Determination of sawdust concentration for inhibitory effect against Rhizoctonia solani, a causal agent of damping off of cotton fibre

Cotton is one of the most important fibre plants with much more products being manufactured from it than most other fibre . Apart from fibre, it is used for explosives, cottonwool, etc, and the seed is used principally for the manufacture of oil, soap, animal feed and fertilizers, producing practically no waste. To determine the effective sawdust concentration to inhibit the growth of Rhizoctonia solani which causes damping off of cotton fibre , this work was carried out in the Laboratory of the Department of Microbiology and Biotechnology, Gono Bishwabidyaloy, Savar, Dhaka, Bangladesh during the period of October, 2010 to December, 2011. The experiment indicates that sawdust amendmends at 4000 ppm gave the maximum mycelial growth (90mm) which was similar with the control treatment result whereas no radial mycelia growth was found when sawdust amendmends at the concentration of 16000, 18000 and 20000 ppm were applied. The growth of R. solani was completely inhibited when the sawdust amendmends at the concentration of 16000 ppm and onward were given. So to suppress the complete growth of a causal agent of damping off of cotton fibre like R. solani ; organic amendmends like sawdust at proper concentrations are suggested to use.