Biological control of blue stain fungi on Populus tremuloides using selected Ophiostoma isolates

Single ascospore isolates of Ophiostoma piceae and O. pluriannulatum were selected for lack of hyphal pigmentation and their inability to stain aspen wood. Several colorless strains were tested in laboratory and field studies for their potential to control sapstain in aspen wood. A previously selected and commercially available fungus used in biopulping processes, Cartapip-97, was also tested for controlling stain fungi. The colorless Ophiostoma isolates successfully prevented staining of sterile wood in the laboratory when challenged by a wild type staining isolate of O. pluriannulatum. The colorless strains also aggressively colonized nonsterile aspen wood in laboratory and field trials and significantly reduced sapstain. In the field trials, colorless isolates significantly reduced colonization of wild type Ophiostoma species by as much as 75 % and reduced colonization in logs challenged with an aggressive wild type sapstain fungus by 37 to 58 %. Aspen logs treated with colorless strains were visually free of sapstain. Wood extractives were also significantly reduced by 28 to 33 % after treatment with colorless strains as compared to fresh, untreated wood.