Efficacy of Dinotefuran Trunk-Injection Treatment against Larvae of the Invasive Rusty-Spotted Longhorn Beetle, <i>Apriona swainsoni</i>（Coleoptera: Cerambycidae）, Infesting the Legume Tree, <i>Maackia amurensis</i>

The rusty-spotted longhorn beetle, Apriona swainsoni（Hope）（Coleoptera: Cerambycidae）, is an invasive longhorn beetle species first detected in Japan in 2021. It infests the legume tree, Maackia amurensis, and other host trees, causing a severe decline in tree vigor and even tree collapse. Due to its ecological impact, the species has been designated as a “Designated Invasive Alien Species” under the Invasive Alien Species Act, and urgent control measures are required. However, no effective chemical control method has been established to date. In this study, we evaluated the larvicidal efficacy of trunk-injection using a dinotefuran 8% solution at a plantation site in Koriyama City, Fukushima Prefecture. Twenty infested M. amurensis trees were selected, with ten assigned to a treatment group and ten to a control group. The number of frass-extrusion sites was recorded before treatment and again eight months later. In the control group, an average of 53.9% of frass-extrusion holes ceased activity by the following spring. In contrast, the treatment group showed an average cessation rate of 86.5%, indicating a significant insecticidal effect of dinotefuran. Further investigation is needed to assess its efficacy against adult beetles and the duration of residual activity, toward establishing an integrated management strategy.