Effect of Diachasmimorpha tryoni on two non-target flowerhead-feeding tephritids

Laboratory tests were conducted to evaluate the possible effect of a delibe rately introduced fruit fly parasitoid, Diachasmimorpha tryoni, on 2 non-ta rget flowerhead-feeding tephritid flies, Trupanea dubautiae and Ensina sonc hi. The former is an endemic Hawaiian tephritid which feeds on flowerheads of the native composite shrub, Dubautia raillardioides; the latter is an in advertently introduced tephritid infesting flowerheads of the exotic weed, Sonchus oleraceus. Gravid females of D. tryoni were confined in test cages with field-collected D. raillardioides and S. oleraceus flowerheads infeste d with late instars of T. dubautiae and E. sonchi, respectively. D. tryoni showed low levels of visiting and probing responses to D. raillardioides fl owerheads and relatively higher responses to S. oleraceus flowerheads in bo th the presence and absence of the parasitoid's normal host, the Mediterran ean fruit fly, Ceratitis capitata. With 72-h exposure to D. tryoni, 13.9 an d 2.6% of T. dubautiae were attacked by test parasitoids in the absence and presence of C. capitata in the test cage, respectively; while 56.8 and 34. 2% of E. sonchi were attacked. In contrast, 94.0 and 84.0% of C. capitata l arvae presented in screened dishes with diet in test cages were attacked by D. tryoni in tests with T. dubautiae and E. sonchi, respectively. Attack o f D. tryoni on flowerhead-feeding T. dubautiae and E. sonchi resulted in si gnificant reduction in the emergence of adult flies, especially in the abse nce of the parasitoid's normal host. While 8.8-12.8 adult D. tryoni per tes t (both males and females) successfully emerged from medflies, no adult D. tryoni progeny emerged from T. dubautiae, and only 3 deformed males of D. t ryoni (much smaller than the normal wasp) emerged from E. sonchi. The relev ance of these findings to the safety of future biological control programs against tephritid pests is discussed.