Effects of dinotefuran trunk injection against the red-necked longhorn beetle Aromia bungii (Coleoptera: Cerambycidae) in Japanese flowering cherry trees

The control effects of a commercial-grade dinotefuran formulation "Wood-Star" applied via trunk injection against Aromia bungii larvae infestation in Japanese flowering cherry trees were evaluated. Twenty test trees were injected with this formulation in late April 2019, and the number of larval frass-excretion-holes with newly ejected frass (hereafter "active frass-holes") in both treated and untreated trees was investigated weekly from April to May in 2019 and 2020. In addition, adult emergence-holes that occurred in 2018, 2019, and 2020 on each tree were counted. The total number of active frass-holes decreased by 21.2% in treated trees and increased by 178.9% in untreated trees within 4 weeks after injection. The insecticidal efficacy of the formulation was estimated as 88.2% based on the decreasing number of active frass-holes in the treated trees. Generalized linear models for the number of active frass-holes and newly occurring emergence holes suggested that dinotefuran treatment decreased the larval activity for at least 4 weeks, resulting in the suppression of emerging adults in the next year of treatment. However, active frass-holes and newly occurring emergence holes were observed in some treated trees in the succeeding year of the treatment. This suggested the possibility that the injection treatment in late April was, at least partially, invalid to control A. bungii larvae that originated from the eggs deposited in the adult reproductive period (June to August) of the treatment year.