DEVELOPMENT OF QUARANTINE ALTERNATIVES FOR SUBTROPICAL FRUIT AND VEGETABLE PESTS
Title: Grapefruit as a host for the West Indian fruit fly (Diptera: Tephritidae)
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 23, 2009
Publication Date: February 1, 2011
Citation: Mangan, R.L., Thomas, D.B., Tarshis Moreno, A.M., Robacker, D.C. 2011. Grapefruit as a host for the West Indian fruit fly (Diptera: Tephritidae). Journal of Economic Entomology. 104(1):54-62.
Interpretive Summary: When a specific commodity is shown to be a non-host for a quarantined pest species, market access and trade are not affected by quarantine restrictions by presence of that pest. The West Indian fruit fly has historically been listed as a pest of citrus, but a number of changes in taxonomy, misidentification and lack of documentation, have made this relationship questionable. A review of literature is provided here that shows that confusion in the identifications, changes of fruit fly species names, and repeated citations of questionable identifications, may have confused the host status for this pest. Experiments were performed using methods that were accepted in other host status studies and a new system is proposed and tested. Experiments using forced cage infestation showed that grapefruit allowed only occasional survivors of West Indian fruit flies to pupation, while the Mexican fruit fly was more than 50 times more successful. A new approach that traces survival of eggs to produce larvae and larvae in the 3 tissues (flavedo, albedo and pulp) showed that eggs of the West Indian fruit fly were not inserted below the flavedo and about half of the eggs were exposed at the fruit surface. Most mortality of both West Indian and Mexican fruit fly occurred in the albedo. Survivorship of both species improved as later season fruit were tested. Over all of the tests, survival of West Indian fruit fly resulted in only occasional survivors, while Mexican fruit fly survival in late season fruit (April and May), was more than 50-100 times higher.
The most common hosts for the West Indian fruit fly, Anastrepha oblique (Macquart), are fruits of the family Anacardiaceae (mangos and mombin species). However, similar to many of the tropical fruit flies of major economic importance, this species attacks several other families of crop fruit, including Annonaceae (cherimoya), Myrtaceae (guava), Oxalidaceae (carambola), Passifloraceae (granadilla), and Sapotaceae (mamey sapote). In the family Rutaceae, the economically important genus Citrus has been reported and until recently, considered a host for this fruit fly. Our review of the literature shows a great deal of confusion concerning the taxonomy of this species, including synonomies and confusion with other species. The deterrent effects of the flavenoids, naringin and narigenin for oviposition, while significant, were not absolute. Tests were carried out under laboratory conditions with both fruit on the tree and harvested fruit that showed that 15-40 times greater survival of the Mexican fruit fly, Anastrepha ludens (Lowe), (whose preferred hosts include Rutaceae) on grapefruit compared to the West Indian fruit fly, for both tree attached and picked fruit. Tests of survival of developing stages over time showed that the two species oviposit into different tissues in the fruit, that both have high mortality in early season fruit, and that mortality is much higher for the West Indian fruit fly in the flavedo and albedo of the fruit compared to the Mexican fruit fly. These results support the decision by USDA-APHIS to remove the West Indian fruit fly from the list of quarantine insects for grapefruit.