Effects of a biocontrol agent Chondrostereum purpureum on sprouting of Sorbus aucuparia and Populus tremula after four growing seasons

The efficacy of a decay fungus Chondrostereum purpureum (Pers. ex Fr.) Pouzar to prevent sprouting of two tree species, rowan (Sorbus aucuparia L.) and European aspen (Populus tremula L.) was investigated in a four-growing season study. The efficacy of C. purpureum compared with the control (cutting only) increased during the whole study period indicating that long-term studies are needed to reveal the real effect of the biocontrol treatment. At the end of the study period the mortality of treated rowan stumps was 50 % and that of European aspen 77 %, i.e. clearly higher than in the control with mortality 14 and 52 % respectively. The height of living sprouts was considerably lower in the C. purpureum treatment than in the control. Furthermore, our results indicated that a high number of surrounding conspecific saplings decreased whereas a high number of red raspberry (Rubus idaeus L.) shoots increased mortality of C. purpureum treated stumps.