Plant Disease Research

Fungicides metalaxyl (Krilaxyl 35WS, Apron 35DS), ofurace 50WP, propamocarb hydrochloride (Previcur N), chlorothalonil 80WP (Kavach), mancozeb 75WP (Indofil M-45), Bordeaux mixture, 4:4:50 (True), copper oxychloride 50WP (Blue copper), phenyl mercury acetate (Emisan-6), thiram 75 WS and co-ordinate mixtures of metalaxyl 8% + mancozeb 64% (Ridomil MZ 72WP, Unilax 72WP) and ofurace 6% + mancozeb 64% (Patafol 70WP) were field evaluated through corm dip treatment and foliar spray against leaf blight (Phytophthora colocasiae) of taro (Colocasia esculenta). Corm dip for half and one hour before sowing in suspension of test fungicides delayed the initiation of disease by 6–10 days, best being corm dip in Ridomil MZ followed by Indofil M-45 and Apron in checking the disease and increasing the corm yield. Three fortnightly foliar sprays of Ridomil MZ @ 0.25% with or without sticker were found highly effective in checking the disease. Ridomil MZ when sprayed on lamina and petiole gave best control of disease in contrast to sprays made either on lamina or petiole. Sprays of Ridomil MZ resulted in 35.50 to 85.76% control of disease with 38 to 192% increase in yield. Integration of corm dip in Ridomil MZ @ 0.25% for 1 hour before sowing followed by three fortnightly sprays of Ridomil MZ gave best control of the disease. The disease caused 22.71 to 64.36% loss in crop yield depending on its severity and disease control achieved with corm dip and chemical means increased the corm yield by 18.67 to 180.57per cent. A unit increase in disease control caused 0.1918 units increase in corm yield.