Rhizoctonia solani, Fusarium oxisporum, Phytophthora colocasiae and Pithium sp. are the most important phytopathogens responsible for damping off diseases of vegetable crops like Tomato, Cabbage, Brinjal and Sugar beet. The inhibitory effect of three species of Trichoderma and Pseudomonas on the population of the target damping off pathogens like R. solani, F. oxisporum, P. colocasiae and Pithium sp. in soil was studied in vitro. Uniform quantity of inoculums (1g/kg dry soil) of the above pathogens isolated from infected Tomato rhizosphere were added in sterilized soil and maintained in plastic pots. Three species of Trichoderma viz. T. viride, T. harzianum, T. pseudokoningii and fluorescent pseudomonas, Pseudomonas fluorescens were inoculated as treatment in soil containing pathogens. The combined effect of all the bio-control agents was also evaluated. The population of R. solani, F. oxisporum, P. colocasiae, Pithium sp and Pseudomonas fluorescens was determined by soil dilution plate method. Reduction in population of R. solani, F. oxisporum, P. colocasiae and Pithium sp by T. viride is 72.53, 89.83, 87.77 and 67.16%. The same value for T. harzianum and T. pseudokoningii is 88.83, 61.16, 79.38, 61.66 and 71.50, 63.81, 81.56, 90.66% respectively. Pseudomonas fluorescens can control the above pathogens inhibiting their population up to 68.50, 90.50, 92.62, and 88.83% in soil. The combined treatment of all the bio-control agents is more effective than that of individual after 45 days of treatment. But in initial stage of treatment the combined effect was less effective. This may be due to the antagonistic effect between P. fluorescens and Trichoderma species in the multiplying stages in soil.
