Impact of defoliation by the pine processionary moth (<Emphasis Type="Italic">Thaumetopoea pityocampa</Emphasis>) on radial,height and volume growth of calabrian pine (<Emphasis Type="Italic">Pinus brutia</Emphasis>) trees in Turkey

An outbreak of the pine processionary moth (PPM),Thaumetopoea pityocampa Schiff. (Lepidoptera: Thaumetopoeidae), began in spring 1998 and lasted 5 years in aPinus brutia Ten. (Calabrian pine) stand. Tree volume and volume elements increments were examined throughout a PPM outbreak cycle from 1981 to 2003, for an even aged, pure, undisturbed, young Calabrian pine stand. Tree ring chronologies of ‘control’ Calabrian pine, which was not defoliated by PPM during the period of 1998–2003, were used to estimate potential growth characteristics in the ‘host’ Calabrian pine (moderate and high defoliation groups) for current and past outbreaks. Increment cores were collected from 70 host and 78 control dominant or co-dominant trees and annual radial growth indices from 1981–2003 were calculated for each defoliation group in a 41 point sampling. Growth functions were defined as the cumulative sum of radial, height, and volume increment, and graphically compared between host Calabrian pine (3 moderate and one high), four control Calabrian pine and one host Crimean pine (Pinus nigra Arnold) sample trees. At least three severe outbreak periods were identified (from 1981–86; 1992–97; and 1998–2003), much of the study area being severely affected by PPM. Tree ring evidence suggests that large scale (in 1981, 1992, 1998) and partial (in 1988) outbreaks occurred in the study area. Negative inflections of host radial growth curves relative to control height and volume indicated PPM activity. The periodic average diameter growth reductions (in %) in 1981, 1988, 1992 and 1998, respectively, were 0, 13, 5 and 0 for control, 12, 8, 7 and 2 for moderate, and 18, 5, 0 and 7 for high defoliation groups. Outbreaks appear to be associated with dry winter and spring weather prior to the autumn and winter in which feeding occurs. http://www.phytoparasitica.org posting Sept. 28, 2004.