Biological control of blue stain in pulpwood: Mechanisms of control used by Phlebiopsis gigantea

Phlebiopsis gigantea, a white-rot fungus currently being tested in biologic al processing applications for the pulp and paper industry, was shown to ef fectively inhibit blue stain fungi in both laboratory and field trials. Ino culation of logs with P. gigantea shortly after cutting resulted in up to 8 6 % colonization of logs in the laboratory and 100 % in field studies. Colo nization of logs by blue stain fungi such as Ophiostoma piliferum and O. pi ceae was greatly reduced or completely inhibited with prior inoculation by P. gigantea. In field studies, blue stain fungi colonized up to 53 % of the sapwood and stained as much as 31 % of the sapwood in non-inoculated contr ol logs in contrast to 4 % colonization and 2 % stain in treated logs. Logs inoculated with O. piliferum 2 weeks prior to inoculation with P. gigantea were 88 Sc colonized by O. piliferum and had 33 % of the sapwood stained a fter 7 weeks, and 33 Q colonized and 18 Pc stained after 29 weeks. Scanning electron micrographs of P. gigantea and O. piliferum hyphae showed P. giga ntea parasitizing the blue stain fungus. Phlebiopsis gigantea was shown pen etrating and growing adjacent to collapsed and disintegrated blue stain hyp hae. Phlebiopsis gigantea also decolorized sapwood previously stained blue.