Abstract
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.
Highlights
The harm caused by invasive alien species to native ecosystems and biodiversity is becoming more serious (Bellard et al 2016; Blackburn et al 2019; Clavero and GarcíaBerthou, 2005)
Asia has been invaded by ants of diverse origin and taxonomy, beginning with the tropical fire ant, Solenopsis geminata (Fabricius) (Hymenoptera: Formicidae) (Gotzek et al 2015), followed by the Argentine ant Linepithema humile (Mayr)
Past successful cases of the eradication of invasive alien ants show that insecticides use, i.e., chemical control, is the most promising method (Hoffmann et al 2016)
Summary
The harm caused by invasive alien species to native ecosystems and biodiversity is becoming more serious (Bellard et al 2016; Blackburn et al 2019; Clavero and GarcíaBerthou, 2005). The most serious invasive alien ant species is the red imported fire ant S. invicta Buren (Hymenoptera: Formicidae) (Tschinkel 2006; Wetterer 2013; Wylie et al 2020) This species originated in South America and invaded the USA in the 1930s (Wetterer 2013). In September 2020, a mature nest with 50 newly-emerged queens was found at Nagoya Port (Ministry of the Environment 2020b) In this imminent situation, there is an urgent need to establish a method for the control of S. invicta. Past successful cases of the eradication of invasive alien ants show that insecticides use, i.e., chemical control, is the most promising method (Hoffmann et al 2016). In post-establishment control, toxic baits with slow-acting chemicals are effective (Hoffman et al 2016). The basic toxicity data obtained will be very useful for optimizing pre- and postestablishment control of S. invicta
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