Management of late blight of potato through chemicals

Efforts made in the present investigation to evaluate few commonly used fungicides for their comparative efficacy against Phytophthora infestans (Mont.)deBary-the incitant of late bight, with a view to select the most effective fungicide for the management of the disease.Among the seven fungicides, two fungicides namely Cymoxanil 8% + Mancozeb 64% and Dimethomorph 50% were found most effective in pot evaluation which could reduce the disease to an extent of 99.98% and 99.95%, respectively when applied before appearance of disease.The same fungicides could protect 99.84% and 99.69% of the crop when applied after 1% appearance of the disease.The best two fungicides, Cymoxanil 8% + Mancozeb 64% and Dimethomorph 50% were selected to compare their relative efficacy with the existing recommended fungicides Metalaxyl 8% + Mancozeb 64% and Mancozeb 75% under field condition.The highest protection (100 %) against late blight with a corresponding maximum yield (73.20 q/ha) was recorded in the treatment of one prophylactic spray with Cymoxanil 8% + Mancozeb 64% followed by two additional spray with same fungicide at 10 days interval.Metalaxyl 8% + Mancozeb 64% when applied as one prophylactic spray followed by two additional sprays at 10 days interval could protect 97.64 % crop with a production of 62.60 q of healthy tuber per ha.