Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/1998
Publication Date: N/A
Interpretive Summary: Tephritid fruit flies consume scores of species of fruits and vegetables and because of quarantines restrict the development of agricultural exports around the world. Biological control, the introduction or augmentation of natural enemies, offers a means to control pest species but little is known of the distributions and behaviors of fruit fly natural enemies. Such knowledge is important when considering which natural enemies might be best suited for a particular environment. In Florida, two parasitoids of the Caribbean fruit fly were originally introduced into the same locations but over time they have come to inhabit different regions of the state. This geographic difference may be due to competition for hosts on a smaller scale; i.e., their manner of searching for hosts might overlap to such an extent that each species is forced from areas where it could survive if alone and driven into citadel-regions where the environment is slightly more advantageous for one species or the other. In those rare locations where both species cooccur there is an extreme overlap in the parts of fruit trees where each parasitoid is found as well overlaps in their preferences for fruit sizes and other aspects of the tree canopy. This suggests that competition between the two species is intense. Further work may discover other natural enemies could be introduced to attack flies not exploited by these two very similar species.
Technical Abstract: In the area of LaBelle, Florida (Hendry County), the Caribbean fruit fly, Anastrepha suspensa (Loew), is commonly attacked by two braconid parasitoids, Doryctobracon areolatus (Szepligeti) and Diachasmimorpha longicaudata (Ashmead). Knowledge of the distributions within tree canopies of the pest-fly, and of its natural enemies, may lead to improvements in its biological control. Fruits from thirteen individual trees of four species were systematically sampled. Uninfested fruit were heavier than infested ones in four of five significant instances. This may be due to the presence of the larvae. There was little evidence that A. suspensa prefers to oviposit in a particular microhabitat. In two of two significant cases uninfested fruits were lower in the canopy than infested fruits, and in two of three significant cases uninfested fruits were closer to the canopy margins. Differences in the distributions of the two parasitoids, mean size of fruits containing parasitoids and mean distance of these fruits from canopy margin, were only found in Cattley guava shrubs, Psidium cattleianum Sabine. In two instances, D. longicaudata was relatively more abundant on the margins of canopies. In one instance D. areolatus occurred in significantly heavier fruits. Niche similarity in the two parasitoids may be due to the absence of a shared evolutionary history. Both are recent introductions to Florida, but while D. areolatus is a neotropical species D. longicaudata is from the Indo-Philippine region. Thus, there has been little opportunity for divergence.