Acute toxicity of typical ant control agents to the red imported fire ant, Solenopsis invicta (Hymenoptera: Formicidae)

The red imported fire ant Solenopsis invicta Buren (Hymenoptera: Formicidae), is a serious invasive alien ant around the world and has expanded its invasive range to the Pacific Rim since the early 2000s. It was first reported in Japan in 2017, and its entry through cargo has been reported numerous times in many ports. Colonies have been found in Tokyo Port since 2019, and now it is an urgent issue to prevent further invasion and establishment. Chemical control is the best tested method of insect control, but we have little information on the efficacy of insecticides against S. invicta in Japan. Here, we conducted acute toxicity assays of six quick-acting pyrethroids (transfluthrin, prallethrin, phenothrin, permethrin, metofluthrin, and pyrethrin) for killing adults and five new-type insecticides (fipronil, thiamethoxam, indoxacarb, imidacloprid, and hydramethylnon) for controlling colonies with toxic baits. We found that the LD50 from six pyrethroids were comparable to each other. The ED50 causing abnormal behaviors were smaller than LD50, but some ants recovered from paralysis within 12 h. Fipronil showed the lowest LD50 suggesting this chemical is the most promising agent for controlling S. invicta. Our results promise to develop a method for the chemical control of S. invicta.

Automated summary

The red imported fire ant is a serious invasive alien ant that has expanded its invasive range to the Pacific Rim since the early 2000s. However, little information is available on the efficacy of insecticides against S. invicta in Japan. Research has shown that fipronil is the most promising agent for controlling S. invicta.