana gall fly larvae in stem galls than C. capitata larvae in coffee berries. When lantana patches containing galls were presented to D. tryoni in open-door laboratory cages under diff erent regimes of availability of C. capitata or its fruit hosts, rates of a ttack on lantana gall flies by D. tryoni were significantly reduced by the presence of coffee plants containing C. capitata-infested berries. This res ult suggests that host switching of D. tryoni from C. capitata to lantana g all fly in the held is likely to be affected by the spatial and temporal di stributions of the two hosts and their plant habitats. Relevance of our fin dings to host-switching of D. tryoni and the risk of significantly impactin g populations of nontarget lantana gall flies are discussed.