Interspecific Interactions and Host Preference of Anastrepha obliqua and Ceratitis capitata (Diptera: Tephritidae), Two Pests of Mango in Central America

The larvae of Anastrepha obliqua L. and Ceratitis capitata Wied. (Diptera; Tephritidae) destroy mango fruits (Jir6n & Hedstrom, 1988), while fruit flies of the genus Anastrepha, (including A. obliqua, A. ludens, and A. striata) cause extensive damage to a large variety of Neotropical commercial and wild fruit hosts (Norrbom & Kim, 1988). A. obliqua has been found on fruits in the Anacardiaceae, frequently in hog plums (Spondias spp.) and mangos (Jir6n 1995). This species of fly began to attack mango extensively as a host when mangos were introduced into tropical America during the 18th century (Jir6n 1995). In the past, C. capitata was found only in Africa and the Mediterranean basin, but in the 1950's, it was accidentally introduced to the Western Hemisphere (Jir6n & Salas 1992). In these new areas, it occurs in a wide variety of habitats with a large number of host species (such as Citrus and Terminalia catappa) (Nishida et al. 1985). A. obliqua oviposits in a few plant species belonging predominantly to the Anacardiaceae, while C. capitata attacks numerous fruit species belonging to different families (Jir6n et. al. 1988). Studies by Salas (1958), Christenson & Foote (1960), and Jir6n & Zeledon (1979) suggest that species of Anastrepha compete with an opportunistic C. capitata for fruits on which to oviposit. Castillo (1987) observed that Anastrepha striata adults attacked adult C. capitata and displaced them from a guava fruit. On mango, 94% of infested fruit contained A. obliqua and 6% contained C. capitata (Jir6n & Hedstrom 1988). Interspecific interactions of adults on mango were examined by placing 30 females of each species, A. obliqua and C. capitata, in a 30 x 30 x 30 cm screen cage with a nearly ripe mango fruit placed on the middle of the floor. Adults ofA. obliqua were obtained from colonies maintained in the mass rearing laboratory at the Estacion Experimental Fabio Baudrit, Alajuela, Costa Rica. C. capitata adults and their diet were supplied by H. Camacho, Escuela de Biologia, Universidad de Costa Rica. The following data on the behavior of the flies were taken: 1) incidence of A. obliqua displacing C. capitata from the fruit, 2) incidence of C. capitata displacingA. obliqua from the fruit, and 3) incidence of both species occurring on the same fruit with no interaction. The flies were observed for 30 min for each trial. Each trial was replicated four times. The outside of the cage screen was moistened by wiping the screen with a wet sponge. This procedure kept the humidity within the cage relatively high. The flies were observed for four repetitions of 30 min each. Host fruit preference tests with nearly ripe mangos and ripe oranges were done by placing fifteen females of each species in a 30 x 30 x 30 cm screen cage. Three mangos,