Classical biological control of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), (Diptera:Tephritidae): natural enemy exploration and nontarget testing



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Texas A&M University


This work covers stages one through seven (of nine stages) of a classical biological control program for Mediterranean fruit fly (=medfly), Ceratitis capitata (Wiedemann). Major research objectives concentrate on stage five (exploration and collection of natural enemies), and stage seven (testing and selecting natural enemies for additional work). Coffee was collected monthly from three locations in Kenya from November 1997 through July 1999. Four species of tephritid flies and ten parasitoid species were recovered. Four guilds of parasitoids were recorded, and two egg-prepupal endoparasitoids, Fopius caudatus (Sz??pligeti) and F. ceratitivorus (Wharton), were discovered. The oviposition behavior of these two species is contrasted. Domination of this tropical parasitoid assemblage by koinobionts is discussed relative to the dominance of temperate fruit-infesting tephritid systems by idiobionts. Fruit handling procedures were examined for impact on overall percent emergence and specifically percent emergence of flies versus parasitoids. It was determined that stirring samples had a significant positive effect on overall emergence, however daily misting of fruit did not. The only treatment without a significant bias in fly emergence over parasitoids was the stirred/dry treatment. Effects of these results on rearing procedures are discussed. Host specificity and host suitability of parasitoids reared from coffee were examined via: (1) association of parasitoids with host flies based on characteristics of the fly puparia from which parasitoids emerged, (2) rearing of cucurbit infesting tephritids and their parasitoids in Kenya, (3) rearing of flowerhead infesting tephritids and their parasitoids in Kenya and Hawaii, and (4) host range testing of Psyttalia species in Kenya and Hawaii. These results are discussed in terms of their utility for predicting nontarget effects. Psyttalia concolor (Sz??pligeti) was shipped to Hawaii and tested against the nontarget gall forming tephritid Procecidochares utilis Stone introduced to control the weed Ageretina adenophora (Maui pamakani). Psyttalia concolor failed to attack the gall-forming P. utilis both in choice and no-choice tests, but readily attacked tephritid larvae offered in fruit in choice tests. Recommendations for further testing and release of the parasitoids from Kenya are discussed for Hawaii and Latin America.