Use of an Argentine Ant, Linepithema humile, Semiochemical to Deliver an Acute Toxicant

The Argentine ant, Linepithema humile, is an invasive nuisance, agricultural, and ecological pest from South America. In the United States, its primary distribution is in California and the Southeast. The structural pest control industry responds to property owner complaints when this ant's populations become problematic and a persistent nuisance. Actions taken to control Argentine ants in the urban and suburban environment are typically complaint-driven, and often involve the application of insecticide sprays applied to the outdoor environment by professional pest managers. In California, and elsewhere, spray treatments of various residual insecticides by property owners and pest management professionals has resulted in significant runoff and in subsequent surface water contamination. As a result, an immediate need exists to develop alternative methods of ant control targeted at reducing environmental contamination. The purpose of this study was to investigate the potential for the development of an alternative method of toxicant delivery focused on the Argentine ant's behavior modifying cuticular chemistry. In short, methanol and hexane washes of Argentine ant pupae applied to paper dummies were handled significantly more by worker ants than the paper dummies that did not contain the solvent extracts. Additionally, paper wicks soaked in a methylene chloride wash from Argentine ant cadavers, air dried, and then treated with fipronil, were removed by worker ants and placed on a midden pile at the same rate (≈86% to 99% removal at 1 h) as untreated and fipronil-treated ant cadavers. The paper wicks that did not contain the methylene chloride extract were ignored by the worker ants. After three days, the mortality of the ants exposed to the fipronil-treated wicks or the ant cadavers were dose-related. In conclusion, our study suggests that there is potential for the use of ant semiochemicals for the delivery of acute toxicants.