Chemical management of marssonina leaf blotch and alternaria leaf spot diseases of apple in Himachal Pradesh

A number of leaf spot diseases attack apple, the most important temperate fruit crop in Himachal Pradesh. After the scab caused by Venturia inaequalis (Cooke) G. Winter, apple plantations in the state are under attack by relatively less known fungal pathogens Marssonina coronaria (Ellis & J.J. Davis) J.J. Davis (Syn. Marssonina mali (P. Henn) Ito) and Alternaria alternata (Fr.) Keissler by causing mid-season defoliation. Hence, to manage these diseases, fluopyram 200 + tebuconazole 200 SC along with standard checks were evaluated for bio-efficacy against Marssonina blotch and Alternaria leaf spot during 2015 and 2016. The pooled analysis of two crop seasons showed that all the treatments differed significantly with regard to per cent disease index and per cent disease control for both the diseases. For Marssonina blotch, maximum per cent disease control was observed when the crop was sprayed with fluopyram 200 + tebuconazole 200 SC at a concentration of 0.0625 per cent (94.35%) followed by fluopyram 200 + tebuconazole 200 SC at a concentration of 0.05 per cent (89.85%) and 0.0375 per cent (87.72%), respectively. For Alternaria leaf spot, maximum per cent disease control occurred when the crop was sprayed with fluopyram 200 + tebuconazole 200 SC at a concentration of 0.0625 per cent (94.55 %) followed by fluopyram 200 + tebuconazole 200 SC at its concentration 0.05 per cent (89.42%) and 0.0375 per cent (86.55 %), respectively.