Density of pheromone sources of the weaver ant Oecophylla longinoda affects oviposition behaviour and damage by mango fruit flies (Diptera:Tephritidae)

As damage by the fruit flies Bactrocera invadens and Ceratitis cosyra is significantly reduced in mango trees with weaver ants, but we rarely observed adult flies being captured, we investigated whether Oecophylla pheromones affect fruit fly oviposition behaviour. Mangoes were collected within 1 m and 1-3 m distance from ant nests, and from ant-free trees. Using both choice and no-choice tests, fruit flies were allowed to oviposit on fruits for 72 h in the absence of ants. Flies landed significantly more and spent more time on fruit from ant-free than from ant-colonized trees. The density of ant pheromone sources significantly affected the oviposition time and the number of fruit fly pupae collected per kg fruit under greenhouse conditions. However, field data did not show any difference in damage for fruit collected within 1 m and 1-3 m distance from ant nests, suggesting that physical or visual mechanisms complement the repellencey effect of ant pheromones against fruit flies. (Résumé d'auteur