Refinement of fungicidal spray schedule for effective management of potato late blight in north-western hill

Late blight of potato caused by Phytophthora infestans is endemic to Chuhar and Kangra valleys of Himachal Pradesh. The disease severity ranged between 88.6 - 97.1 per cent and 7.5 - 62.2 per cent in Chuhar and Kangra valley, where potato is grown as summer and spring crop, respectively. Disease severity was higher in spring crop grown in high hills as compared to summer potato grown in mid hills. Eleven fungicides viz. Ridomil MZ/Mateo/Unilax (metalaxyl 8% + mancozeb 64%) 72 WP, Kavach (chlorothalonil) 75 WP, Antracol (propineb) 70 WP, Indofil M-45 (mancozeb) 75 WP, Eurofil NT (mancozeb) 35 SC, Mancozeb 75 WDG, Indofil Z-78 (zineb) 75 WP, Curzate (cymoxanil 8% + mancozeb 64%) 72 WP and Blitox (copper oxychloride) 50 WP were evaluated against late blight under field conditions. Ridomil MZ and Mateo were found most effective and provided more than 80 and 70 per cent control of the disease at Chuhar and Kangra valleys, respectively. Among non-systemic fungicides, Kavach and Antracol were found better compared to Indofil M-45. The spray schedule consisting of Ridomil MZ followed by Kavach and Ridomil MZ was found highly effective with maximum disease control (72.5%) and higher yield (36.4%) over the unprotected control. The other spray schedules, i.e. spray of Ridomil MZ followed by Antracol and Ridomil MZ was also found equally effective in reducing the severity of disease and increasing the crop yield.