Effect of delayed toxicity of chemical barriers to control Argentine ants (Hymenoptera: Formicidae)

Brief exposures of Argentine ants to four different insecticide treatments, bifenthrin, beta-cyfluthrin, bifenthrin + beta-cyfluthrin, and fipronil, were conducted to determine Kaplan-Meier product limit survivorship percentiles (SPs) at 21-23 and 27-29 degrees C. Bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin provided rapid kill at 21-23 degrees C with SP10 values ranging from 11.2 to 33.7 min. Fipronil provided delayed toxicity at 21-23 degrees C with SP10 values ranging from 270 to 960 min. At 27-29 degrees C, all of the SP10 values significantly decreased. Field tests in which Argentine ants were induced to forage across insecticide-treated surfaces were used to determine the effect that speed of action has on foraging and recruitment ability, and whether these insecticides are repellent. The slower-acting fipronil allowed a greater amount of foraging and consequently a greater fraction of the colony to be exposed, whereas fast-acting bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin inhibited recruitment, resulting in fewer ants being exposed and killed. Implications for controlling ants by using perimeter barrier treatments are discussed.