Anastrepha fraterculus (Wiedemann), the South American fruit fly, and Ceratitis capitata (Wiedemann), the Mediterranean fruit fly, are the only economically important Tephritidae species present in the citrus-growing areas in the province of Corrientes, northeastern Argentina. Both fruit fly species severely limit the export of fruit because of quarantine restrictions in importing countries. In this Argentinean region, C. capitata has been reported mostly infesting cultivated Citrus species such as C. sinensis L. (Osbeck) (Rutaceae) and C. paradisi Macfadyn (Rutaceae), whereas A. fraterculus has been found almost exclusively in wild guava (Psidium guajava L. (Myrtaceae)), a wild host plant (Turica and Mallo 1961).