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item Thomas, Donald

Submitted to: Neotropical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2003
Publication Date: 7/10/2003
Citation: Thomas, D.B. 2003. Reproductive phenology of the mexican fruit fly in the sierra madre oriental. Neotropical Entomology. 32:385-397.

Interpretive Summary: The Mexican fruit fly is native to the Sierra Madre of northeastern Mexico where it breeds on wild citrus. When commercial citrus (oranges and grapefruit) were introduced into the region at the foot of the mountains, the insect naturally began to infest the orchard fruit and became a major pest in Mexico. For reasons that are not entirely clear, this insect is captured periodically in Texas, but soon disappears. Its presence in the citrus growing region of Texas triggers quarantine restrictions even though it has never been found infesting commercial fruit here. In order to understand the population dynamics of this pest, studies were undertaken where the populations are established year round. In particular, the reproductive cycle of the Mexfly was examined in its native habitat in order to understand why the populations peak in different years and at certain times of the year. Large populations are associated with mild winters. Fly activity is lowest in the summer and in the winter. The crop of wild citrus fruit in the springtime produces large numbers of flies. A second peak in fly numbers occurs in the fall, suggesting that there are normally two generations per year, one in the spring and one in the fall.

Technical Abstract: In its native habitat in northern Mexico, Anastrepha ludens (Loew) is normally bivoltine although a third generation is achieved in some years. The flies overwinter mainly in the puparial stage, emerging in January-February. These flies oviposit in the spring crop of a wild citrus, Sargentia greggi (Wats). The primary population peak follows in late spring to early summer (in exceptional years, separate peaks in spring and summer). Dissection of the females demonstrated that most of the flies in the spring peak are reproductively immature, indicating emergence of new adults. Activity subsides in late summer, or at least, few flies can be trapped at this time. Then in the fall, there is a resurgence of adult activity. However, in contrast to the spring peak, dissection revealed that the great majority of the fall adult females are already gravid, indicating that they are carry-overs from the early summer population, rather than new recruits. The fall adults oviposit in October-November, producing the overwintering population that will emerge as adults in January-February.