Gadenin日本語Get the appLook at the tree in the right three places
Almost everything that goes wrong with this tree announces itself in one of three places, and a two-minute inspection of all three once a week through the growing season catches nearly all of it early. Look at the tips of the new shoots, at the junctions and wounds on the older wood, and at the fruit as it swells.
The tree is a stone fruit and shares the stone-fruit troubles: bacterial canker and silver leaf entering through cuts, brown rot on the fruit, aphids on soft growth, and boring insects in the trunk and fruit. What it does not share is the timing, because it flowers in midwinter, so the flowers themselves are largely out of reach of the insects that damage blossom on later-flowering fruit.
The single most useful preventive measure is one you have already read about under pruning: cut in summer, in warm dry weather, never in a wet winter. A very large share of the serious disease on this tree walks in through a winter pruning wound.
| Problem | What you see first | When | What to do |
|---|---|---|---|
| Aphids | New shoot tips curled and sticky, colonies packed under young leaves | From leaf out through early summer | Wash off with a hard jet of water, pinch out badly curled tips, leave predators alone |
| Bacterial canker | Sunken patches on limbs oozing amber gum, leaves above wilting | Visible any time, worst after wet winters | Cut the limb out well below the canker in dry summer weather, burn the prunings |
| Silver leaf | A silver sheen on the leaves of one limb, brown staining inside the cut wood | Symptoms show in the growing season | Remove the affected limb back to clean unstained wood, prune only in summer thereafter |
| Brown rot | A brown spreading patch on a fruit, later with pale rings of spores | As fruit swells and ripens | Pick off and destroy every affected fruit; never leave mummies hanging on the tree |
| Fruit borers | A small entry hole with gum or frass at it, fruit dropping early | From fruit set onward | Pick up and destroy all drops; thin the crop so fruit are not touching |
| Scale insects | Small fixed brown or white bumps along stems, sooty mold below | Noticed in dormancy, active in early summer | Rub off by hand on small trees, cut out badly encrusted twiggy wood in summer |
| Trunk borers | Coarse sawdust-like frass at the base of the trunk, a hole beneath it | Mostly midsummer onward | Probe the tunnel with a wire, keep the trunk base clear of weeds and mulch |
Aphids, and why you should be slow to spray
Aphids arrive as the leaves unfold and colonise the soft shoot tips, curling the leaves around themselves so that a spray cannot reach them anyway. On an established tree they are a cosmetic problem rather than a real one: the tree grows through them, and the curled leaves stay curled but the wood beneath ripens normally. On a one or two year old tree they matter more, because they can check the growth you need to build a framework.
The reason to be slow with insecticide is that the predators arrive two to three weeks after the aphids do, on their own schedule, and a spray at that moment kills the ladybird larvae and hoverfly larvae that were about to solve the problem for you for the rest of the season. Knocking colonies off with a hard jet of water and pinching out the worst tips buys those two weeks without breaking anything.
The one aphid symptom worth acting on quickly is sooty mold, the black film that grows on the honeydew the aphids drop. It does not attack the tree, but it blocks light from the leaves it coats and it tells you the colony has been there long enough to matter.
Canker and rot: the diseases you prevent rather than cure
Bacterial canker and silver leaf are the two that actually kill limbs, and neither has a cure once it is in the wood. Both enter through wounds, and both are far more active in cool wet conditions than in warm dry ones. Everything you can do about them is done with timing and hygiene rather than with a bottle.
- Prune only in summer, in dry weather Wait for a spell of warm dry days after picking. Cuts made then callus over within weeks, while cuts made in a wet winter sit open for months in exactly the conditions the spores prefer.
- Never leave a stub Cut back to the branch collar or to a bud. A stub has no way to seal, dies back, and becomes a dead entry point pointing straight into a living limb.
- Clean tools between trees Wipe blades with alcohol before moving from a tree you suspect to a healthy one, and certainly after cutting out a canker. This is how silver leaf most often travels from one tree to another in a garden.
- Cut infected wood out generously Take an affected limb back well beyond the visible symptom into clean unstained wood, checking the cut face as you go. Cutting close to the damage almost always leaves infection behind.
- Remove every mummy Fruit that rotted and dried on the tree carries brown rot straight into next season. Pick every mummified fruit off in dormancy, when they are easy to see on bare wood, and destroy them rather than composting.
- Keep the base of the trunk clear and dry Pull mulch and weeds back a hand's width from the trunk. A permanently damp trunk base invites canker and hides the frass that tells you a borer is at work.
Fungicide will not cure canker or silver leaf, and painting wound sealant over a cut has been shown to trap moisture and make matters worse rather than better. Leave clean cuts open to dry.
The fruit itself, and the choice to give up on a limb
Because the fruit is destined for processing and not for the fruit bowl, minor skin blemishes do not matter. What does matter is anything that opens the fruit: a borer hole, a split from uneven watering, or a brown rot patch. Any of those spoils the batch it goes into and spreads to sound fruit stored beside it, so cull at picking rather than at the kitchen table.
Thinning is a disease measure as much as a size measure. Fruit spaced 2 to 3 inches (5 to 8 cm) apart dries after rain and does not pass rot to its neighbor by contact, which is the main way brown rot moves through a crop.
Know when to stop trying. A limb with canker running into the main trunk, or a young tree with silver leaf staining in the trunk wood itself, is not going to be saved by careful pruning, and keeping it means keeping a source of infection next to your other trees. Take it out in dry summer weather, burn it, and replant elsewhere in the garden rather than in the same hole.
The record that turns symptoms into a pattern
Single observations are almost useless with pests and diseases; patterns across seasons are what let you act early. Note the date you first see aphids each year, the date you first see a bored or rotting fruit, which tree and roughly where on it, and what you did about it.
After two seasons that record tells you your own dates, which are often two or three weeks away from any general guidance because they depend on your site. Knowing that borers show up in your garden a fortnight after fruit set means you thin and clear windfalls before the damage rather than after it. Note the position of a canker on a limb as well, so that when you inspect the following summer you can see whether it has advanced or stalled.