In-vitro evaluation of fungicides, bioagents and aqueous leaf extracts against Alternaria leaf blight of cotton

All the six fungicides viz., Mancozeb (75% WP); Carbendazim (50WP), Copper oxychloride (50WP), Captan (50 WP), Thiram (75 % WP), Chlorothalonil (75 WP) evaluated in vitro (@500, 1000 and 1500 ppm) were found effective against A. macrospora and caused significant inhibition of test pathogen over untreated control. However, Thiram was found most effective and recorded significantly highest mean mycelial inhibition (90.42%). This was followed by the fungicides, Captan (82.04%), Mancozeb (79.88%), Carbendazim(77.5%), Chlorothalonil (74.52%) and copper oxychloride (71.75%). All the five fungal and one bacterial bioagents/ antagonists evaluated in vitro against A. macrospora were found antifungal/ antagonistic against the test pathogen. However, T. viride was found most effective and recorded least linear mycelial growth (32.72 mm) with corresponding significantly highest mycelial inhibition (63.64%) of the test pathogen. The second and third best bioagents found were T. koningii and P. fluorescens, which recorded linear mycelial growth, respectively of 33.90 mm and 33.95 mm with corresponding mycelial inhibition, respectively of 62.33 and 62.27 per cent. All the six botanicals/plant extracts evaluated in vitro (@5, 10 and 15 % each) were found fungistatic/ fungicidal against. A.macrospora. However, significantly least mean radial mycelial growth (56.18mm) and significantly highest mean mycelial inhibition (37.47%) was recorded with Garlic. The second and third best botanicals found were onion and Tulsi which recorded second and third least mean radial mycelial growth, respectively of 58.52 mm and 62.51 mm with corresponding mean mycelial inhibition of 34.97 and 32.86 per cent, respectively.