Abstract

Sapstain caused by fungi results in considerable qualitative loss of wood products. Due to favourable environmental conditions such as high rainfall and humidity, sapstain is a serious problem in Kerala. A preliminary survey conducted in various woodbased industries in different districts of Kerala State revealed that sapsatin and mould growth were caused by a number of fungi. Eight commercially important timber species were selected for the study and Botryodiplodia theobromae was found to be the dominant fungus causing sapstain on all the timbers through out the year. Studies revealed that in rubber wood infected by B. theobromae there was a weight loss of 8.0 in the first month which increased to 12.2 by the end of fourth month. In Ailanthus triphysa the weight loss increased from 4.3 in the first month to 10.1 in the fourth month. But in Alstonia scholaris only 4 weight loss was recorded by the end of fourth month. The results clearly showed that rubber wood was easily susceptible to sapstain by B. theobromae. Effect of wood moisture content and microclimatic factors on growth of B. theobromae was studied and it was found that the growth of the fungus was influenced by high relative humidity (90 and 100). When the moisture content of timber was reduced to 24, the fungal growth on timber was very much restricted. Among the various fungicides/chemicals tested, sodium azide proved to be the best to control both sapstain and mould fungi in the laboratory. The chemical was effective even at lower concentrations viz. 250 and 500 ppm. A bacterium viz. Bacillus subtilis, isolated from rubber wood, showed antagonism against several stain and mould fungi. The efficacy of this isolate was tested in laboratory and proved to be effective in controlling the growth of several stain fungi. In field tests also, the bacterium was effective in preventing the fungal growth on rubber wood up to 80