The Effects of Pine Processionary Moth (Thaumetopoea wilkinsoni Tams.) on Diameter and Volume Increment in Crimean Pine (Pinus nigra Arnold) Forests of Bartın

The pine processionary moth (PPM) causes damage by eating the needles of trees. It was determined that the normal increment and growth decreased in trees affected by this insect depending on the severity of the epidemic. The aim of this study is to determine the diameter and volume increment losses caused by the PPM in trees in the Crimean pine forests of Bartın province. The research material was obtained from nine temporary trial areas determined in the natural Crimean pine forests of Bartın province. Diameter and height measurements were made on all trees in the trial areas and increment cores were taken from a total of 346 trees. The annual diameter and volume increment values were determined for the period 2010-2021. The period 2015-2017 was determined as loss years. Three classes were created as control, moderate, and high harmful, according to the three-year total diameter increment in the damage years. The differences between the diameter and volume increments of the three classes were checked by the ANOVA and the Duncan test. The effect of climate variables on these differences was examined by the Standardized Precipitation Index and the Erinç Precipitation Efficiency Index. It was understood that increment losses are not affected by the amount of precipitation and temperature. It was determined that there was a 29.89% diameter and 26.72% volume increment loss in the moderate harmful group, and a 40.22% diameter and 35.09% volume increment loss in the high harmful group. Since diameter and volume increment losses have a negative impact on tree wealth and business income, some suggestions were developed to reduce insect damage and ensure sustainable forest management.