PARASITIZATION OF MELON FLY (DIPTERA:TEPHRITIDAE) BY FOPIUS ARISANUS AND PSYTTALIA FLETCHERI (HYMENOPTERA:BRACONIDAE) AND THE EFFECT OF FRUIT SUBSTRATES ON HOST PREFERENCE BY PARASITOIDS

Authors: Bautista, Renato; Harris, Ernest; Vargas, Roger; Jang, Eric

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2004
Publication Date: 6/1/2004
Citation: Bautista, R.C., Harris, E.J., Vargas, R.I., Jang, E.B. 2004. Parasitization of melon fly (diptera:tephritidae) by fopius arisanus and psyttalia fletcheri (hymenoptera:braconidae) and the effect of fruit substrates on host preference by parasitoids. Biological Control. 30:156-164.

Interpretive Summary: The U.S. Pacific Basin Agricultural Research Center, USDA-ARS, in collaboration with the University of Hawaii and State Department of Agriculture, has implemented an IPM program to demonstrate area wide suppression of tephritid fruit flies in Hawaii. A package of control strategies including augmentative releases of the larval parasitoid Psyttalia fletcheri was initiated over a 40-Km grid site in Kamuela, island of Hawaii to stifle melon fly (Bactrocera cucurbitae) infestation. As we progress in our program, releases of the egg parasitoid Fopius arisanus in concurrence with P. fletcheri may be an option in our strategy. However, because the outcome of a biological control tactic is predicated on how different parasitoids might interact with one another, this study was undertaken to determine the potential consequences that may happen should F. arisanus and P. fletcheri were released simultaneously. Information was generated on survival and mortality of melon fly with a life table, effects of multiparasitism on progeny survival of parasitoids, and influence of fruit substrates on host preference by parasitoids. Our study demonstrated that parasitization by F. arisanus or P. fletcheri alone could effectively suppress development of potential melon flies by as much as 52% and 56%, respectively; that when both parasitoids attacked fruit fly eggs and larvae in concert (sequential parasitism), the level of control exerted on developing flies was considerably higher (>90%) than anticipated; that while F. arisanus produced very few progeny on melon fly, the direct kill and/or latent host mortality associated with female oviposition had a tremendous impact on melon fly development. In addition, a preference for hosts infesting certain fruit types could play a role in enhancing effectiveness of released parasitoids in a diverse habitat. This information provided a basis for undertaking parasitoids releases that may involve F. arisanus and P. fletcheri in a melon fly suppression program.

Technical Abstract: Fopius arisanus (Sonan) (=Opius oophilus Fullaway) and Psyttalia (=Opius) fletcheri (Silvestri) are egg and larval parasitoids, respectively, of tephritid fruit flies including the melon fly, Bactrocera cucurbitae (Coquillett), a persistent pest of cucurbitaceous and other vegetable crops. We investigated the consequences of parasitization when eggs or larvae of melon flies were exposed to F. arisanus or P. fletcheri alone, or to both in succession. In addition, the effect of fruit substrates on host preference by gravid parasitoids was evaluated. F. arisanus readily parasitized 45% melon fly eggs after a 24-h exposure period to gravid parasitoids. The proportion of parasitized hosts increased two-fold to >90% when melon fly larvae were exposed to P. fletcheri alone, or when host immatures (eggs then larvae that subsequently developed from the same cohort) were exposed sequentially to both parasitoids. While P. fletcheri developed freely on melon fly, F. arisanus was less successful and rarely produced progeny of its own. Life table calculations indicated that parasitization by F. arisanus resulted in host kills of 38, 40, and 47% in egg, larval, and pupal states of the melon fly, respectively, while parasitization by P. fletcheri resulted in larval and pupal mortalities of 24 and 79%, respectively. Sequential exposure of melon fly eggs to F. arisanus, then larvae to P. fletcheri, resulted in host kills of 52, 56 and 91% during the egg, larval and pupal stages, respectively. Parasitization by either F. arisanus, P. fletcheri, or both, suppressed melon fly development by 2-, 5-, and 12-fold, respectively. Given a choice of fruit cultivars, F. arisanus and P. fletcheri preferred melon fly in zucchini squash. Cucurbita pepo L., over melon flies that occurred in Japanese eggplant (long purple), Solamum melongena L.; Chinese bitter melon, Mamordica charantia L.; Japanese cucumber, Cucumis sativus L.; and garden tomato, Lycopersicon esculentum Miller. This study provides a basis for better understanding future work that may involve single or multi-species releases of parasitoids for biological control of the melon fly.