Transovarial effects of pyriproxyfen on Japanese beetle (Coleoptera: Scarabaeidae) in turfgrass

The Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), is a serious pest of landscape trees, shrubs, and turfgrass in the eastern United States. Currently, adults and larvae of P. japonica are targeted using repeated insecticide applications. Pyriproxyfen, an insect growth regulator (IGR), whether applied topically to adult P. japonica or ingested by them, reduces egg viability. However, the transovarial effect of IGRs on adult P. japonica is inadequately studied. Thus, the objective of this study was to determine whether transovarial activity of pyriproxyfen affects F1 grubs (offspring) density. In 2023 and 2024, field studies were conducted after exposing adult P. japonica to the maximum label rate of pyriproxyfen. The treatments were (i) dipping in solution, (ii) feeding on treated foliage, (iii) combined dipping + feeding, and (iv) a nontreated control. Results showed that the number of grubs was significantly lower in the dipping + feeding treatment than in the nontreated control treatment in both years. These findings demonstrate the potential of pyriproxyfen as a transovarial management tool for P. japonica and provide insight for integrated pest management in turfgrass and ornamental landscapes.