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Cherry problems fall into wood diseases and fruit or foliage problems, and confusing them wastes years. Wood diseases, principally silver leaf and bacterial canker, get into the trunk and limbs through wounds and cannot be cured once established: the response is prevention through pruning timing and, when it is too late, removal of the affected limb or the whole tree. Fruit and leaf problems come and go annually and are managed by hygiene, airflow and timing.
Get into the habit of walking the tree once a fortnight through the growing season and looking specifically at bark and leaf color, not just fruit. Both wood diseases give a warning sign months before the branch dies, and a limb removed early can save the tree.
| Problem | First sign | Response |
|---|---|---|
| Silver leaf | Metallic sheen on leaves of one branch | Cut the limb out in summer, well below the stain in the wood |
| Bacterial canker | Sunken bark, amber gum, dying shoots | Remove affected wood in summer; never prune in winter |
| Brown rot | Brown fruit with buff pustule rings | Remove every affected fruit and mummy; improve airflow |
| Fruit splitting | Cracks after rain near ripeness | Even watering, rain cover, pick early |
| Blackfly / cherry aphid | Curled, sticky shoot tips | Squash or wash off; leave predators alone |
| Spotted wing fruit fly | Soft, collapsing fruit with tiny puncture | Pick clean, remove all fallen fruit, chill immediately |
Silver leaf: the reason you never prune in winter
Silver leaf is a fungus that colonises the wood and produces a toxin that separates leaf layers, giving the foliage a silvery, metallic look. It shows on one branch first, then spreads. Spores are released mostly in cool, wet conditions and infect through fresh wounds, which is exactly why winter pruning is the classic way to introduce it.
Confirm it before acting. Cut through an affected branch and look at the cross-section: genuine infection shows a dark brown or purplish stain in the heartwood. Silvering with no stain in the wood is usually false silver leaf, a stress response to drought or poor soil, and that recovers on its own with better watering and mulching.
Where the stain is present, cut the limb out in summer at least 6 inches (15 cm) beyond the last visible staining, checking each cut face until the wood runs clean. Burn or bin the prunings; do not leave them lying, and do not chip them for mulch. If the stain reaches the trunk, the tree is finished and the sooner it comes out the less it infects neighbors.
Bacterial canker
Canker shows as sunken, dark patches on the bark of trunk or limbs, usually with amber gum oozing from them. Above the lesion, shoots leaf out weakly in spring and then wilt and die as the affected area girdles the branch. Leaves may also show small round holes where infected tissue drops out, giving a shot-hole appearance.
Bacteria enter through wounds, leaf scars at leaf fall and pruning cuts, and the wet, cool part of the year is when they move. Prevention is the same discipline as for silver leaf: prune only in warm growing weather, make clean cuts outside the collar, keep the trunk free of mower and string trimmer damage, and stake dwarf trees so the bark is not being rubbed by ties or rocking.
Treatment is surgical. Remove affected wood in mid summer, cutting well back into clean tissue, and sterilize the blade before touching healthy parts of the tree. Trunk lesions on a small tree are usually fatal; a young dwarf tree with canker on the main stem is better replaced than nursed. Waterlogged soil and stress make trees markedly more susceptible, so drainage is part of the answer.
A tree that oozes clear gum without sunken bark is often just responding to physical injury or stress, not canker. Look for the sunken lesion and the dieback above it before condemning a limb.
Brown rot and split fruit
Brown rot turns ripening fruit brown and soft, then covers it with concentric rings of buff-colored pustules, and finally leaves a shriveled mummy hanging on the spur through winter. Those mummies are the source of next year's infection, which makes clearing them the single most effective control there is.
It enters through damaged skin, so it follows directly from split fruit, bird pecks and insect punctures. Managing splitting and netting properly cuts brown rot at the same time. Airflow matters too: an open, thinned canopy dries fruit faster after rain and infection drops accordingly.
Remove every affected fruit the moment you see it, including those on the ground, and take off all mummies during the summer prune. Bag them; do not compost. Fruit clusters that touch each other spread it fastest, so where a spur carries a dense cluster, thin it out while the fruit is small.
- Pick off rotting fruit immediately Every day during ripening, walk the tree and take off anything brown or split. One infected fruit left in a cluster will infect the fruit touching it within days.
- Clear fallen fruit from the ground Fallen fruit under the tree feeds both brown rot and fruit flies, whose numbers build through the season. Rake and remove it at every picking, not once at the end.
- Strip the mummies in summer During the summer prune, go over every spur and remove shriveled fruit still attached. This is the main carry-over route from one year to the next.
- Thin dense clusters early Where fruit sits shoulder to shoulder, remove a few while they are pea-sized. Fruit that is not touching does not pass rot along the cluster.
Aphids, fruit flies and the things not worth panicking about
Black cherry aphid colonises shoot tips in spring, curling the young leaves tightly and coating them in sticky honeydew that then goes black with sooty mold. It disfigures growth on young trees but rarely affects the crop on an established one. Squash colonies by hand or wash them off with a jet of water, and leave ladybirds and hoverfly larvae to finish the job. Do not spray anything while the tree is in flower.
Spotted wing fruit fly lays into sound, ripening fruit rather than waiting for damage, and the fruit collapses soft with a tiny puncture mark. The practical defenses are picking promptly at ripeness rather than leaving fruit hanging, clearing all fallen and overripe fruit, and refrigerating the crop straight away, which stops any eggs already present from developing.
Ignore some things. A few holes in leaves, some early leaf drop in a dry summer, and clear gum at a pruning cut are not emergencies. What justifies action is silvering foliage, sunken bark with dieback above it, and rot spreading through fruit clusters.
Keep a note of what appeared and when: the date aphids first showed on shoot tips, the date the first rotten fruit turned up, which limb silvered. Those first-sighting dates are what let you act a fortnight earlier next year instead of reacting after the damage.