Plant problems

Why Are My Quince Leaves Curling?

Q: How do I treat quince leaf blight?

Quince leaf blight (Entomosporium mespili) is a fungal disease that overwinters on fallen leaves and on infected twigs and buds. The primary control is hygiene: collect and destroy all fallen leaves in autumn and winter rather than composting them (the spores survive composting). Prune out infected twigs in winter, cutting back to healthy wood, and dispose of prunings. In spring, as the buds are opening, apply a copper-based fungicide spray and repeat every 10 to 14 days through the wet spring and early summer period when infection risk is highest. Improve air circulation around the tree by removing crossing branches and keeping the centre of the tree open. Avoid overhead watering, which keeps the foliage wet and favours spore germination. Resistant varieties are not widely available, but some quince cultivars show less susceptibility than others; 'Leskovac' and 'Vranja' are commonly grown in the UK and both can suffer significant blight in wet years.

Q: When does quince fruit ripen in the UK?

Quince (Cydonia oblonga) fruit in the UK ripens from October to November; it cannot be eaten raw (unlike most fruit) as it is extremely hard, astringent, and tart when uncooked, but it transforms when cooked into a fragrant, deep pink or orange preserve. Quince makes outstanding jams, jellies, and the Spanish confection membrillo (quince paste). The fruit should be harvested before the first hard frosts and stored in a cool, dry, dark place, where it will keep for several weeks; the characteristic powerful quince fragrance intensifies in store. Quince is one of the most fragrant of all tree fruits and a bowlful of ripe quinces perfumes a room. The fruit is fully ripe when it has turned from green to golden-yellow; under-ripe quince is harder and more tart. In the north of England and Scotland, quince fruit may not fully ripen outdoors in cool summers; wall-training against a south-facing wall helps in marginal areas.

Quince (Cydonia oblonga) is one of the oldest cultivated fruit trees, grown in UK gardens for centuries for its spectacular spring blossom, golden autumn fruit, and extraordinary fragrance. It is a tough, largely self-sufficient tree that asks for little, but it is susceptible to one significant disease in UK conditions: quince leaf blight, which can strip a tree of its leaves by midsummer in a wet year. Here is what causes quince leaf curling and what to do about it.

Quince leaf blight

Quince leaf blight (Entomosporium mespili, syn. Diplocarpon mespili) is the most common and serious disease of quince in the UK. It causes small, angular, reddish-brown spots on the upper leaf surface in spring and early summer; the spots enlarge rapidly in wet conditions, merge, and turn the whole leaf brown. Affected leaves curl and drop prematurely; a heavily infected tree can be completely defoliated by July or August. The disease overwinters on fallen leaves and infected stem tissue, and the spores are spread by rain splash in spring. Repeated severe infections weaken the tree progressively and reduce fruit yield.

What to do

Collect and destroy all fallen leaves in autumn rather than composting them. Prune out infected twigs in winter, cutting back to healthy wood. Apply a copper-based fungicide spray as buds open in spring and repeat every 10 to 14 days through the wet spring period. Improve air circulation by keeping the centre of the tree open. Avoid wetting the foliage when watering.

Aphids

Several aphid species attack quince in spring, including the rosy apple aphid (Dysaphis plantaginea) and the apple-grass aphid (Rhopalosiphum insertum). They colonise the young shoots and newly opening leaves, causing the leaves to curl under and crumple as they develop. The shoot tips may bunch and distort; the aphids are typically pink, greenish, or grey in colour and covered in a waxy bloom. Aphids on quince are at their worst in late April and May as the new growth expands; populations typically reduce naturally as predators build up through summer.

What to do

Pinch off and destroy the most heavily infested shoot tips. Apply insecticidal soap or pyrethrin spray to the affected growth. Encourage natural predators by planting companion flowers. Already-curled leaves will not straighten; the tree will produce new, healthy growth once the aphid population is controlled. A winter wash of tar oil applied to dormant branches can reduce overwintering aphid eggs.

Fire blight

Fire blight (Erwinia amylovora) causes the shoot tips of quince to collapse and turn brown suddenly in late spring and early summer, as if they have been scorched by fire. The leaves on affected shoots curl, turn brown, and remain attached to the dead stem. A characteristic shepherd's crook bending of the shoot tip is often visible. Fire blight enters through open flowers and is spread rapidly in warm, wet spring conditions. It can spread down from the shoot tip into the main branches. There is no chemical cure.

What to do

Remove infected material by cutting back at least 30 cm below the visible margin of the browning, into healthy white wood. Sterilise cutting tools between each cut with a disinfectant (methylated spirits or a bleach solution). Dispose of all infected material; do not compost it. Avoid high-nitrogen fertilising, which promotes the soft, vulnerable growth that fire blight colonises most readily. Severely infected trees may need to be removed.

Powdery mildew

Powdery mildew (Podosphaera clandestina and related species) affects quince in dry summers, appearing as a white, powdery coating on the young leaves and shoot tips. Affected leaves curl and distort. Mildew on quince is less damaging than leaf blight and is more of a problem in dry spells than wet ones (unlike leaf blight, which thrives in wet weather). Container-grown quince and those in sheltered courtyard positions where air circulation is limited are more susceptible.

What to do

Remove infected shoots and dispose of them. Apply a potassium bicarbonate or sulphur-based fungicide at the first sign of infection. Ensure consistent moisture at the roots; drought-stressed trees are significantly more susceptible to powdery mildew. Improve air circulation around the tree.

Frequently asked questions

Why are my quince leaves curling?

Quince (Cydonia oblonga) leaves curl and brown most commonly because of quince leaf blight (Entomosporium mespili), aphid infestation, or fire blight (Erwinia amylovora). Quince leaf blight is the most common disease, causing angular, reddish-brown spots that enlarge and merge; affected leaves turn brown, curl, and drop prematurely in summer. Severe blight can defoliate the tree entirely by midsummer. Aphids colonise the young shoots in spring, causing the leaves to curl under and crumple as they develop. Fire blight causes the shoot tips to collapse suddenly and turn brown, as if scorched, with leaves curling and remaining attached to the dead stem.

How do I treat quince leaf blight?

Quince leaf blight (Entomosporium mespili) control relies primarily on hygiene: collect and destroy all fallen leaves in autumn and winter rather than composting them. Prune out infected twigs in winter, cutting back to healthy wood. In spring, as the buds are opening, apply a copper-based fungicide spray and repeat every 10 to 14 days through the wet spring and early summer period. Improve air circulation by removing crossing branches and keeping the centre of the tree open. Avoid overhead watering, which keeps the foliage wet and favours spore germination.

What is fire blight and does it affect quince?

Fire blight is a serious bacterial disease caused by Erwinia amylovora that affects members of the rose family including quince, apple, pear, and medlar. Affected shoot tips turn brown and wilt suddenly, as if scorched, with leaves curling and remaining attached to the dead stem. The infection typically enters through the flowers in spring. There is no chemical cure; the only treatment is to remove infected material by cutting back at least 30 cm below the visible margin of the infection, sterilising the cutting tool between cuts. Severely infected trees may need to be removed.

When does quince fruit ripen in the UK?

Quince fruit in the UK ripens from October to November. It cannot be eaten raw as it is extremely hard, astringent, and tart when uncooked, but transforms when cooked into a fragrant, deep pink preserve. Quince makes outstanding jams, jellies, and membrillo (quince paste). Harvest before the first hard frosts and store in a cool, dry, dark place for several weeks. The fruit is ripe when it has turned from green to golden-yellow. In the north of England and Scotland, quince fruit may not fully ripen outdoors in cool summers; wall-training against a south-facing wall helps in marginal areas.