Effect of application time on the efficacy of Chondrostereum purpureum treatment against the sprouting of birch in Finland

Abstract

To test the effect of application time on the efficacy of a biological control agent to prevent sprouting of cut stumps, birches ( Betula pendula Roth. and Betula pubescens Ehrh.) were cut and stumps treated with a decay fungus ( Chondrostereum purpureum (Pers. ex Fr.) Pouzar) at different times during one growing season. Applications were conducted at 2 week intervals. The presence of fruiting bodies was examined three times during the 2 years following treatment. Sprouting was measured twice. Fructification was most abundant 1 year after the treatment, and the frequency of stumps with fruiting bodies was highest when the stumps were treated between May and July. Treatment reduced the percentage of living stumps compared with controls, except if conducted in late autumn. The reduction was the highest on stumps treated in the middle of July; 2 years after the treatment, only 12.5% of treated stumps were resprouting compared with 74% of control stumps. Also, the number of living sprouts per stump decreased by the treatment, except if conducted in late autumn. Although the number of living sprouts per stump decreased owing to C. purpureum treatment, it had no effect on the maximum height of the sprouts.