Evaluation of fungitoxicants and Trichoderma against Macrophomina phaseolina causing root rot of cotton

Root rot disease caused by Macrophomina phaseolina is one of the major soil-borne diseases of cotton and is responsible for poor crop stand and lower yield. It causes total yield loss in patches in the infected field. Therefore, eight fungicides viz. carbendazim, thiram, carboxin + thiram, thiophanate methyl, MEMC (Emisan-6), captan, captan + hexaconazole and carbendazim + mancozeb were evaluated against M. phaseolina for their toxicity to Macrophomina phaseolina under in-vitro condition at four concentrations. In-vitro growth inhibition test revealed that the fungicides varied considerably in their toxicity to Marophomina phaseolina. Carbendazim and MEMC at 10 ppm concentration were found most effective fungicides with highest toxicity index of 400 that inhibited 100% mycelial growth of the pathogen. Next in toxicity with toxicity index of 377.1 was carboxin + thiram. At 100 ppm carboxin + thiram exhibited 95.6% inhibition. Thiram and captan were noticed least effective. Five isolates of Trichoderma spp. were tested for their antagonistic properties against M. phaseolina by dual culture method. Significant variation in linear growth of the pathogen was observed in the presence of Trichoderma spp. T. viride-I was found to be most effective in controlling root rot which exhibited 71.1 per cent growth inhibition of the pathogen followed by T. harzianum - II while T. harizianum - III was found to be least effective in reducing the growth of pathogen.