Biology of Euwallacea interjectus (Coleoptera: Curculionidae: Scolytinae), an emerging poplar pest in East China.

Euwallacea interjectus (Coleoptera: Curculionidae: Scolytinae), an ambrosia beetle native to East Asia, has become a significant pest of poplar plantations in China, yet its field biology under natural conditions remains poorly documented. We investigated the seasonal biology, flight activity, gallery population dynamics, and host attack characteristics of E. interjectus in poplar plantations in Yancheng, Jiangsu Province, China, from June 2021 to October 2022 by using ethanol-baited trapping, gallery dissection, artificial colonization, and field surveys. Adult flight of E. interjectus occurred from early April to late October and exhibited multiple seasonal peaks, with the peak flight activity recorded from June to August. Gallery dissections showed that the pest completed four generations annually, with overlapping generations during the active season, and overwintered primarily as adults within galleries. The mean developmental duration from egg to adult was approximately 36 days under field conditions. Seasonal changes in gallery populations were generally consistent with trap captures throughout the flight season. Beetle attacks were concentrated on the lower trunk, with 83.30% of entrance holes occurring below 3.0 m, and attack density increased significantly with tree diameter at breast height, indicating preferential colonization of larger trees. These findings provide a comprehensive characterization of the annual field biology of E. interjectus and provide biological information for improving monitoring programs and management strategies in poplar plantations.