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Biodegradable alginate hydrogel bait delivery system effectively controls high-density populations of Argentine ant in commercial citrus

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The Argentine ant, Linepithema humile (Mayr), poses a significant economic threat to citrus production in southern California. Broad-spectrum insecticide sprays provide poor ant control and present a hazard to human and environmental health. Liquid sucrose bait infused with a low concentration of insecticide is an effective alternative treatment but current approaches require considerable economic investment in plastic dispensers and continual maintenance. To produce a baiting product for control of L. humile suitable for large-scale application, a biodegradable, broadcastable alginate hydrogel for delivery of aqueous low-dose thiamethoxam sucrose bait was developed and evaluated in replicated field trials in commercial citrus groves. Ant activity was significantly reduced in hydrogel-treated trees. Peak L. humile suppression was achieved 48 h following the final hydrogel disbursement, with an estimated 91% reduction in activity from baseline estimates and a 17-fold lower activity in treated trees in comparison with untreated trees. Significant residual activity of the hydrogel treatments was recorded, with a nearly 70% reduction from pre-treatment levels persisting at least 3 weeks after the last application. We conclude that alginate hydrogels can provide excellent control of L. humile while deploying 99.99% less insecticide into orchards than commercial barrier spray treatments.

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This work was supported, in part, from funds provided by the California Department of Pesticide Regulation Agreement Number 15-PML-R002 and the Citrus Research Board Agreement Number 5500-194. The authors greatly appreciate the contributions of several field and laboratory technicians: Kathleen Campbell, Kelly Giordano, Michael Patini, Michael Lewis, and Carly Pierce. They also thank Suterra LLC. for providing the putative Argentine ant trail pheromone formulation used in the hydrogel bait formulation. They acknowledge the support of cooperating citrus growers who graciously provided unlimited access to their orchards for conducting field trials.

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Correspondence to Kelsey A. McCalla.

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McCalla, K.A., Tay, J., Mulchandani, A. et al. Biodegradable alginate hydrogel bait delivery system effectively controls high-density populations of Argentine ant in commercial citrus. J Pest Sci (2020). https://doi.org/10.1007/s10340-019-01175-9

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  • Argentine ant
  • Commercial citrus
  • Ant control
  • Bait
  • Biodegradable hydrogel
  • Thiamethoxam