Laboratory and Field Evaluations of Two Bait Formulations Against the Invasive Fire Ant, Solenopsis invicta (Hymenoptera: Formicidae).

The red imported fire ant, Solenopsis invicta Buren, was first discovered in Japan in 2017. As this ant remains at the early invasion stage, efforts in establishing a rapid-response framework, such as evaluating available control methods, are urgently needed. Despite the presence of numerous household insecticides against invasive/household pest ants in Japan, the effects of these products on fire ants remain poorly understood. This study assessed the efficacy of two bait products designed to target common household ant pests in Japan on S. invicta through under laboratory and field conditions in Taiwan. The two baits are Arino-su-korori (AK), a granule-formulated bait product with hydramethylnon as an active ingredient (A.I.), and Hyper Arino-su-korori (HAK), a paste-formulated bait with fipronil as A.I., respectively. We showed that both AK and HAK resulted in more than 99% mortalities of fire ant within 8 wk under laboratory conditions and significantly reduce fire ants' foraging activities in the field. AK generally performed slightly better than HAK in terms of the time required to achieve total laboratory colony elimination and also long-term suppression of field fire ants. Such differences most likely are attributable to the active ingredient's mode of action and/or formulation and their interactions with fire ant biology. This study demonstrates the feasibility of the two bait products in effectively controlling laboratory and field fire ants, thus representing a promising candidate pest management tool to cope with ongoing/future fire ant invasions in Japan.