Quantifying the spread of a novel soft bait through colonies of the red imported fire ant

Red imported fire ants, Solenopsis invicta, have been a major pest in the southeastern United States since they were introduced into Alabama in the 1930’s. Insecticidal baits are one of the primary control tactics used to suppress populations of fire ants. In this study, we quantified fire ant worker recruitment to and subsequent spread of a novel soft bait within fire ant colonies to test the potential efficacy of this bait. Rhodamine B dye was added to each soft bait so that the dispersal of food to the larvae could be monitored with a black light. Three different artificial nectars containing sugars, amino acids, or sugars in combination with amino acids were mixed with 0.5% Rhodamine B by mass and included in the soft bait. Foraging fire ant workers strongly preferred soft baits containing sugars, and these baits were rapidly returned to fire ant colonies where the workers transferred dyed bait to larvae via trophallaxis. Significantly more larvae received the soft baits containing sugars than soft baits containing water (control baits) or amino acids alone. This study suggests that our novel soft baits containing sugars will be able to deliver insecticides to a large percentage of the larvae within a fire ant colony.