To Evaluate the Efficacy of the Fungicide tetraconazole against Apple Powdery Mildew (Podosphaera leucotricha Ellis. & Everh.)

Apple powdery mildew is one of the most important fungal diseases in the world and on some cultivars in Iran. In order to evaluate the efficacy of the fungicide tetraconazole for the control of apple powdery mildew an experiment was conducted on a susceptible cultivar (Golab) in the orchards with previous records of the disease on trees with similar age and conditions ofcultivation in Isfahan and Khorasan-Razaviprovinces. The experiment was performed in a randomized complete blocks design with 6 treatments and four replications. Treatments included fungiciedes, kresoxim-methyl (Stroby® WG 50%), 0.2 g/1000 L, trifloxystrobin (Flint® WG 50%), 0.2 g/1000 L and tetraconazole (Domark® EC 100), 0.2, 0.25, 0.3 ml/1000 L and control. Fungicides were applied at three stages of pink buds, mid of blooming and at the end of the flowering period. Five new shoots were collected from each tree in the treated plots twenty days after the last fungicide spraying and were placed in plastic bags. All the leaves from each replication were removed from the branches collected and were mixed in a dish, and hundred leaves were chosen randomly and the percent incidence and severity of the infection was evaluated. The results obtained in Isfahan and Khorasan Razavi provinces were analyzed statistically by analysis of variance and it is observed that the effect of the treatments (fungicides) on the incidence and severity of powdery mildew infection were significant. The results show that all the treatments with the fungicides have decreased the severity and incidence of infection significantly compared with the control. The results obtained in both the regions show that Domark (0.3 ml/1000 L) fungicides had the best effects in controlling apple powdery mildew. Therefore Domark with the concentration of 0.3 ml/1000 Lcould be recommended for control of apple powdery mildew.