Effects of defoliation caused by the processionary moth on growth of Crimean pines in western Turkey

Abstract

An outbreak of the pine processionary moth (PPM), Thaumetopoea wilkinsoni Tams (Lepidoptera: Thaumetopoeidae), began in spring 1998 and lasted 6 years in a Crimean pine (Pinus nigra Arnold) plantation in western Turkey. The effects of PPM on the radial, height and volume growth of Crimean pine trees were investigated by examining the increment losses for three defoliation intensities (groups). PPM activity in Crimean pine stand was assessed through radial increment analysis of cores extracted at breast height. In 2004, increment cores were collected from moderate and high defoliation and low defoliation dominant or co-dominant trees. Based on the sample, annual radial growth indices from 1998 to 2004 were calculated. Growth functions were defined as the cumulative sum of radial, height and volume increment graphically compared between Crimean pine defoliation group sample trees. The sample trees are the same subspecies and varieties. After the defoliations, radial, height and volume growth of low defoliation group trees was found to be significantly greater than that of the other affected groups. During the 1998–2004 period the total radial growth of low, moderately affected and highly affected trees was, respectively, 49, 33 and 31 mm; the total height growth was 3.1, 1.8 and 1.0 m; and the total volume growth was 50, 14 and 10 dm3.