Chondrostereum purpureum-based Control of Stump Sprouting of Seven Hardwood Species in Lithuania

The ability of Chondrostereum purpureum preparates to control sprouting of seven hardwood species in Lithuania one year following applications was tested: native Betula pendula, Alnus incana, Populus tremula and Salix caprea, and invasive Acer negundo, Hippophae rhamnoides and Robinia pseudoacacia were inoculated with C. purpureum. The experiments were performed twice: in July and October 2010. Each time, twenty trees of each species were cut and inoculated with four Lithuanian strains of C. purpureum using two formulations: i) mycelial water suspension mixed with 'AgroAquaGel'(R), and ii) mycelial water suspension mixed with xanthan gum and glycerine. Two different types of negative controls were used: a blank formulation control and a slash control. Herbicide 'Roundup (R) BIO' was used as a positive control. All four inoculated strains of C. purpureum persisted in treated stumps of B. pendula, A. incana, P. tremula, S. caprea and A. negundo, formed abundant fruitbodies, and showed similar effect in preventing sprout formation. Compared to negative controls, mycoherbicide treatment in summer had significantly reduced percentage of living stumps and sprouts on B. pendula and A. negundo (the effect was as good as of chemical herbicide) as well as mean height of the tallest living sprout of these species. A slight effect of C. purpureum treatments on stump and sprout mortality was observed for A. incana, P tremula and S. caprea, although fruitbody formation occurred after treatment. No mycoherbicide effect was observed on R. pseudoacacia and H. rhamnoides which arc either resistant to C. purpureum infection or symptom development is delayed relative to the other species tested. Summer treatments gave significantly better results than the autumn treatments in terms of stump and sprout mortality: 75.9% and 38.5% of the stumps, and 83.6% and 46.0% of the sprouts were dead in summer and autumn treatments, respectively (pooled data from B. pendula, A. incana, P. tremula, S. caprea and A. negundo plots). There was no seasonal treatment effect on fruitbody formation. In conclusion, local strains of C. purpureum can be successfully applied to control stump sprouting of B. pendula and A. negundo in Lithuania if performed during a period of active tree growth.