A wet spring, a damaged apple and a sunken bark patch call for different first checks. This is an international temperate-garden guide: local bud break, frost and rainfall dates vary, so locate the sign on a leaf, fruit, bark or shoot before acting.
Start with where the sign sits
Photograph the whole tree and the affected part before removing material.
- Leaf: olive scab spot; note recent wet weather.
- Fruit: brown rot; remove the fruit and look for a wound.
- Bark: sunken canker; mark its edge before a major cut.
- Shoot: white powder; remove only a clearly infected tip.
Apple scab: dark marks after leaf wetness
Apple scab produces olive-green to dark scabby marks on leaves and fruit, and survives winter on fallen leaves and infected twigs, according to RHS.
A single bark wound is not this leaf-and-fruit pattern: compare both organs, look for the scabby surface and note recent wetness before clearing leaves.
- Clear fallen leaves where practical and record when new marks appear.
Apple canker: a bark wound needs a measured response
Apple canker causes sunken dead bark and infection often starts at wounds or buds. RHS advises cutting infected bark and wood back to fresh green tissue only when the diagnosis and cut are clear.
Unlike scab, canker is followed at a bark edge rather than a leaf mark; an expanding trunk edge is the reason to pause and seek local advice before a structural cut.
- Seek local help before removing a large stem or main branch.
Brown rot: injured fruit is the usual starting point
Brown rot is a spreading fungal rot of apples and can develop from wounds made by birds, insects or apple scab, as described by RHS.
A brown apple does not prove brown rot throughout the tree: first look for broken skin, then keep that fruit separate from a sunken bark lesion.
- Remove rotten fruit and hanging fruit mummies promptly.
Powdery mildew: white fungal growth on young shoots
Apple powdery mildew produces white fungal growth on young leaves, buds and shoots. RHS notes that the characteristic growth, not pale colour alone, helps distinguish it.
White growth on one young tip does not explain fruit rot or a bark wound; inspect nearby buds before deciding whether a small tip removal is enough.
- Check the same shoot tips as buds open next season.
Not every change is disease
Frost can damage blossom and young fruitlets without infection.
Yellowing can also follow waterlogging, drought, compaction, root trouble or nutrition, so leaf colour alone is not a nutrient diagnosis.
- Check soil moisture and drainage before adding fertiliser.
Prevent pressure with hygiene and a workable canopy
Remove infected leaves and fruit to reduce local scab sources.
RHS notes that apple cultivars can differ in powdery-mildew symptom severity.
This does not promise a disease-free tree.
- Keep notes on the cultivar and repeated symptoms.
Seasonal checks for temperate gardens
- At spring leaf emergence: check new leaves after prolonged wetness.
- During fruit growth: remove fruit that begins to rot.
- After harvest: remove mummies and record the first symptom date.
Frequently asked questions
Does every dark spot mean scab?
No; compare leaf and fruit symptoms and note the wet-weather pattern.
Should I remove fruit mummies?
Yes, remove clearly rotten fruit and mummies from the tree.
Can I prune apple canker?
Only with a clear diagnosis; ask locally before a large cut.
Is white growth powdery mildew?
Look for the characteristic white fungal growth on young shoots and leaves.
Is frost an infection?
No; frost timing and the affected flowers or fruitlets are useful clues.
Next step
Record the date, weather, cultivar and affected tree part. That comparison is more useful than naming a disease from one mark.
RHS describes apple scab as olive-green to dark scabby marks on leaves and fruit that survive winter on fallen leaves and infected twigs. That is why leaf litter belongs with leaf-and-fruit symptoms, not with a separate bark wound or a single pale shoot.
- Ask a local horticultural adviser about an expanding trunk wound.
Questions and answers
Does every dark spot mean scab? No; compare leaf and fruit symptoms and note the wet-weather pattern.
Should I remove fruit mummies? Yes, remove clearly rotten fruit and mummies from the tree.
Can I prune apple canker? Only with a clear diagnosis; ask locally before a large cut.
Is white growth powdery mildew? Look for the characteristic white fungal growth on young shoots and leaves.
Is frost an infection? No; frost timing and the affected flowers or fruitlets are useful clues.