Log fumigation prevents enzyme-mediated sapwood discolorations in hardwoods
E L Schmidt, T L Amburgey
Non-microbial sapwood discolorations in hardwood lumber can cause economic loss by degrade of quality. Based on the hypothesis that the enzyme-mediated sapstain may develop in part from byproducts of parenchyma cells in wood, reshly felled logs of red oak (Quercus spp.) and sugar hackberry (Celtis laevigata) were fumigated under a plastic tarp with methyl bromide. Log sections were checked after fumigation using triphenyl tetrazolium dye to confirm death of parenchyma cells. Logs were cut into lumber which was bulk-stacked in warm, humid conditions to promote non-microbial stain in the sapwood. Lumber from those logs untarped or tarped but not fumigated developed heavy levels of sapstain whereas lumber from fumigated logs was free of stain. This novel approach is being investigated for prevention of other non-fungal stain in wood (eg. brown stain in softwood) with inclusion of alternate fumigants.