Fungicidal spray schedule for economical management of potato late blight in north-western hills of India.

摘要

Field trials were conducted for 3 years (1990-92) at the Potato Development Station, Phuladhar, Himachal Pradesh, India, to develop an effective and economical fungicidal spray schedule for late blight of potatoes (caused by Phytophthora infestans).The trials were planted with the blight susceptible cv. Kufri Chandramukhi and 4 fungicides (SAN 518 F 64 WP (oxadixyl 10% + copper oxychloride 54%), Ridomil MZ 72 WP (metalaxyl 8% + mancozeb 64%), Dithane M-45 75 WP (mancozeb), Kavach 75 WP (chlorothalonil)) were evaluated in 6 different combinations. Two sprays of Ridomil at 0.25% at 15-day intervals plus 4 sprays of Dithane 0.2% at 7-day intervals recorded the least disease compared with the untreated check but did not differ significantly from 1 spray of Ridomil plus 6 sprays of Dithane with respect to disease severity and infection rate. Sprays of Kavach were least effective. One spray of Ridomil plus 6 sprays of Dithane gave the highest cost-benefit ratio (1:6.30). It is concluded that during blight epidemic years 2 sprays of Ridomil at 15 day intervals in combination with 4 sprays of Dithane at weekly intervals should be applied for effective disease management but under normal disease pressure 1 spray of Ridomil and subsequent sprays of Dithane at weekly intervals should be adequate.