Why it happens
Apple scab is caused by the fungus Venturia inaequalis. It infects leaves and fruit during cool, wet periods in spring and early summer. The fungus survives on fallen leaves and releases spores when spring weather stays wet long enough.
What to check next
- Are spots on both leaves and fruit, or mostly one?
- Did wet weather coincide with early leaf emergence?
- Is the tree a scab-susceptible variety?
- Are fallen leaves still under the tree from last year?
When to get more help
Ask for local help if scab is severe several years in a row, if young trees are losing most of their leaves, or if you are unsure whether a product is labeled for your situation.