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Invasive Species

A Program to Eradicate Argentine Ants for San Clemente Island, California


Aaron Hebshi, Senior Natural Resources Specialist, Naval Facilities Engineering Systems Command – Southwest:


The Argentine ant (Linepithema humile), a tramp ant now common in many subtropical and temperate locations, has been considered to be one of the most ecologically destructive invaders worldwide. Argentine ants are widespread in coastal California, and were found on San Clemente Island (SCI) in 9 discrete sites associated with facilities in 2013. Argentine ants threaten SCI’s native ant community (14 species) and multiple ESA-listed and sensitive species through ecological cascading effects. In 2014, the US Navy initiated a treatment program with the goal of full Argentine ant eradication from the island. The eradication protocol entails applying a toxicant bait containing sugar, water, and the neonicotinoid Thiamexthoxam (under the trade name Optigard Flex), absorbed into polyacrylamide beads and applied using hand-held fertilizer spreaders and via helicopter. Overall, 1700 acres have been treated at a cost of $2.87M. The infestation currently covers approximately 1595 acres. Treatments are ongoing, and we hope to meet our goal of finishing all major treatment operations by 2026.

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