Comparison of Argentine ant Linepithema humile (Hymenoptera: Formicidae) recruitment to hydrogel baits and other food sources

Hydrogel baits are composed of an insecticide and sugar water solution that is sustained by a super-absorbent polymer. This novel bait formulation has been increasingly used for controlling invasive ant species, as they prefer liquid foods and bait stations, which can be both costly and wasteful, are not required. Despite usage trends, the preference of invasive ants for hydrogel baits when compared with other food sources has not yet been widely demonstrated. This study evaluated the recruitment of the invasive Argentine ant Linepithema humile (Mayr) to various food sources, including hydrogel bait formulations containing sugar and insecticides (thiamethoxam, clothianidin), sugar water, tap water, a commercial paste-type fipronil bait, and a shrimp-flavored snack. The hydrogel baits and sugar water had equal recruitment levels for L. humile, irrespective of the sugar and insecticide concentrations (average 100–500 ants to approximately 4 × 4 cm placement). The recruitment levels for the hydrogel baits were also equal to or greater than those for the commercial paste bait (50–150 ants). However, overall, the shrimp-flavored snack was the food source with the highest levels of recruitment (500–800 ants). The results suggest that in the field, L. humile is moderately to highly interested in hydrogel baits. Hydrogel baits may not be the most efficient bait formulation for recruiting L. humile, but they are a powerful control option due to their advantages such as low cost, which enables thorough treatment. The addition of attractants could help to improve this method in the future.