Leaf Spot Disease of Onion Alternaria alternata (Fr.) Keissler

The leaf spot disease of onion caused by Alternaria alternata (Fr.) Keissler is the most serious one. The disease causes extensive damage to bulbs as well as seed crop. In view of the destructive nature of leaf spot of onion, the present investigation was planned to find out the effective disease management practices. Potato dextrose agar and host leaf decoction agar medium proved the best for growth and spore production by the fungus followed by oat meal agar, Czapeck¿s (Dox) agar and Richards¿ agar medium. Neem leaf and dhatura showed the maximum fungal growth inhibition and sporulation. While Trichoderma harzianum and T. viride to were proved to be the best antagonist against the pathogen. In vitro screenings Hexaconazole (Contaf 5 EC) was found the most effective and inhibited cent per cent growth of A. alternata even at 500 ppm concentration. Under field condition the minimum disease was recorded in foliar application of Hexaconazole (0.05 %).