Responses of Anastrepha fraterculus and Ceratitis capitata to infested fruit

ALEJANDRO G. PIETREK; DIEGO F. SEGURA; MARÍA C. LIENDO; MARÍA T. VERA; MARIANA M. VISCARRET; FRANCISCO DEVESCOVI; JORGE L. CLADERA

Salvador de Bahia, Brasil.

Congreso; 7th International Symposium on Fruit Flies of Economic Importance.; 2006

Anastrepha fraterculus and Ceratitis capitata are major pests in Argentina, overlapping in most of their ecological requirements. But, do they compete? In C. capitata , laboratory studies previously demonstrated that females recognize egg infestation by the presence of a host marking pheromone (HMP), but little is known about A. fraterculus responses to a fruit previously infested by a con-specific. We set to study the recognition of host infestation, intra-specific as well as inter-specific. We placed a green pepper transversally cut in an acrylic cage (20 cm x 20 cm x 20 cm) and during 40 minutes we recorded the following behavioral variables for gravid females of both species: landing on fruit, time of permanence in the fruit, punctures performed to the fruit and duration of oviposition. We compared eight treatments performing nearly 30 repetitions of each. We offered: fruit previously infested with C. capitata egg to C. capitata, prior C. capitata egg infested fruit without HMP to C. capitata, prior A. fraterculus egg infested fruit to C. capitata, clean fruit to C. capitata, prior A. fraterculus egg infested fruit to A. fraterculus, prior A. fraterculus egg infested fruit without HMP to A. fraterculus, prior C. capitata egg infested fruit to A. fraterculus, and clean fruit to A. fraterculus.  Individuals of A. fraterculus landed on clean fruit twice as often as on infested fruit, regardless of the presence of marking pheromone. On the contrary, C. capitata exhibit no differences in fruit landing among treatments. For the latter species, we found that individuals punctured more frequently on clean fruit than on infested fruit. Also, oviposition duration (which is a good indicator of clutch size) was longer when clean fruit was the substrate. Inter-specific responses showed an interesting pattern. On the one hand, A. fraterculus landed less frequently on peppers when they were infested by C. capitata showing no difference between con-specific and inter-specific egg infestation response. On the other, oviposition duration in C. capitata decreased with egg infestation in a comparable way either infested by A. fraterculus or infested by conspecifics. Our results suggest that these fruit flies respond to signals of fruit infestation, other than host marking pheromone and that the recognition of infestation occurs in A. fraterculus at a different level than in C. capitata. Additionally inter-specific recognition of infestation was evident here for both species. This mechanism would avoid inter-specific competition and promote the coexistence of these two pests.