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February 13, 2012
Apple Scab
What Is It?
Apple Scab is a disease that affects the leaves, buds, and fruits of apple and crabapple trees. Though apple scab doesn't kill a tree, years of early defoliation weaken it, making it prone to other problems. It also causes apple trees to produce fewer leaves, and less fruit.
What Causes It?
The fungus overwinters on dead leaves, and its spores are spread to other parts of the tree in the spring through rainfall and wind. When temperatures reach 40°F, the fungus becomes activated, and begins to infect the tree again. This cycle continues throughout the summer, until the leaves and fruit fall from the tree at the onset of winter.
What Does It Look Like?
Scab infections are usually noticed first on leaves, which may become twisted or puckered and have black or olive green, circular spots on the upper surface. Severely affected leaves then turn yellow and drop. Later in the season, scabby spots may be found on fruit, eventually causing distortion and cracking.
How Can I Control It?
To prevent apple scab from affecting your crabapple trees, select a scab resistant variety, such has ‘Red Jewel, ‘Prairiefire’, ‘Louisa’, or ‘Pink Princess’.
For crabapple trees already infected with Apple Scab, apply a fungicide like Fertilome Systemic Fungicide (Banner) at the rate of ½ tablespoon per gallon of water. Start applications when buds begin to appear around mid to late March. Apply once every two weeks for a total of six weeks. For the best results, cover the whole tree thoroughly, and don’t skip any applications.
For fruit bearing apple trees, follow the above spray schedule, and also apply a fruit tree spray for maximum control.
If the leaves still fall in the summer, collect and discard them, and plan on applying another application of fungicide next spring. In the fall, add some fertilizer to your apple or crabapple trees to increase their vigor.
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Just North of the Shoppes on Route 91 | 309.691.4561 | Contact Us
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