FUNGAL STAINING OF PONDEROSA PINE SAPWOOD - EFFECTS OF WOOD PRECONDITIONING AND BIOPROTECTANTS

Differences in stain susceptibility were evaluated on sterile and unsterile samples of freshly sawn, frozen and thawed, or oven-dried and rewetted ponderosa pine sapwood. Samples treated with sterile medium or with medium inoculated with either Pseudomonas putida or Bacillus subtilis were inoculated with selected wood-staining fungi. In general, fresh unsterile samples were less stained than either frozen or oven-dried wood. Sterilization by either steaming or gamma irradiation generally eliminated the differences in degree of stain noted in unsterilized specimens exposed to the various initial wood conditions. Sterilization alters either the microflora or the nutritional quality of the wood, enhancing fungal wood-staining. Therefore, unsterile, freshly sawn wood should be used in assessing the efficacy of bioprotectants.