Submitted to: Biological Control
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/28/2007
Publication Date: 10/1/2007
Citation: Garcia-Medel, D., Sivinski, J.M., Diaz-Fleischer, F., Ramirez-Romero, R., Aluja, M. 2007. Foraging behavior by six fruit fly parasitoids(Hymenoptera:Braconidae) released as single- or multiple-species cohorts in field cages: influence of fruit location and host density. Biological Control. 43:12-22. Interpretive Summary: Tephritid fruit flies are major impediments to agricultural exports wherever they occur, but the mass-release of natural enemies is an environmentally-friendly means of controlling their numbers and impact. Scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville, Florida in collaboration with colleagues at the Instituto de Ecologia (Xalapa, Veracruz, Mexico) have examined how candidate parasitoids interact so that the best combinations can be reared and released together. It was found that some species change their foraging behaviors in the presence of competitors and that it would be best to avoid such combinations during control procedures.
Technical Abstract: In nature, both native and exotic fruit fly parasitoids exhibit spatial and temporal overlaps in distribution. To better characterize the spatial component of foraging in the braconid portion of this guild, and to examine the effects of intra- and interspecific competition on resource partitioning, we conducted two field-cage experiments aimed at: 1) assessing the host-finding ability of parasitoids when single- or multiple-species cohorts were confronted with very low host-densities only at canopy level (five of 20 fruit infested with two larvae per fruit); 2) determining the height level preference (canopy vs. ground) for parasitoid foraging activity when single- or multiple-species cohorts were present and host density was high (20 infested fruit with 20 larvae each); 3) identifying candidate species for biological control programs using multiple-species releases. We studied two exotic species, Diachasmimorpha longicaudata and D. tryoni, and four native, Doryctobracon areolatus, D. crawfordi, Opius hirtus, and Utetes anastrephae (all Braconidae, Opiinae). Parasitoids were allowed to forage for 8-has single- or multiple-species cohorts in a room-sized cage containing potted trees with guavas artificially infested with Anastrepha ludens larvae and attached to the branches. When parasitoids were released as single-species cohorts into low host-density environments (fruit only at canopy level), D. longicaudata, D. tryoni and O. hirtus clearly distinguished uninfested from infested fruit and exerted the highest rates of parasitism with a significantly female-biased offspring sex ratio. When multiple-species cohorts were released, the same pattern was observed but, D. crawfordi and D. areolatus did not parasitize any larvae. In the case of the high host-density condition and with fruit at canopy and ground levels, when parasitoids were released in single-species cohorts, only D. crawfordi and D. longicaudata parasitized larvae at ground level. At canopy level, D. longicaudata, O. tryoni and D. crawfordi achieved the highest parasitism rates. When parasitoids were released as multiple-species cohorts, individuals of none of the species foraged at ground level, and in the canopy foraging activity and parasitism rates dropped dramatically in all species, except D. hirtus. Given the performance of D. hirtus, it should be considered a potential candidate to complement D. longicaudata in low-host density prevalence areas.