Climate-dependent phenological responses of bark beetle in planted pine forests: fluctuations of flight activities and under-bark life stages

The sampling sites were selected based on previously trapped Orthotomicus erosus (Wollaston) adults and personal field observations. Since experimental sites were located in planted pine forests, the same-aged trees were similarly 20-25 cm in diameter among infested locations. Moreover, the sampling sites were irrigated once a month (30 liters of water per tree). On the other hand, no fertilization treatment was used as conservation operations. Two aggregation pheromone traps (ECONEX ORTHOTOMICUS EROSUS 60 DAYS pheromone composed of α-pinene, ethanol, ipsdienol, ipsenol, methylbutenol) were used in each sample site for two years from April 2019 to March 2021. The pheromone traps were placed at a height of 2.5 m from the ground in the south direction of Pinus eldarica trees. The pheromone capsules prepared from the Spanish company Econex were attached to traps and replaced every 60 days based on the company instructions. So that, the numbers of flying adults were recorded using pheromone traps at 10-day intervals from April 2019 to March 2021. To assess the other developmental stages of O. erosus, 15 trees were randomly selected in each examined sites and two 10 × 10 cm bark samples were separated from pine trunks (up to 2 m above the ground). Then, eggs, larvae, pupae and non-flying adults under pine barks were collected and placed in 70% ethyl alcohol for counting. In addition, four climate variables including the mean temperature, relative humidity, wind speed and rainfall were received from Atmospheric Science and Meteorological Research Center.