The use of alarm pheromones to enhance bait harvest by grass-cutting ants

Abstract

The enhancement of bait for the control of grass-cutting ants was investigated using two species of grass-cutting ant, Atta bisphaerica (Forel) and Atta capiguara (Gonçalves) (Hymenoptera: Formicidae). Bait was applied in loose piles to obtain a direct relationship between ant attraction and bait harvest. Enhancement with alarm pheromone compounds significantly increased the attractiveness and harvest of bait under certain conditions. A large proportion of the ants attracted to the enhanced bait were minor workers. These ants rarely transport bait because of their small size, and so it may be possible to increase the effect of bait enhancement by using smaller bait granules. Foragers of A. capiguara were less inclined to transport citrus-pulp bait than were those of Atta laevigata (Fr. Smith), a species that also harvests dicotyledonous plants. This emphasizes the importance of developing a bait matrix that is more acceptable to grass-cutting species. Nevertheless, the results suggest that alarm pheromone compounds have significant potential to improve the efficacy of baits for the control of grass-cutting ants.