Abstract

Microorganisms cause various types of damages such as decay, soft rot, mould, stain and bacterial degradation to timber. Moulds and stain are common on rubber wood. The predominant fungal species causing sapstain in rubber wood is Botryodiplodia theobromae. Due to the environmental conditions favourable for fungal growth, sapstain is a serious problem preventing the utilization of rubber wood in Kerala. This report presents a detailed study on the factors affecting the growth and colonization of B.theobromae occured in rubber wood. The study has revealed that no growth of B.theobromae occurred in rubber wood with a moisture content at or below 23.8 per cent. Moisture content of 29.0 per cent or above was not favourable for heavy growth of the fungus. Temperature tolerance of B.theobromae showed that 30 degree celcius was the ideal temperature for the growth of the fungus on Potato Dextrose Agar medium. The results also indicated that once. B.theobromae was established in the wood, the mycelium wasnot killed on the surface as well as inside the wood even after 7 days of incubation at 50 degree celcius. Weight loss of rubber wood due to B.theobromae infection was 8 per cent in the first month which increased to 12.2 per cent at the end of the fourth month. But in Alstonia scholaris , the weight loss was 4.5 per cent at the ends of fourth month. There was also a reduction in the compressive strength of stained wood was noted, whereas the bending strength was reduced. In the field evaluationn of different chemicals/fungicides for the control of sapstain and decay, captafol even at 3 per cent did not prevent mould and sapstain fungi completely on rubbber wood. In all the fungicidal treatments, better control was achieved by open stacking. Busan 1009(1.0 per cent) mixed with boric acid (1.0 per cnet) and borax (1.0 per cnet) was effective in controlling fungal growth. also, Hylite extra at 1.5 per cnet, and Chlorothalonil at 1 per cent were equally effective in controlling sapstain. During rainy season, appropriate concentration of the fungicides has to be increased for better control of fungal growth