A seven-year monitoring of Orthotomicus erosus (Wollaston) in Tuscany, Italy: observations on life cycle, damage, and trapping

The Mediterranean Pine Beetle Orthotomicus erosus (MPB) (Coleoptera: Curculionidae: Scolytinae) is considered a minor pest in Italy, primarily infesting recently dead or severely stressed pines. However, during periods of high population density, it can also colonize healthy trees. Thus, its role may shift due to global warming and the ongoing decline of pine forests. Beyond its native range, MPB is a significant biosecurity concern, as evidenced by frequent interceptions at ports of entry and a high risk of establishment. This study presents seven years of research in Tuscany, Italy, examining pheromone trap catches, life cycle dynamics, and the efficacy of the repellent verbenone. In 2016-2019 and 2022-2024 nearly one million MPB adults were trapped. Flight activity was recorded from March to December, with two-three overlapping generations. Trap model and position significantly influenced catch rates. Lindgren traps in the canopy captured up to twice as many specimens as Theysohn traps on the ground. Traps under more dense forest cover were more effective than those exposed to sun and wind due to sanitary logging. On symptomatic trees, MPB signs sometimes co-occurred with those of Tomicus destruens and Ips sexdentatus. However, some trees were attacked exclusively by MPB, particularly in the absence of the other two major species or when their reproductive flights were unsynchronized. This confirms MPB’s ability to kill weakened pines independently, colonizing trunks up to 40 cm in diameter. In addition, this study confirmed that verbenone reduced the attractiveness of aggregation pheromones, thus corroborating the possibility of its use as repellent against MPB. In fact, catches were reduced by up to tenfold if the repellent was added to pheromone traps. To conclude, these findings provide valuable insights into the ecology of MPB and contribute to the development of more effective monitoring and management strategies for this emerging bark beetle species.