Progress towards trail pheromone disruption in Argentine ants (Linepithema humile)

The first application of ant trail pheromones as a control tactic is under development, using Argentine ant as the model target. Both laboratory and field studies are needed to accomplish this challenging goal, in order to understand the conditions required for success. Whether reduced foraging by reduction in food supply will be enough to suppress field populations remains to be seen. However, an excess of trail pheromone has recently been demonstrated to disrupt trails in the laboratory and to reduce the incidence of trails and foraging rates in the field as long as (Z)-9-hexadecanal is continuously released. Little is known of the concentrations required for success. We hypothesized that higher disruptive pheromone quantities would be needed for higher ant populations, as seen for moths. We laid a trail of synthetic (Z)-9-hexadecanal on a glass surface at two rates, and we laid a second shorter trail near the middle of the first trail, but 1.5 cm upwind. We found that disruption of trails required 100 fold more pheromone upwind before disruption could be achieved, independent of base trail concentration. This implies that in the field, trail disruption will be less successful when high ant trail densities are present but more successful against newly formed or weak trails. It is not yet clear whether high traffic rate trails can form in a disrupted area and more field tests are needed. The development of suitable formulations will encourage this.