Bait stations are widely used to control Ceratitis capitata, even though the effect of intrusion from untreated areas decreases the efficacy of the technique. In this work, the edge effect of outer fruit fly populations from untreated areas and backyard orchards has been studied. For this purpose, a field trial was carried out during four years in a wide area of 10 000 ha located in Valencia (Spain). The main growing species were Prunus persica, Prunus domestica, Citrus sinensis, Citrus reticulata and Diospyros kaki. An area of 3,600 ha was treated with chemosterilant bait stations. Fruit fly populations were monitored during the 4 years of study inside and outside the treated area using Tephri-traps baited with trimedlure. A grid of 180 t...