Occurrence of diapause in neotropical parasitoids attacking Anastrepha fraterculus (Diptera: Tephritidae) in a subtropical rainforest from Argentina.

Abstract

Incidence of diapause in neotropical parasitoid species associated with the tephritid fruit fly Anastrepha fraterculus (Wiedemann) infesting three major host plants collected from the southernmost end of Argentinean Yungas rainforest was studied. Three other objectives were the frequency of diapause according to the fruiting season of Prunus persica (L.) Batsch (peach), Psidium guajava L. (guava) and Juglans australis Grisebach (walnut); the length of diapause period for each recovered parasitoid species; and the proportion of diapausing parasitoid individuals that displayed prolonged diapause. Between 2001 and 2003, infested ripe fruits were weekly collected in wild vegetation areas. A portion of the fruit samples was processed at the same collection site. Recovered A. fraterculus puparia were kept under natural environmental conditions inside a wooden frame cage covered with a cloth mesh. The remaining halves of fruit samples were taken to the laboratory and puparia were kept under environmental controlled condition. Unenclosed puparia were kept for 2 years. Diapause period fluctuated between 131 and 426 days and was observed in all recovered parasitoid species (Doryctobracon areolatus (Szépligeti), D. brasiliensis (Szépligeti), Opius bellus Gahan, Utetes anastrephae (Viereck) and Aganaspis pelleranoi (Brèthes)). All diapausing individuals dissected from host puparia were instar III and were also remarkably different from non-diapausing larvae because of their smaller body size. The 65% of all diapausing individuals was recorded in early autumn and was recovered from A. fraterculus larvae that had developed in guava. Prolonged diapause was recorded in a small fraction of the diapausing populations of D. brasiliensis, D. areolatus and A. pelleranoi. Results suggest that diapause is an adaptive mechanism that allows parasitoids to overcome periods of marked host scarcity given that guava is the last widely available host plant before the winter season begins.