Biocontrol of damping off of tomato caused by Pythium aphanidermatum

ABSTRACT: Damping-off of tomato caused by Pythium aphanidermatum was reduced by the application of talc based formulation of Trichoderma viride and Pseudomonas fluorescens in nursery beds before sowing. Besides reducing the pre- and post-emergence damping off these antagonists ' increased the root length, shoot length and biomass produ~ion of tomato seedlings. These antagonists significantly reduced the population of P. aphanidermatum in soil. Key words: Damping off, Pythium aphanidermatum, biocontrol, Trichoderma viride, Pseudomonas fluorescens Tomato, an important vegetable crop is attacked by several diseases, caused by fungi, bacteria and vi-ruses leading to severe crop losses. Among the fungal diseases, the damping off incited by Pythium aphanidermatum in nurseries is a major constraint in the production of tomato. Pythium spp. are essentially soil borne (Berkley, 1925; Horsfall, 1930) and pose a greater problem in disease management. The most com-mon means to check the disease in nurseries is by using fungicides but frequent and indiscriminate use of fun-gicides often leads to atmospheric pollution and devel-opment of fungicide resistance in pathogens. In this context, biological control is coming up as an alterna-tive strategy for disease management which is also ecology- conscious and environment friendly. Several organisms have been successfully used as biocontrol agents, such as Trichoderma spp. (Raguchander et al., 1997), Bacillus spp. (Copper and Campbell, 1986) and Pseudomonas spp. (Vidhyaksekaran and Muthamilan, 1995). In the present study, attempts were made to assess the effect of talc-based formulations of Tricho-derma viride and Pseudomonas fluorescens on damp-ing off and seedling growth of tomato and soil popu-lation of Pythium aphanidermatum under field condtions.