LAUSR

Rubber wood, one of the most preferred plantation timbers in the tropical regions, is easily prone to various moulds, decay and stain fungi. Lasiodiplodia theobromae, the dominant sapstain fungus of rubber wood, causes high economic loss to the industry through its bluish black sap wood discolouration. In our previous laboratory trials, Bacillus subtilis B1 isolated from market available compost was proved as a potent biocontrol agent against the sapstain fungus L. theobromae. The main aim of the present study was to demonstrate the biocontrol potential of B. subtilis B1 against rubber wood sapstain fungus on fresh rubber wood pieces during pre-monsoon, southwest monsoon and northeast monsoon seasons in the field. The visual ratings provided for the wood fungal growth and internal wood stain exhibited the bio-protectant efficiency of B. subtilis B1 even in the southwest monsoon season, which is considered as the most favourable period for the wood fungal growth. Biocontrol agent, B. subtilis B1 demonstrated significant inhibitions of sapstain fungus on open stacked rubber wood pieces in all the seasons. The frequent rainfalls during monsoon periods provide a conducive environment for fungal growth on felled rubber wood. Successful field evaluations of the biocontrol agent during pre-monsoon, monsoon and post-monsoon periods would guarantee year round protection against rubber wood sapstain. B. subtilis B1 displayed holistic biocontrol efficiency towards other stain (Ceratocystis sp., Fusarium sp.), mould (Aspergillus sp., Penicllium sp.) and decay fungi (Trametes versicolor) as well.