COMMODITY TREATMENT AND QUARANTINE ENTOMOLOGY Ionizing Radiation as a Phytosanitary Treatment Against Fruit Flies (Diptera: Tephritidae): Efficacy in Naturally Versus Artificially Infested Fruit

Some phytosanitary irradiation treatment research against tephritid fruit ßies (Diptera: Tephritidae) has used artiÞcially infested fruit with the unstated and untested assumption that the method adequately simulated a natural situation. We compare grapefruit, Citrus paradisiMacfayden, naturally infested byMexican fruit ßy,Anastrepha ludens (Loew), via oviposition until larvae reached the late third instar versus insertion of diet-reared third instars into holes made in grapefruits 24 h before irradiation; the latter technique has been used in other studies. Both infestation techniques resulted in statistically indistinguishable results, indicating that insertion of diet-reared third instar Mexican fruit ßy intoholesbored intograpefruit and subsequently sealed24hbefore irradiationwould adequately represent natural infestation and could be used to develop a radiation phytosanitary treatment of the insect in grapefruit when prevention of adult emergence is used as the measure of efÞcacy. Nevertheless, it may not be advisable to extend this conclusion to other fruit ßy/fruit combinationswithout doing appropriate comparison studies.Dissectionof puparia fromnonirradiated control insects that failed to emerge as adults showed a relatively even distribution ofmortality among the developmental stages within the puparium. In contrast, dissection of puparia from irradiated third instars that did not emerge as adults revealed a sharp attenuation in development from cryptocephalic to phanerocephalic pupae demonstrating this transition to be the developmental step most affected by radiation.