Use of the silverleaf fungus Chondrostereum purpureum for biological control of stump-sprouting, riparian weedy tree species in New Zealand

Conventional willow control in wetland and riparian areas of New Zealand is undertaken using cut-stump and/or drill and injection application of glyphosate. The presence of herbicide residues in catchment water supplies has seen the investigation of non-chemical alternatives to poplar and willow control in Auckland water catchment areas. We have demonstrated, in glasshouse trials, the efficacy of an aqueous, gel-based formulation of Chondrostereum purpureum to control the regrowth of crack and grey willow ( Salix fragilis and S. cinerea ). Chondrostereum purpureum isolate ICMP 16392 (isolated from a Prunus sp.) produced the fastest biomass accumulation in liquid culture. Crack willow was significantly more susceptible to cut-stump infection by C. purpureum than grey willow in the glasshouse trial at the end of the 23-week period. Two different formulations were tested; at the end of the trial, there was no significant difference between them with respect to monthly biomass accumulation. Successful field applications of C. purpureum through cut and paste and drill and injection were confirmed by the presence of fruiting bodies on both treated species. Resprouting ability as measured by shoot number was significantly lower on C. purpureum inoculated stumps.