Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/1997
Publication Date: N/A
Citation: Interpretive Summary: Fruit flies both destroy crops and, because of quarantines, hinder trade and economic growth throughout the tropics and subtropics. There is an increasing interest in releasing the natural enemies of pest fruit flies in the USA and elsewhere, either to become established in the wild or as mass-reared "biological-insecticides". However, very little is known about these parasitoids; where they hunt and rest, what flies they prefer, what times of the year they are most active and whether they interfere with each other as they forage for hosts. Entomologists from the USDA-ARS in collaboration with Mexican colleagues studied five species of parasitoids in the field. In this paper they look at how effective natural enemies are at various times and places within fruit tree canopies. It is hoped that a knowledge of these parasitoids will help plan introductions of natural enemies into the places that suit them the best.
Technical Abstract: In Veracruz State, Mexico the temporal and spatial distributions of 5 species of parasitic Hymenoptera attacking larvae of 5 species of Anastrepha in 7 species of fruit tree canopies were examined. The parasitoids are abbreviated as follows: Doryctobracon areolatus (Szepligeti) (Braconidae)=Da; D. crawfordi (Viereck)=Dc; Diachasmimorpha longicaudata (Ashmead) (Braconidae)=Dl; Utetes anastrephae (Viereck) (Braconidae)=Ua; Aganaspis pelleranoi (Brethes) (Eucoilidae)=Ap. Parasitism by Da, Dl and Ua was higher in 3 of 4 significant cases in the lower portions of the canopies. Ua was more abundant in the interior of canopies (2 cases), while Da was more common in the margins (1 case). The mean size of fruits containing parasitoids was smaller than that of infested fruits without parasitoids. Ua attacked larvae in a relatively narrow range of smaller host species. Dl may be better able to locate and/or attack hosts in larger fruits. There were on average more host pupae in fruits containing parasitoids than in fruits without parasitoids. Parasitism by Da, Dc, Dl and Ua often changed over time during the fruiting period, sometimes seasonally. There were only a few instances of significant relationships between parasitism and local differences in the canopy in terms of fruit numbers, host numbers and host density. Changes in the relative numbers of Da and Ua suggest interspecific competition. Information on the distribution of parasitoids at levels ranging from within canopies to across regions may guide biological control efforts, allowing the match of candidate species to locations.