| The Argentine ant, Linepithema humile (Mayr), is an extremely invasive ant species that has spread to urban, commercial and natural areas worldwide. This expansion has had detrimental ecological and economic effects, resulting in the allocation of vast amounts of resources to its control in urban and agricultural areas. Efforts are underway to control Argentine ants in ecologically sensitive habitats, such as San Clemente Island, CA. We tested the treatment efficacy of liquid bait in ecologically sensitive habitats using polyacrylamide beads as a delivery matrix. In 2014, five sites (176.95 ha) were treated with this toxicant bait seven times in five months resulting in an initial 99.86% reduction in Argentine ant activity across the five sites. In summer 2015, we conducted low-density intensive monitoring over a 17-hectare area using bait traps in a 3m by 3m grid design. We found recolonization of native ants at and remnant colonies of Argentine ants one year after pesticide application. The polyacrylamide bead delivery matrix was successful in reducing Argentine ant numbers, as shown by this study. Persistent treatment and monitoring will be necessary to ensure complete eradication of Argentine ants from San Clemente Island. |