Gadenin日本語Get the appPeach leaf curl: the fight is over before you see it
The leaves emerge thick, puckered and blistered, flushed red or purple, and then turn white with spores and fall. Almost everybody meets this in their first spring and reaches for a spray, and by then it is too late. The infection happened weeks earlier, while the buds were still tight and it was raining.
The fungus overwinters in the bark and in the bud scales. Its spores are moved only by water, and they can only get into a bud while that bud is wet and the temperature is somewhere between 45F and 60F (7C and 16C). Cool wet weather in late winter and very early spring is exactly the condition it needs. Once the leaves are out and open, the tree can no longer be infected for that year, and nothing you apply to a curled leaf will straighten it.
So the whole strategy is to keep rain off the buds through late winter and early spring. That is not a spray. It is a physical cover.
How to keep the rain off
The cover goes up before midwinter, before the first spores can be splashed, and comes down when the tree is in full leaf and settled weather has arrived, usually mid to late spring. The sides stay open: you are shedding rain, not building a greenhouse, and closing the sides both cooks the tree and shuts out the insects that pollinate it.
- On a fan-trained tree, build a lean-to Fix battens to the wall above the tree and run a sheet of clear polythene from them out and down to a frame 18 inches (45 cm) clear of the branches at the bottom. Leave both ends wide open. This is the reason a wall-trained peach is so much easier to keep clean.
- On a free-standing tree, build a tent Four canes or posts and a clear sheet tied over the top, sloping so water runs off one side, is enough. It must stand well clear of the branches, because any bud touching wet plastic gets infected through the plastic.
- On a potted tree, move it The simplest answer of all. A dwarf peach in a large pot spends late winter in an unheated porch, a carport or against a sheltered wall under an overhang, and comes out when the leaves are open.
- Hand-pollinate while it is covered A covered tree flowers early and in still air, so few insects find it. Go over the open flowers every other day with a soft brush, working from flower to flower. Ten minutes twice a week through the flowering period is enough.
- Take the cover down at the right time Leave it on too long and the tree draws up soft and the aphids arrive. Once the leaves are fully out and the weather has settled, the cover has done its job for the year.
If curl has already appeared, pick off and bin the affected leaves as soon as you see them, before they go white and shed spores. Then feed the tree with a balanced fertilizer and keep it watered so it can push a second set of clean leaves. A tree that refoliates twice is exhausted, so thin the crop harder that year and plan the cover for the winter.
Brown rot, and the fruit you must not leave on the tree
Brown rot shows as a soft brown patch on a ripening peach that spreads within days and erupts into buff-colored rings of mold. Warm humid weather takes a whole crop in a week. It gets in through any break in the skin, which is why split fruit, hail damage and insect punctures matter so much.
The thing that keeps it going year to year is the mummy: a shriveled infected fruit that stays hanging on the branch all winter, holding thousands of spores ready for spring. Every mummy left on the tree is next year's outbreak. Take them all off in autumn, and pick up every fallen and rotting fruit under the tree as you go through the season.
Beyond sanitation, the useful measures are all about drying and spacing: thin properly so no two fruit touch, keep the center of the tree open so air moves through it, avoid overhead watering as the fruit colors, and pick promptly rather than leaving fruit hanging past ripeness.
| Problem | What you see | When it starts | What actually works |
|---|---|---|---|
| Peach leaf curl | Thick red puckered leaves that whiten and drop | Cool wet spells before the buds open | A rain cover over the tree from midwinter to late spring; remove affected leaves; feed the tree to refoliate |
| Brown rot | Brown spreading patches with buff rings on ripening fruit | Warm humid weather near harvest | Remove every mummy and fallen fruit; thin so fruit do not touch; open the center of the tree |
| Bacterial canker | Sunken dark patches on bark oozing amber gum; branches die back | Wet autumn and winter, entering through wounds | Prune only in the growing season; cut affected limbs back to clean wood well below the damage |
| Peach twig borer | Wilting shoot tips in early summer, gum at the entry hole | Shortly after growth starts | Snap off and remove wilted tips as soon as they appear; keep fallen fruit cleared |
| Aphids | Curled young leaf tips, sticky honeydew, black sooty mold | Flush of soft spring growth | Do not overfeed with nitrogen; wash colonies off with water; leave ladybirds and hoverflies alone |
| Split stone and cracked fruit | Fruit split at the stem end or the stone broken open | Uneven water while the stone is hardening | Water evenly through midsummer; thin early rather than late; mulch to steady the soil |
Bacterial canker, and why pruning season is a disease decision
Canker is the reason a peach is never pruned in winter. It shows as sunken dark patches on the bark, often with amber gum weeping out, and the branch above the patch produces small yellow leaves and then dies. Once it is round a limb, that limb is finished.
The bacteria are on the tree already and are moved by rain. They get in through wounds, and they are most active in the cool wet months, which is precisely when a winter-pruned tree is standing full of open cuts that will not callus. Prune in spring and summer instead and the tree seals its own wounds in days.
If you find canker, cut the limb out well below the visible damage, into clean white wood, and do it in dry summer weather. Sterilize the blade between every cut and burn or bin what you remove. Do not compost it and do not leave it lying by the tree.
A note on gum in general: peaches ooze gum for many reasons, including simple stress and injury, and a bead of gum on its own is not proof of disease. Gum coming out of a sunken, discolored patch of bark is a different matter and should be treated as canker.
The record that saves you a season
Write down the date you first see each problem, every year. First curled leaf, first rotten fruit, first wilted shoot tip. On its own it looks like trivia; over three seasons it becomes the only accurate calendar you will ever have for your own garden.
It matters most for leaf curl, because everything depends on acting before symptoms. Once you know the date the curl usually shows on your tree, you know the cover has to be up at least eight weeks earlier, and you stop guessing. Note the date you put the cover up and took it down as well, and whether curl appeared anyway; that tells you whether the cover was late, too small or touching the branches.
Record which branch each problem appeared on too. Canker and borers come back to the same limbs, and a note saying which side of the tree was affected last year is worth more than a general memory that the tree was not very well.