Life cycle of Tomicus destruens in a pine forest of central Italy

Tomicus destruens (Wollaston) (Coleoptera Curculionidae) is a serious threat to the stability of pine forests in the Mediterranean region and along the Atlantic coasts of Portugal, Spain and France. Despite its phytosanitary importance, some aspects of the life cycle of this bark beetle are still unclear. In this study, carried out in a pine forest of central Italy, traps baited with (-)-α-pinene were used to monitor adult flight and the wood colonized by the bark beetle was examined in order to find out more about the life cycle of the beetle and its voltinism. At the study site, the flight of adult beetles for reproduction takes place continuously from autumn to mid-spring of the following year, with a peak of activity in the middle of autumn. Therefore, a part of the adult beetles, of the developing larvae and of the pupae overwinter under the bark of attacked pines, while a part of the adult population overwinter in the pine shoots. Adult beetles of the new generation emerge from the colonized material during the spring and estivate in the pine shoots. The bark beetles never showed flight activity in summer, nor did adults reproduce on pines at that time. Based on the data of the present study, in the environment studied T. destruens completes one generation per year. It remains to be seen whether some of the beetles emerging at the beginning of spring are able to start a second generation in the same year.