In Vitro Evaluation of Phytoextracts and Bio Agents against Pathogen/S of Twister Disease of Onion

Twister disease of onion has become epidemic in coastal tract and other onion growing districts of Karnataka which caused heavy loss and its causal agents are C.gloeosporioides I and F. oxysporum. Onion suffers from pest and fungaldiseases but the fungicides cause pollution and disturb microbial balance of the soil. Under integrated fungaldisease management programme cost effective and ecofriendly component like plant extracts are used to control plant pathogens Therefore efforts were made to screen plant extracts and bio agents under laboratory condition. Botanicals in consortia of plant extracts (Azadirachta indica, Prosopis julifera, Clerodendron inerme and Parthenium hysterophorus) was studied by food poisoning techniquie and other biocontrol agents by dual culture. In vitro tests showed that there were significant differences between the inhibitory effects on the mycelial growth. Of the plant extracts evaluated T₁ (A. indica, P. julifera, C. inerme and P. hysterophorus in 1: 1: 1: 1) inhibited maximum mycelial growth of C. gleosporoides (46.66%) followed by T₅ (40.00%). T₅ (62.66%) inhibited maximum mycelial growth of F. oxysporum followed by T1 (56.66%). Among the seven bioagents evaluated four species of Trichoderma inhibited mycelial growth (78.00%) of C. gleosporoides. on F. oxysporum revealed that all the four fungal antagonists significantly reduced the growth of F. oxysporum either by over growing or by exhibiting inhibition zones, except bacterial bioagents.