Gadenin日本語Get the appStart from the fact that it is a healthy tree
Compared with apple, pear or common quince, Chinese quince is remarkably free of trouble. It is not much bothered by scab, it rarely defoliates from leaf disease, its bark shelters no particular pest, and in a normal garden year an established tree needs no spraying and no intervention of any kind. If you came to it expecting the disease calendar that goes with growing apples, you can put that aside.
The reason to say so plainly is that it changes how you should respond to the occasional blemish. A few spotted leaves, some lichen on the trunk, a handful of aphids on the spring flush or a couple of marked fruit are all within the normal range and need nothing done about them. Reaching for a spray in response to those does more harm than the problem, particularly around a tree that flowers for bees.
There is one real exception, and it is serious enough to justify the rest of this page. Chinese quince belongs to the rose family, which is the family that fireblight moves through, and it is fully susceptible.
| Problem | First sign | When it appears | What to do |
|---|---|---|---|
| Fireblight | Wilted shoot tip hooked over, leaves blackened and clinging | Warm wet weather at and after flowering | Cut 18 in (45 cm) into clean wood, sterilize the blade each cut |
| Brown rot | Soft brown patch on the fruit with rings of buff pustules | Late summer into autumn | Remove every affected fruit from tree and ground |
| Bruise rot in store | Browning under an impact mark | After picking | Handle one fruit at a time; process marked fruit at once |
| Leaf spot | Scattered small dark spots, some yellowing | Wet summers | Rake and remove fallen leaves; usually needs nothing more |
| Aphids | Curled soft tips on the spring flush | Spring | Nothing. Predators clear them. Stop feeding nitrogen |
| Scale insects | Small brown bumps on twigs, sooty mold below | Any time, mostly on shaded crowded wood | Thin the canopy in winter; scrub twigs only, never the trunk |
| Sunscald or frost crack on the trunk | Split or dead strip of bark | Late winter | Shade the stem with planting; do not wrap or paint the trunk |
Fireblight, the one that can kill the tree
Fireblight is a bacterial disease of the rose family, and it is the only problem on this tree worth being genuinely vigilant about. The first sign is sudden and unmistakable once you have seen it: a shoot tip wilts within a day or two, bends over into a shepherd's crook, and the leaves turn black or dark brown and hang on the branch instead of falling, as if they had been scorched. Sometimes a milky ooze appears on the affected wood in humid weather.
It enters through open flowers in warm wet weather and through any fresh wound, which is why pruning in the wet and pushing the tree with nitrogen both raise the risk substantially. Soft, sappy, fast-grown shoots are the easiest tissue for it to move through. From the shoot it works steadily downward, and if it reaches a main limb or the trunk the tree is finished, which on a species grown for its trunk is the whole loss.
There is no home spray that cures it. The only treatment is surgery, done the day you see it rather than at the next convenient weekend. Cut the affected branch at least eighteen inches (45 cm) below the lowest visible blackening, into clearly healthy wood, and take the prunings out of the garden or burn them. Disinfect the blade with alcohol or household disinfectant between every single cut, because the tool carries the bacteria straight into the next wound. If blackening has reached the main trunk, take the tree out rather than leave a reservoir next to your apples, pears and any hawthorn in the hedge.
- Walk the tree weekly after flowering In warm humid spells, look along the shoot tips once a week. Fireblight caught on one shoot costs a branch; fireblight caught a month later costs the tree.
- Cut far below the damage Measure eighteen inches (45 cm) down from the lowest discoloration and cut there, into wood that is clean and green when you nick the bark. Bacteria run ahead of the visible symptoms.
- Sterilize between every cut Wipe or dip the blade in alcohol or household disinfectant after each cut, including cuts on the same branch. Skipping this is the commonest way people spread it around their own tree.
- Remove the prunings from the garden Burn or bin them. Do not chip them for mulch, leave them in a pile behind the shed, or add them to an open potting mix heap near other rose family plants.
- Stop feeding and stop wet pruning Cut out nitrogen for the rest of the season and never prune in wet weather again. Both reduce the amount of soft tissue and open wet wounds available to the bacteria.
Fruit rots, which start as handling damage
The other problem you will actually meet is rot in the fruit, and on this species it is nearly always a consequence of impact rather than of disease pressure. The fruit is heavy, and a drop onto paving, a knock against a branch in wind or a careless tip from crate to crate breaks the skin or crushes the flesh beneath it. Brown rot enters at that point, spreads as a soft brown patch, often with buff pustules in rings, and the fruit either falls or dries into a hard black mummy that hangs on the branch through winter.
Those mummies and any rotten fruit left on the ground are the source of next year's infection, so pick them off and remove them at the same time as the autumn leaf clearance. It costs nothing extra and is the most effective single thing you can do about rot without spraying.
The rest of the answer is at the picking stage rather than in the garden. Thin the crop so fruit does not hang in contact with a branch or with another fruit, pick before the tree drops anything, take the whole weight in your hand as you twist, and lay each fruit down individually rather than dropping it into a bucket. Fruit handled that way keeps for weeks; fruit tipped from container to container rots within days.
Minor troubles, and when to do nothing at all
Aphids curl the soft tips of the spring flush and look far worse than they are. On an established tree the predators clear them within a few weeks and no action is needed at all. Persistent heavy aphid populations are a message about feeding rather than about aphids: the tree is making too much soft growth and should not be fed.
Scale insects show as small brown bumps along twigs, usually in the shaded crowded parts of the head, with sticky honeydew and black sooty mold on the leaves below. The cure is light and air, achieved by thinning whole branches in winter, not by treating the insects. Never take a brush or a scraper to the trunk to deal with scale or with lichen; the bark is the reason you grew the tree and it will not recover from being scrubbed.
Leaf spotting in a wet summer, a little early leaf fall, moss and lichen on old bark and a few marked fruit are all cosmetic. Rake up and remove fallen leaves in autumn as a matter of routine, keep the center of the tree open so air moves through it, and beyond that let the tree be. Doing nothing is very often the correct treatment on this species.
Keep a short note each year of the date any fireblight appeared, which branch it was on and how far back you cut, plus how many fruit were rotten at picking. Fireblight risk tracks warm wet weather at flowering, and two or three years of notes will tell you whether you are in a bad location for it or simply had one bad season.