Crown Condition as an Indicator of the Incidence of Root Rot Caused by Hetero basidion annosum in Scots Pine Stands

Trees in three Scots pine stands seriously infected by Heterobasidion annosum were classifi ed according to their crown condition into four classes, from healthy to dead trees. After cutting the stands, the classifi cation was compared with the symptoms of annosum root rot on stump surfaces (pitched area) and with the extension of decay in the roots of excavated stumps. When dead trees were included, the average crown condition on the survey plots correlated with disease incidence. Without dead trees the correlation was not signifi cant. Slightly infected trees could not be distinguished from healthy trees on the basis of crown condition. It was concluded that only the proportion of dead and dying trees in a stand is a reliable indication of the disease incidence for making decisions about the future management.