Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/1997
Publication Date: N/A
Interpretive Summary: Parasitoids play an important role in lowering the numbers of pest fruit flies. In addition to being released to hunt and kill fruit flies on their own, they are sometimes mass reared and released "augmentatively". In Florida augmented releases of the parasitoid Diachasmimorpha longicaudata help protect fly free zones from the Caribbean fruit fly. However, there are other natural enemies that could be used. Little is known of their geographic range or environmental tolerances. One candidate is another parasitoid, Doryctobracon areolatus. It also occurs in Florida. USDA/ARS scientists in cooperation with Mexican colleagues at the Instituto de Ecologia found that in an area where the 2 species occur together D. longicaudata is most common late in the fruiting periods of fruit trees, and that climate, temperature and humidity was the factor most likely to be responsible. Knowing which parasitoids are best suited to a particular area or time of year may allow augmented releases to be tailored to local conditions.
Technical Abstract: Two species of Braconidae, Diachasmimorpha longicaudata (Ashmead)(=Dl) and Doryctobracon areolatus (Szepligeti) (=Da), commonly attack the Caribbean fruit fly, Anastrepha suspensa (Loew), in central Florida. In this area of co-occurrence, there are temporal changes in the relative abundance of the parasitoids. In a focal study tree, Dl becomes more abundant, actually and relatively, as the fruiting period progresses. Three hypotheses are examined, using data from the focal and other local host trees, for their ability to account for these trends. 1) Da may be superior to Dl in finding host patches, but is inferior at exploiting hosts: "Counter - balanced competition" fails to be supported in one of 5 fly-host plant species, the small fruited citrus, calamundin. In calamundin Dl becomes less abundant relative to Da through the autumn fruiting period. 2) Within-tree changes in fruit density, size or infestation levels over time can account for the ratio of Dl to Da: There is no evidence to implicate changes in hosts over time to relative rates of parasitism. 3) Seasonal changes in environment favor one species over the other: In general, Dl becomes more abundant during the spring and declines in the fall. This seasonal pattern is closely correlated to factors such as mean high and low temperatures. Climate, or some unknown biotic correlate(s), best explains the fluctuations in relative abundance. Dl is used in augmented releases to protect fly-free citrus producing zones. Information on the environmental tolerances of this and alternative parasitoids may allow future releases to be tailored to local conditions.