Effects of two fumigants and a fungicide formulation on the development ofkiln brown stain in radiata pine lumber

Two fumigants (methyl bromide and sulphuryl fluoride) were used to treat fr eshly sawn radiata pine (Pinus radiata D. Don) lumber and log sections to e valuate their influence on development of kiln brown stain. Both treatments reduced severity of stain when compared with controls. The sulphuryl fluor ide treatment was notably better than methyl bromide at the highest fumigan t dosage, but levels of overall stain were still considered unacceptable wi th only 20-30% of lumber having either no or slight stain beneath the surfa ce. Sulphuryl fluoride showed superior penetration into sapwood compared to methyl bromide as determined by a colour assay of parenchyma cell viabilit y. A fungicide formulation which was successful in preventing brown stain i n kiln dried eastern white pine was ineffective against kiln brown stain in radiata pine. The results of the present study indicates that the mechanis m for kiln brown stain in radiata pine differs from that in eastern white p ine.