Management of Invasive Longhorn Beetles by Targeting the Egg Stage: A Case Study of the Rusty‐Spotted Longhorn Beetle, Apriona swainsoni (Coleoptera: Cerambycidae)

ABSTRACT Managing invasive longhorn beetles (Coleoptera: Cerambycidae) is challenging because their larval development is concealed within host trees. Targeting the egg stage offers a potentially promising approach, as it enables intervention before larvae penetrate the wood. In this study, we investigated the oviposition ecology of the rusty‐spotted longhorn beetle, Apriona swainsoni (Hope)—a recently established invasive longhorn beetle in Japan—and evaluated the effectiveness of egg removal and the contribution of natural enemies to egg mortality. Taking advantage of the unique oviposition behaviour of A. swainsoni , in which females form egg mounds (egg‐laying sites covered with protective material) that can be easily removed, we conducted field experiments in a Maackia amurensis plantation infested by this species. Egg mounds were readily detectable and could be manually removed with simple tools (putative removal rate, 97.7%). The number of points on the bark from which frass had been ejected—an indicator of late‐instar larval density—was 69.4% lower in the treated trees than in the control group the following spring, demonstrating that egg removal can effectively suppress larval infestation and prevent damage to host trees. Predation by several native ant species and the alien assassin bug Agriosphodrus dohrni (Signoret) was directly observed, with 19.0% of egg mounds found to be damaged, indicating that natural enemies contribute to early‐stage mortality. Although this study was conducted at a single site, on a single host species, and during a single oviposition season, the findings provide preliminary evidence that egg‐stage interventions represent an effective component of management for A. swainsoni . The applicability of this approach to other cerambycid beetles will depend on species‐specific oviposition behaviour, egg accessibility, and host plant characteristics. For species with less accessible eggs, chemical or biological treatments might provide alternative means of targeting the egg stage.