In-vitro Assessment of Fungicides and pH Levels on the Mycelial Growth and Sclerotia Production of Sclerotium rolfsii Sacc. causing White Rot of Onion in Manipur

Seven fungicides and five different pH levels were evaluated against Sclerotium rolfsii Saccardo, causing white rot of onion in Manipur. The efficacies of the fungicides were evaluated by poisoned food technique on potato dextrose agar. The effect of different pH levels was evaluated on potato dextrose broth by measuring dry mycelial weight and counting the number of sclerotia produced by the fungus. Three fungicides, namely, Hexaconazole (500 and 1000ppm), Propiconazole (500 and 1000ppm) and Mancozeb (1000 and 2000ppm), resulted 100% inhibition of mycelial growth and sclerotia production of the white rot pathogen. The mycelial growth and sclerotia production of S. rolfsii were minimal in pH 4.0, providing a total of 0.62g of dry mycelial weight and 1069 sclerotia. The maximum mycelial growth of 0.76g was recorded at pH 5.0, followed by 0.72g at pH 6.0. Maximum number of sclerotia were produced at pH 7.0, followed by pH 6.6. and 6.0 successively.