PREVENTION OF ENZYME STAIN OF HARDWOODS BY LOG FUMIGATION

Non-microbial sapwood discolorations in hardwood lumber can cause econ omic loss by degrade of quality. Based on the hypothesis that the enzy me-mediated sapstain may develop in part from by-products of parenchym a cells in wood, freshly felled logs of red oak (Quercus spp.) and sug ar hackberry (Celtis laevigata) were fumigated under a plastic tarp wi th methyl bromide. Log sections were checked after fumigation using tr iphenyl tetrazolium dye to confirm death of parenchyma cells. Logs wer e cut into lumber, which was bulk-stacked in warm, humid conditions to promote non-microbial stain in the sapwood. Lumber from those logs un tarped or tarped but not fumigated developed heavy levels of sapstain, whereas lumber from fumigated logs was free of stain. This novel appr oach is being investigated for prevention of other non-fungal stain in wood (e.g., brown stain in softwood) with inclusion of alternate fumi gants.