Spatial distribution of losses in growth of trees caused by the feeding of pine shoot beetles Tomicus piniperda and T. minor (Col., Scolytidae) in Scots pine stands growing within range of the influence of a timber yard in southern Poland

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This study deals with the assessment of increment losses in Scots pine trees caused by the maturation feeding of pine shoot beetles Tomicus piniperda (L.) and T. minor (Hart.) (Col., Scolytidae) in even-aged stands growing during their entire life span within range of the influence of a sawmill and its timber yard. In spring 2004, on three sample plots, 0.2 ha in size, situated 60, 200, and 500 m from the yard, height and dbh of all trees were measured and increment cores were taken from randomly selected sample trees. An agreement between the spatial distribution of losses in tree increments and the distribution of damage to crowns of investigated stands indicated that the losses resulted from the maturation feeding of pine shoot beetles migrating from the sawmill timber yard. Divergence of growth in the about 25-years-old stand indicated the beginning of intensive feeding of beetles in pine shoots with a high level of probability. In comparison with the control stand the basal area losses in stands growing 60 and 200 m from the beetle source amounted to 57% and 46%, respectively. The difference in the height of trees was as large as almost 100%.