Field evaluation of potential of alarm pheromone compounds to enhance baits for control of grass-cutting ants (Hymenoptera: Formicidae)

Leaf-cutting ants are important economic pests of the Neotropics, and the most common method of control involves the use of insecticidal baits. Baits that are currently available exhibit low attractiveness to grass-cutting species, thus there is a need to develop improved baits. The potential for using alarm pheromone compounds to enhance the attractiveness and subsequent harvest of baits was examined for two economically important species of grass-cutting ant, Atta bisphaerica (Forel) and Atta capiguara (Goncalves). Compounds of the alarm pheromone were applied to rubber septa that were then sealed inside plastic sachets together with citrus pulp-based bait. The best candidate compound for bait enhancement was 4-methyl-3-heptanone. This compound significantly increased the attractiveness of bait sachets to both species. It also appeared to improve the discovery of nearby unenhanced sachets. However, 4-methyl-3-heptanone resulted in only a slight and non-significant improvement in bait harvest. Enhanced and unenhanced bait sachets were applied at a number of positions to obtain an improvement in harvest, but without success. The possible reasons for the lack of an enhancement of harvest and the potential for using alarm pheromone compounds as leaf-cutting ant bait enhancers are discussed.