In vitro evaluation of fungicides against Alternaria leaf spot of cotton

Cotton (Gossypium hirsutum L.) is the one of the most important commercial crops of the world, which belongs to the family Malvaceae. India is the largest cotton growing country in the world with an area of around 12.35 M ha followed by United States and China with production of 36.1 M bales and productivity of 524 kg lint/ha. Cotton crop is known to suffer from number of fungal, bacterial and viral diseases. Cotton is under constant threat of foliar diseases viz., grey mildew, Alternaria leaf spot, Myrothecium leaf spot, bacterial leaf blight, rust etc. Among them, Alternaria leaf spot caused by Alternaria spp. is predominant in causing economic losses to the cotton crop in the country. Evaluation of systemic, non-systemic and combined fungicides under in vitro conditions revealed that the among eight fungicides evaluated against Alternaria macrospora (N2A isolate), Propiconazole, Hexaconazole and Tebuconazole @ 500 and 1000 ppm recorded maximum inhibition with 100 per cent inhibition and no radial growth of mycelium was observed. Pyraclostrobin and Azoxystrobin @1000 ppm showed 91.0 and 87.2 per cent inhibition respectively. Carbendazim+Mancozeb (SAAF) @ 1500 ppm and 2000 ppm showed 96.1 and 96.9 per cent inhibition respectively.