Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2007
Publication Date: N/A
Interpretive Summary: Fruit flies, such as the Mediterranean, Caribbean and Mexican fruit flies, attack hundreds of fruits and vegetables, but can be suppressed through the release of mass-reared parasitoids. However, the expense of rearing these natural enemies is sometimes prohibitive. Scientists at the USDA-ARS Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida in collaboration with APHIS and Mexican colleagues examined the possibility of sequentially exposing fruit fly hosts to two different parasitoids. Those flies that had escaped attack from the first species would be parasitized by the second thus maximizing the use of the hosts. Among the combinations of examined species, the summed number of sequentially reared parasitoids was no greater than those that resulted from exposures to single species. New combinations will be tested as different parasitoids become available.
Technical Abstract: A series of evaluations were carried out to assess the feasibility of sequentially exposing tephritid hosts to two different parasitoid species, thus allowing unparasitized flies to be attacked and optimizing the production in natural enemy mass-rearing programs. Larvae or pupae of Anastrepha ludens (Loew) were exposed either to no parasitoids, the larval parasitoid Diachasmimorpha longicaudata (Ashmead) (primary parasitoid), the pupal parasitoids Coptera haywardi (Oglobin), Dirhinus sp., and Eurytoma sivinski (Gates and Grissell) (secondary parasitoids), or sequentially to combinations of both the larval and pupal parasitoids. As part of all evaluations, host larvae were either irradiated or unirradiated. Under the conditions tested, a second host exposure did not increase parasitoid production. The main problem was a high incidence of mortality due to multiparasitism. With the exception of pupae exposed to C. haywardi, obtained from irradiated larvae previously exposed to D. longicaudata, the percent multiparasitism was around 50 %. This resulted in a reduction in emergence of both parasitoids. To some extent, pupal parasitoids discriminated among pupae, preferring to oviposit in pupae that were not superparasitised previously by D. longicaudata. Pupae resulting from irradiated larvae were not appropriate for the development of C. haywardi. In Dirhinus sp. and E. sivinski pupal development was obtained in irradiated larvae, although emergence was significantly lower than in unirradiated larvae. These findings offer possible alternatives to fine-tuning the use of sequential host exposure to maximise parasitoid production.