Fruit trees - Knowledgebase Question

Toms River, Ne
Question by gtrommer
June 2, 2010
I have rust spots on the leaves of the apple tree. What causes that and how can this be contolled?

Answer from NGA
June 2, 2010


Many fungi can cause spots on apple leaves. Apple scab, cedar apple rust, hawthorn rust, and powdery mildew cause spots on leaves. If the areas are raised and a rusty color, and you can see powdery rust colored spores, it is classified as a rust disease. However, if the leaves have a rusty coloration that is not raised, the problem may not be a disease but a reaction of the leaves to physical injury. It's really difficult to diagnose without seeing the problem first hand. To avoid diseases, your apple trees can be sprayed with Bordeaux (lime-sulfur). This fungicide must be applied early and thoroughly to protect new growth. Apply according to label directions; as the buds break until the leaves are fully expanded. Do this at prepink, pink, calyx, and first cover. Since the fungus overwinters in fallen leaves and fruit, be sure to thoroughly clean up and dispose of plant debris in the fall months. Hope this answers all your questions.

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