Field tests on biological control of Heterobasidion annosum by Phaeotheca dimorphospora in comparison with Phlebiopsis gigantea

In field tests conducted on freshly cut red pine (Pinus resinosa) logs, the antagonistic fungus Phaeotheca dimorphospora formulated as pre-colonized rye grains reduced colonization of wood tissue by Heterobasidion annosum to less than 2% over the 2 months following inoculation. However, compared to controls, a water suspension of P. dimorphospora did not reduce the infection, but rather promoted colonization by H. annosum after a 2-month exposure. Production of antifungal metabolites by P. dimorphospora in the rye grains and better colonization of the logs by the antagonist were observed with the rye grain formulation. In this field test, the most effective treatment to control H. annosum was the application of an oidial suspension of Phlebiopsis gigantea . This fungus completely inhibited colonization by H. annosum mostly by rapid colonization of wood tissue. All treatments with P. gigantea, P. dimorphospora and rye grains influenced the naturally occurring mycoflora. The most important species composing this mycoflora were Hormonema sp., Mortierella spp., Mucor hiemalis f. hiemalis, Nectria sp., Pesotum sp., P. gigantea, Tympanis spp., Trichoderma spp. and an unknown basidiomycete.