Defoliation-Induced Growth Reduction of Pinus sylvestris L. after a Prolonged Outbreak of Diprion pini L.—A Case Study from Eastern Finland

The frequency and intensity of insect outbreaks have increased in boreal forests, along with associated impacts on the growth economic losses host trees. In Finland, common pine sawfly (Diprion pini L.) is a serious pest, causing declines health responses Scots (Pinus sylvestris L.). We focused investigating species’ defoliating impact tree radial volume estimated value declined growth. Managed P. forests our study area eastern Finland suffered from extended defoliation by D. for 15 years since 1999 at varying levels. classified 184 trees into four classes compared annual growth, expressed as indices between classes. modelled volume, loss, those to reference period preceding initial outbreak. found significant differences Growth 4.2%, 20.8%, 40.4% were obtained mild, moderate, high classes, related 51 €, 272 734 € per ha 11 years, respectively. was slightly enhanced lowest class. suggest that growth-related loss caused may be depend outbreak duration.