Apple scab is a very common disease, caused by a fungus that attacks the young leaves as soon as they emerge in spring. It grows on the leaves, producing spores. When the fruits form they are attacked too, small brown or black scabs being the result.
Apart from direct damage to the fruit, apple scab seriously weakens the tree, predisposing it to apple canker disease. Pears are affected by a similar scab disease, but less frequently. Apple scab is most severe in wet years and in localities with high rainfall.
Use resistant varieties such as ‘Discovery’, ‘Katy’ and ‘Lord Lambourne’. Spray susceptible varieties at bud-burst, in late March or early April, with Captan or Systemic Fungicide, such as Fungus Clear 2. Repeat the spray at least three times between then and the end of June. In a wet year, and in wet localities, more applications can be necessary.