Ernest J. Harris

The fruit fly parasitoid Fopius arisanus: reproductive attributes of pre-released females and the use of added sugar as a potential food supplement in the field

Fopius (= Biosteres) arisanus (Sonan) (=Opius oophilus Fullaway) (Hymenoptera: Braconidae) is an egg‐pupal parasitoid of tephritid fruit flies. Small scale releases of F. arisanus were undertaken in coffee, Coffea arabica L., on the island of Kauai, to evaluate its potential for suppression of fruit fly populations. In conjunction with field releases, assays were conducted to determine the quality of pre‐released parasitoids. In addition, the suitability of various sugars as potential food supplements in the field was evaluated. Spermathecal dissection showed that >70% of a total 1.7 million females released in 1998 and 1999 were successfully mated. Moreover, a sperm rating of 2.5–2.6 indicated that the spermathecae of inseminated females were 50% full. There were 85–137 matured eggs (mean = 101.7 ± 11.5) in the ovaries of mated or virgin females. When honey was replaced with ripe coffee and water, ripe coffee, or water alone, 10 days after emergence, females remained alive for another 5.5, 5.4, and 4.9 days, respectively. There was corresponding deterioration in the ovaries of gravid females. Mean eggs of honey‐deprived females declined from >100 to <70 shortly before their death. Suitability test of various sugars showed that females lived longer when fed with honey (26 days), maple syrup (25 days) or molasses (20 days). Moreover, females provided with these sugars produced mean cumulative progeny per female of 77.2 ± 19, 67 ± 7, and 81 ± 14, respectively, during a 2‐week egging period. Our findings provided a basis for development of field release strategy for F. arisanus.

Suppression of melon fly (Diptera: Tephritidae) populations with releases of Fopius arisanus and Psyttalia fletcheri (Hymenoptera: Braconidae) in North Shore Oahu, HI, USA

Field experiments and surveys were conducted to evaluate the efficacy of releasing Fopius arisanus (Sonan) and Psyttalia fletcheri (Silvestri) parasitoids for suppression of Bactrocera cucurbitae (Coquillett) infesting wild Coccinia grandis L. In 2003 and 2004, P. fletcheri releases combined with natural emergence from wild fly populations resulted in better fly suppression, compared to the control site. While P. fletcheri developed freely on melon fly, F. arisanus was less successful at producing its own progeny, yet causing mortality and a twofold decrease in pupae recovered from ivy gourds. Concurrent releases of both parasitoids exerted a compounded suppressive effect on the melon fly population 2–3 times higher than during the pre-release phase. A similar, less obvious, pattern occurred in 2004, due to reduction of the ivy gourd fruit canopy. In 2005, only P. fletcheri was released, with greatly reduced impact, due to ivy gourd destruction and by growers leaving crop culls in fields, producing large numbers of melon flies unaffected by parasitoid releases.

Demography of a native strain of the melon fly, Dacus cucurbitae, from Hawaii

Preadult development and survival rates for a wild strain of melon fly in Hawaii were examined when reared on six common hosts at 25 °C. These data were combined with information gathered on adult survival, fecundity and fertility in order to construct life tables.

Irradiation of Anastrepha ludens (Diptera: Tephritidae) eggs for the rearing of the fruit fly parasitoids, Fopius arisanus and Diachasmimorpha longicaudata (Hymenoptera: Braconidae)

Abstract Irradiated eggs of Anastrepha ludens were evaluated as hosts of two fruit-fly parasitoids for mass rearing. Three different ages of A. ludens eggs (24-, 48- and 72-h-old) were analyzed for hatchability after being subjected to radiation doses of 2.5, 5, 7.5, 10, 12.5, 15, 17.5, 20, 22.5, 25, 27.5 and 30 Gy. No significant reduction in hatchability occurred with the 72-h-old eggs at any of the radiation dose levels and no adult emergence occurred at radiation doses greater than 25 Gy. Seventy two-h-old eggs irradiated above 25 Gy were found to be the best age and dose for fruit fly egg hosts to be used in mass rearing the egg parasitoid Fopius arisanus. It was demonstrated that larvae hatching from the irradiated A. ludens eggs can also be used as hosts for Diachasmimorpha longicaudata. Parasitoid emergence of both species was not statistically different from the control group (parasitoids emerged from non-irradiated host). The fecundity of parasitoids emerged from irradiated hosts also was similar to that obtained with parasitoids reared with non-irradiated hosts. There were some statistical differences between the curves for longevity. However, these were not clearly correlated with radiation dose. The results of this study will aid in the design of improved methods for mass rearing and release of fruit-fly parasitoids.

Effects of depth of oviposition dish and age ofrearing host on efficiency of mass production of thetephritid fruit fly parasitoid Psyttaliafletcheri

Psyttalia fletcheri is a solitary larval endoparasitoid ofthe melon fruit fly, Bactrocera cucurbitae. Initiallycolonized in 1985, mass production of P.fletcheri for the last 10 years has beenfacilitated with a rearing method developed earlier.However, the level of parasitoid recovery seldomexceeded 35%. We examined the parasitoidsdevelopmental biology and behavior to identify theprocedures that may improve efficiency ofproduction. We found that by limiting the depth ofoviposition dish (receptacle that holds the hostlarvae during exposure to female parasitoids) to 4 mm and using 4-d-old (late 2nd instar) B.cucurbitae larvae for oviposition, parasitoid yieldwas increased two-fold.

Biological attributes of three introduced parasitoids as natural enemies of fruit flies, genus Anastrepha (Diptera: Tephritidae)

The biological attributes of three introduced species of parasitoids which attack the fruit fly Anastrepha ludens were evaluated. Larvae and eggs of A. ludens were exposed to larval parasitoids Diachasmimorpha longicaudata and D. tryoni and the egg parasitoid Fopius arisanus. Parasitoid longevity and fecundity were determined using larvae and eggs of A. ludens. Likewise, the parasitism rates of these parasitoid species in infested host fruits were recorded. The intrinsic rate of increase for F. arisanus was 0.1019 followed by D. tryoni with a rate of 0.1641 and D. longicaudata with the highest rate of 0.2233. Although F. arisanus females had the highest levels of fecundity, only 50% of them remained alive until reproductive age. These results in combination with the longer generation time (in comparison with D. longicaudata and D. tryoni), can be considered as the most important factors explaining F. arisanus reduced rate of increase. However, we note that oviposition activity caused egg mortality which reduced Anastrepha egg hatch by ca. 20%. This result suggests that F. arisanus has a high potential as a natural enemy of A. ludens, in accordance with our research efforts to develop a new F. arisanus strain specialized for development in Anastrepha eggs. The results show that D. tryoni is not a good candidate for biological control of Anastrepha. Meanwhile, D. longicaudata continues to be the most important exotic parasitoid for suppression of Anastrepha fruit fly populations.