Efficacy of Different Fungicides in the Control of Apple Powdery Mildew, Podosphaera leucotricha

Powdery mildew is one of the most important diseases of apple globally and is caused by the fungus Podosphaera leucotricha. The aim of this study was to determine the efficacy of the fungicides Boscalid + Pyraclovastrobin (Bellis®; WG, 38%) with the doses of 0.4, 0.7 and 1 ml L-1 compared with the fungicides Tri-floxystrobin + Fluopyram (Luna Sensation®; SC, 500) with the dose of 0.2 ml L-1, Tri-floxystrobin (Flint®; WG, 50%) with the dose of 0.2 ml L-1 and Tri-floxystrobin + Teboconazol (Nativo®; WG, 50%) with  the dose of 0.2 ml L-1 to control the apple powdery mildew disease. The experiment was carried out in Ardabil province in a randomized complete block design (RCBD) with 8 treatments and 4 replications in 2019-2020. Control treatments were with water spraying and without any spraying Treatments were applied in the spring in three stages (full green bud stage, pink flower stage and 10 days after the 2nd spraying). Ten days after the first symptoms of the disease were observed in the control treatments, samples were taken from the sheets and the disease incidence and disease severity percentages were calculated. The results showed that the highest rate of control (80%) of apple powdery mildew disease was related to Luna Sensation® (0.2 ml L-1). Then   the fungicide treatment of Bellis® (1 ml L-1) had the highest rate of control of the disease (76%) and the treatments of Flint® (0.2 ml L-1), Bellis® (0.7 and 0.4 ml L-1) and Nativo® (0.2 ml L-1) were ranked next in this regard. The efficacy of the new fungicide Bellis® at the rates of 1 and 0.7 ml L-1 was 76 and 60%, respectively. Since both the doses of Bellis® are effective in controlling the disease, therefore, to protect the health of the fungicide users, the consumers  of the products and the environment as well as reduction in costs, the preferred dose was chosen as 0.7 ml L-1.