Influence of Viscum album ssp. austriacum (Wiesb.) Vollm. on tree radial growth of Pinus sylvestris L.

European mistletoe (Viscum album L.) is a semi−parasitic plant attacking selected tree species. It adversely affects the functioning of its hosts especially at water management level. Scots pine infestation by mistletoe subspecies Viscum album ssp. austriacum becomes more and more common. Mistletoe has been proven to have a negative impact on Scots pine cones, seedlings and seeds quality. Thus, we decided to analyze the influence of this parasite on the radial growth of the Scots pine. The following hypotheses were tested: 1) mistletoe has negative effects on the radial growth of trees, and 2) trees infested with mistletoe are more sensitive to climatic factors, especially to low precipitation. The study was performed in western Poland, in the Scots pine excluded seed stand in the Bolewice Forest District (52°23'54'N, 16°05'01'E). We determined the association between pine radial growth and climatic factors (precipitation and temperature). Wood samples(cores) were taken from 15 infested and 15 non−infested trees and subjected to the standard procedure of dendrochronological dating. The study showed that radial growth rate decreased more intensively in trees infested by mistletoes, but it did not show the different climatic response of trees infested and non−infested, probably due to a short time of infestation. Scots pine is the main economic forest species in Poland and mistletoe can significantly affect the growth and development of pines. It is necessary to investigate the impact of mistletoe on stands and ecosystems, as well as to determine the methods of prevention and management of mistletoe tree stands