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Sooty blotch (SB) and flyspeck (FS) is a disease complex which causes the blemishes on skin surface of apple (Malus domestica Borkh) and damages the cosmetic look of fruit in humid temperate areas of the world. Not only it affects the postharvest quality of apple fruits but also reduces the storage life due to increased transpiration. During this study, five different organic fungicides (Ridomil gold, Thiophanate-methyl, Metalaxyl + Mancozeb, Dithane M-45 and Benomyl) at the rate of 5g/l were sprayed on mature and healthy apple trees to control this disease. Fungicides were applied with spray schedule of 15 days interval. Eight sprays were applied from the month of June to September. Results obtained revealed that the application of organic fungicides significantly (P ≤ 0.05) reduced the disease incidence of SB and FS as compared to control. Maximum disease control (92.50%) and minimum (7.50%) fruit blotches were recorded with a combined application of Metalaxyl + Mancozeb. Similarly, maximum fruit weight (140.57 g), and total yield per tree (28.30 kg) were obtained in plants treated with Metalaxyl + Mancozeb. However, maximum fruit set per tree (299.75) was recorded in plants sprayed with Dithane M-45 as compared to control (160.25). Maximum total soluble solids and total sugars (12.90%, 15.50%) were recorded in fruits which were sprayed with Benomyl and Dithane M-45, while minimum total soluble solids and total sugars (10.90%, 10.87%) were recorded in control fruits. Minimum ascorbic acid and titratable acidity (15.10 mg/100 mL, 3.65%) were recorded in fruits which were treated with Benomyl, respectively. Overall, a combined treatment of Metalaxyl + Mancozeb not only gave the best control against SB and FS but also increased the total fruit yield and improved the fruit colour as compared to other treatments. Therefore, it could be further exploited on a commercial scale against SB and FS in future.
Keywords: Ascorbic acid; Disease complex; Malus domestica Borkh; Organic fungicides