Argentine Ant Management: Using Toxin-Laced Polyacrylamide Crystals to Target Ant Colonies in Vineyards

Abstract

Summary Goals: Argentine ant (Linepithema humile) is an invasive species that is ecologically disruptive and agriculturally significant. In vineyards, Argentine ant activity compromises nonchemical approaches to mealybug management by interrupting biological control agents. Toxic baits have proven effective to control Argentine ant populations in urban and agricultural settings; however, it is resource intensive to use bait stations to deliver a toxin to ants, making it prohibitive to large-scale implementation by agricultural producers. We undertook this project to evaluate a simpler, more efficient delivery method, using toxin-laced polyacrylamide crystals. Key Findings: Polyacrylamide baits are quick and easy to prepare and apply in vineyards. Both boric acid (0.5%) and thiamethoxam (0.0006%) are compatible with the polyacrylamide crystal delivery method. In vineyards, two applications of thiamethoxam-laced bait eliminated ant foraging at sugar-soaked cotton balls for 5 to 6 wks and further suppressed activity for up to 6 mos. In vineyards, two applications of boric acid-laced bait eliminated ant foraging at sugar-soaked cotton balls for 4 to 6 wks and further suppressed activity for up to 5 mos. Overall temporal declines in ant populations in the trial blocks suggest that there are cumulative effects of the bait applications over multiple seasons. Impact and Significance: Toxic bait applied in commercial vineyards using a novel delivery method, polyacrylamide crystals, provided durable control of Argentine ant populations during the growing season. Following two bait applications, ant foraging at sugar-soaked cotton balls was eliminated for 5 to 6 wks and further suppressed for 3 to 6 mos; in several instances, this effect continued into the subsequent growing season. The broadcast toxin-laced crystals were spread across a large area of the vineyard, facilitating ant foraging at multiple point sources to target a greater number of nests within the infested areas. The sugary, aqueous bait mimicked their natural food source, making it attractive to foraging ants and therefore more likely to result in sustained population control. Using these baits to reduce Argentine ant populations in vineyard ecosystems can reduce their agricultural significance by enhancing biological control of phloem-feeding insects, particularly mealybugs. Other ecological benefits may also result from reducing populations of this invasive species in agricultural and natural systems.1,2,3