In vitro effect of fungicides and phyto-extracts against Alternaria alternata causing leaf blight of groundnut

Abstract

Leaf blight caused by Alternaria alternata (Fr.) Keissler was observed on leaves of groundnut (Arachis hypogaea L.).The fungus was isolated from infected leaves and observed to be pathogenic under artificial inoculation conditions. Among plants extract, garlic clove extract was most effective in inhibiting the mycelial growth and sporulation of Alternaria alternata, followed by neem and datura leaf extracts. Babul leaf extract was not inhibiting the mycelial growth and sporulation of the fungus in poisoned food technique. Mancozeb at 1000 ppm resulted complete inhibition of mycelial growth and sporulation, followed by copper oxychloride and Captaf. Propiconazole was least effective followed by captan and chlorothalonil. Groundnut (Arachis hypogaea.L) is mainly grown as an oilseed kharif crop in India, but considerable quantities are used directly for human consumption like other pulses. The kernels are widely acknowledged as a rich &cheap source of vegetable protein. The chemical composition of the kernels indicating their value as food with: protein 25.33, carbohydrates 10.20, fat 40.50, fibre3.4, & ash 1.9 percent. A principal limiting factor in profitable cultivation of this crop in Rajasthan is the attack of several diseases mainly caused by fungi which cause heavy crop losses at all the stages, right from sowing to harvest and storage. The diseases which affect the foliage cause extensive damage to tissues involved in photosynthesis, and hence, result in yield losses. Leaf blight caused by Alernaria alernata is an important disease in the major groundnut growing areas of the state. The disease appears as small oval discolored lesions scattered irregularly on the leaves these spots become irregular in shape with increase in size and appear brown to grey in colour with yellow zone surrounding the spots. In the disease occurs widely in the crops grown in sandy soil in the Rajasthan, where weather conditions are dry, and temperature remains high. Under favourable conditions, spread of disease is rapid involving all the plants in a field and such blighted plants can be recognized from a distance. Keeping in view the importance of the disease, the present study was conducted during 2006-07 to evaluate in vitro efficacy of some phyto-extracts and systemic as well as non-systemic fungicides against Alternaria alternate