Is the Oriental Fruit Fly (Diptera: Tephritidae) a Natural Host for the Opiine Parasitoid Diachasmimorpha tryoni (Hymenoptera: Braconidae)?

Abstract

Laboratory and field experiments were conducted to determine the suitability of the oriental fruit fly, Bactrocera dorsalis (Hendel), for the development of Diachasmimorpha tryoni (Cameron). In the laboratory, parasitism of individual B. dorsalis larvae by 6–10 D. tryoni eggs killed and prevented the pupation of 8.0 ± 3.7% of the parasitized hosts and the emergence of 50.0 ± 7.1% of the puparia. Mortality of immature B. dorsalis increased significantly as the rate of superparasitism increased. A mean of 68.0 ± 6.6% of B. dorsalis that received 1–5 D. tryoni eggs per larva pupated and eclosed to morphologically normal flies. These flies contained melanized eggs of the parasitoid in their abdomens. In uneclosed hosts which received 6–10 parasitoid eggs per larva, melanized eggs along with 1–6 melanized first-instar parasitoids were recorded. Parasitism of B. dorsalis by D. tryoni alone never results in parasitoid development beyond the first instar. However, in a heterospecific parasitism test involving D. tryoni and Diachasmimorpha longicaudata (Ashmead), ≈1/10 of the parasitized puparia eclosed to adult D. tryoni . Average percentage of D. tryoni females emerging from such neutralized B. dorsalis (parasitized by D. longicaudata before or after exposure to D. tryoni to block host immunity) was 81 to 92%. Emergence of D. tryoni from field collected B. dorsalis was also very low (0.35% emergence; 8 D. tryoni adults out of 2,279 B. dorsalis puparia). We conclude that contrary to the published host-range lists, neither laboratory-reared nor wild B. dorsalis are natural hosts for the opiine parasitoid D. tryoni .