Bioefficacy of some plant extracts and biocontrol agents against Alternaria solani and their compatibility

Saprophytic fungi isolated from tomato phylloplane and some plant extracts were evaluated against Alternaria solani, the causal agent of early blight of tomato, under laboratory and screen house conditions. Among antagonists assayed in vitro, Trichoderma viride, T. harzianum and Bacillus subtilis were found inhibitory to A. solani. Among the plant extracts tested in vitro, cold aqueous extracts of Clerodendrum aculeatum and Azadirachta indica showed maximum inhibition of mycelial growth of Alternaria solani. Foliar spray of Clerodendron leaf extract (15%) immediately after appearance of symptoms or foliar spray of T. viride (107 cfu/ml) 24 h before challenge inoculation with the test fungus was found effective in reducing the disease severity under screen house conditions. Further, an in vitro experment was conducted to study the compatibility of bioagents and plant extracts for their possible use in integrated disease management. The bioagents; T. viride, T. harzianum and Gliocladium virens were found to be compatible with Clerodendron leaf extract at a concentration of 15 per cent. Hence, there is a scope to integrate Clerodendron leaf extract and bio-agents for eco-friendly management of early blight of tomato.