Fallen Leaves and Scab — What to Do in Autumn
Scab is one of the most common diseases of apple and pear, and much of next spring’s risk is decided this autumn by what you do with the fallen leaves. This page explains where the disease overwinters, how it spreads in spring and what to do now. The sources are listed at the bottom; this is general background and does not replace looking at your actual tree.
At a glance
- Where it overwinters
- Mainly in infected leaves on the ground.
- When spores are released
- During rainy spells in spring, when leaves get wet.
- Fastest infection
- At about 13–24°C (55–75°F); initial infection needs at least 9 continuous hours of leaf wetness.
- Dry spring
- If spring is dry from green tip through fruit set, scab is usually not a problem.
- What to do now
- Collect and destroy fallen leaves in autumn or winter, or chop them with a mower.
- A single tree
- On a single backyard tree, removing the dropped leaves alone can keep scab at tolerable levels.
- Watering
- If sprinklers wet the leaves, irrigate between sunrise and noon so they can dry.
- Highest-risk period
- From green tip until 1–2 weeks after petal fall.
Where scab overwinters
The scab fungus overwinters mainly in infected leaves that have fallen to the ground. In winter and early spring it forms fruiting bodies in them. On pear it can also overwinter in lesions on twigs, especially in high-rainfall areas.
How it spreads in spring
During rainy spells in spring, spores are released from the fallen leaves and carried by wind and splashing water to developing leaves, flowers and fruit. Primary infections can occur from green tip until 1–2 weeks after petal fall, and symptoms appear 1–2 weeks after infection.
Infection is fastest at about 13–24°C, when leaves or fruit need at least 9 continuous hours of wetness. Secondary spores later form on the lesions (8–17 days after primary infection) and spread the disease through the season during rain. If spring is dry from green tip through fruit set, scab is usually not a problem.
What to do with the fallen leaves
- Collect the fallen leaves in autumn (or winter) and destroy them.
- Alternatively, chop them with a mower.
- On a single backyard tree, removing the dropped leaves alone can keep scab at tolerable levels.
- With several trees, especially in cooler, wetter areas, additional steps may be needed.
What else helps
- If sprinklers wet the leaves, water between sunrise and noon so they can dry. Lowering the sprinkler angle also limits foliage wetting.
- Some apples are highly resistant to scab, and so are some crabapples. Asian pears are less susceptible than European pears. When you plant a new tree, ask the nursery about the variety’s resistance.
When the risk is highest in spring
Watch the rainy spells from green tip to fruit set. Keep a note of rainfall and how long the leaves stay wet — that is the main warning sign.
Common questions
Why are fallen leaves a problem for apple trees?
Because the scab fungus overwinters mainly in infected leaves on the ground. In spring, rain releases spores from them that infect new leaves, flowers and fruit.
What should I do with fallen leaves?
Collect them in autumn (or winter) and destroy them, or chop them with a mower. On a single tree, removing the dropped leaves alone can keep the disease at tolerable levels.
When is the scab risk highest?
From green tip until 1–2 weeks after petal fall, in rainy weather. Infection is fastest at about 13–24°C, when leaves stay wet for at least 9 continuous hours. If spring is dry, scab is usually not a problem.
Does this apply to pears too?
Yes. Pear scab is closely related: it overwinters mainly in fallen leaves, and in high-rainfall areas also in lesions on twigs. Asian pears are less susceptible than European pears.
How should I water so I do not help the disease?
If sprinklers wet the leaves, water between sunrise and noon so they can dry. Lowering the sprinkler angle also limits foliage wetting.
Are there apples that do not get scab?
Some varieties are highly resistant to scab. When you plant a new tree, ask the nursery about the variety’s resistance.
Important: This page is general background for a home garden and does not replace an on-site look or a specialist's advice. It names no spray products: for crop protection, always follow the product label and the rules in force.
Related calendars
More seasonal tips
Sources
This page was checked against the public reference below. It is general background, not a diagnosis of a specific plant.
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