Effect of defoliation by the pine processionary moth (PPM) on radial, height and volume growth of Crimean pine (Pinus nigra) trees in Turkey

In this study, we assessed the effects of chronic defoliation on radial, height and volume growth of Crimean pine (Pinus nigra Arnold) trees of the pine processionary moth Thaumetopoea wilkinsoni Tams (Lepidoptera:Thaumetopoeidae)] in western Turkey Crimean pine tree ring chronologies were analyzed for evidence of the pine processionary moth (PPM). Tree ring widths from non-defoliated Crimean pine sample trees, which were not defoliated by PPM from 1998 to 2004, were used to estimate potential growth in the defoliated Crimean pine sample trees during the same time interval. In 2004, increment cores collected from 50 defoliated sample trees and 25 non-defoliated sample trees dominant or co-dominant trees. Annual radial growth indices from 1985-2004 calculated for each defoliated Crimean pine and non-defoliated Crimean pine group. We identified regional outbreaks of PPM by synchronous and sustained growth periods of Crimean pine trees. Growth functions of defoliated Crimean pine trees (3) and non-defoliated Crimean pine trees (2) were graphically compared as the cumulative sum of radial, height and volume increment. Two outbreak were identified in 1992 (1992 and 1993) and 1998 (1998-2004) in the study area. PPM caused a significance decrease (average 33%, p<0.05) in the annual radial increment in 1998-2004.