Management of Alternaria blotch of apple using fungicides.

Studies on the efficacy of various systemic and non-systemic fungicides in controlling the Alternaria blotch (Alternaria mali) in apple were carried out both under laboratory conditions and at field levels. In vitro studies with nine systemic and non-systemic fungicides indicated that all the test fungicides significantly inhibited the mycelial growth of A. mali at all concentrations tested. Penconazole 10EC and hexaconazole 5EC proved significantly superior to all other fungicides exhibiting 72.6 and 71.8% mycelial growth inhibition, while carbendazim 50WP proved least effective (33.1%). Mycelial growth inhibition of the test fungus increased with the increase in their concentrations. Field evaluation of different fungicide treatments at three different concentrations for two years indicated that all the systemic and non-systemic fungicides at each level of concentration in each year significantly reduced the Alternaria blotch as compared to check. Among systemic fungicides, hexaconazole 5EC @ 0.05% was significantly superior (PDI 0.9%) in reducing the disease. Similarly, among non-systemic fungicides copperoxychloride (PDI 4.8%) and ziram (PDI 4.6%) both at 0.4% proved significantly superior in reducing the disease compared to check (PDI 25.6%).