Why Are My Apple Leaves Curling?

Rosy apple aphid

Rosy apple aphid (Dysaphis plantaginea) is among the most economically significant apple pests in the UK and Europe. It overwinters as eggs on apple bark and hatches from the pink bud stage in April. The aphids are pink-grey to pink in colour and colonise the underside of young leaves, causing them to pucker, curl tightly, and often develop a distinctive reddish or purplish discolouration on the upper surface. Fruitlets on infested shoots remain small, distorted, and drop prematurely or produce deformed fruit at harvest. By midsummer the colonies migrate to plaintain weed (Plantago spp.) but the damage to the apple shoot is already done: the curled leaves and ruined fruitlets cannot recover.

What to do

• Inspect apple shoots carefully from the pink bud stage in April. This is the critical control window: colonies are visible but the leaves have not yet curled around them. Treat with insecticidal soap, pyrethrum, or an aphid-specific pesticide at this stage.
• Once leaves have curled tightly around the aphid colonies (typically by late April or May), contact insecticides cannot reach the insects inside. At this stage, remove and destroy the most heavily affected shoots if practical.
• Encourage natural predators: avoid broad-spectrum insecticides that kill ladybirds and hoverflies alongside the aphids. Growing flowering plants that attract beneficial insects near the apple tree provides long-term population control.
• In autumn, check the bark on shoots for the shiny, black overwintering eggs and spray with a winter wash (plant-based oil) to smother them and reduce the following year's infestation.

Apple leaf curling midge

Apple leaf curling midge (Dasineura mali) is a tiny fly whose larvae cause one of the most recognisable leaf symptoms on UK apple trees: the individual leaves roll upward from their margins into a narrow, tight, cigar-like cylinder. The rolling runs along the full length of the leaf. If a rolled leaf is carefully opened, tiny orange-white larvae (1 to 2 mm) are visible inside. There are up to five generations per year, with each successive generation continuing to roll new leaves through spring and summer. Young trees, nursery stock, and the soft growing tips of trained trees are the most severely affected.

What to do

• Pick off and destroy rolled leaves as they appear, removing the larvae inside. On a small, young tree this is practical and significantly reduces the population through the season.
• For severe infestations on young trees, an insecticide targeting the adult fly at the adult flight periods (April to May and again in June to August) reduces egg-laying and subsequent larval damage. Timing applications to coincide with adult emergence (when the first rolled leaves appear) is more effective than a fixed calendar spray.
• Established, mature apple trees tolerate apple leaf curling midge without significant effect on cropping. Control is most important on young trees in their first few years.

Powdery mildew

Apple powdery mildew (Podosphaera leucotricha) infects young growing tips in spring, producing a white, powdery coating that causes the young leaves to curl, narrow, and harden. Mildewed shoots at bud burst appear pale and stiff, with narrow, upward-curled, white-coated leaves. The mildew overwinters in infected buds and re-infects new growth each spring from these primary sources.

What to do

• Prune out mildewed shoot tips in spring as they appear: cut back to 15 to 20 centimetres below the visible mildew and destroy the removed material.
• Apply a fungicide (sulphur, myclobutanil, or potassium bicarbonate) from the green cluster stage every 10 to 14 days through spring to reduce secondary spread.
• For long-term control, choose mildew-resistant apple varieties when planting new trees: 'Fiesta', 'Discovery', 'Sunset', and 'Egremont Russet' are less susceptible than older varieties such as 'Cox' and 'Bramley'.

Woolly aphid

Woolly aphid (Eriosoma lanigerum) colonises apple bark rather than leaves, but heavy infestations affect the tree's overall vigour and may cause leaf curling and general decline. The aphid is easily recognised by the white, waxy, wool-like coating it produces on the bark of pruning wounds, cracks, and on the stems. It does not produce the leaf curling symptoms of rosy apple aphid and leaf curling midge but is worth noting when inspecting the tree for leaf problems.

What to do

• Scrub small woolly aphid colonies from the bark with a stiff brush. Insecticidal soap or methylated spirits applied to the colonies with a brush provides contact control. The parasitoid wasp Aphelinus mali is an effective natural enemy that provides useful biological control.

Frequently asked questions

Why are my apple leaves curling?

Apple leaves curl for two main reasons: rosy apple aphid (Dysaphis plantaginea) and apple leaf curling midge (Dasineura mali). Rosy apple aphid causes severe puckering, curling, and reddish or purplish discolouration of the leaves on infected shoots in spring; the aphids are visible as pink-grey colonies on the underside of curled leaves. Apple leaf curling midge causes a very different, very tight tube-like rolling of the leaf margins, where individual leaves roll up from the edges into a narrow cylinder; the tiny larvae are visible inside the rolled leaf when it is opened. Powdery mildew also causes the young growing tips to curl and distort with a white powdery coating. All three are common and identifiable by examining the nature of the curling and looking for the responsible pest or pathogen.

What is rosy apple aphid and how do I control it?

Rosy apple aphid (Dysaphis plantaginea) is one of the most damaging apple pests in UK gardens. It is a small, pinkish-grey to pink aphid that colonises apple leaves and fruit fruitlets in spring. Infested leaves curl tightly, pucker, and often develop a reddish or purplish discolouration. The affected shoots may become severely stunted and the fruitlets on infested shoots fail to develop properly, remaining small and distorted. The aphid migrates from apple to its summer host (plaintain weed, Plantago species) in midsummer, but the damage to the apple leaves and fruitlets has already occurred by then. Control: inspect apple shoots from the pink bud stage in April for the first colonies; treat with insecticidal soap or pyrethrum at this early stage before leaves have curled around the aphids. Once the leaves are curled, insecticides cannot penetrate to the aphids inside. Natural predators (ladybirds, hoverfly larvae, parasitoid wasps) provide useful longer-term control.

What is apple leaf curling midge?

Apple leaf curling midge (Dasineura mali) is a tiny fly whose larvae cause a very characteristic symptom: the leaf margins roll upward into a tight, narrow tube along the entire length of the leaf, like a tightly rolled paper tube. If you unroll the leaf, tiny, pale orange larvae (1 to 2 millimetres long) are visible inside. There can be several generations per year, and new growth is affected repeatedly through spring and summer. The midge is most damaging on young nursery trees and on the soft, growing new shoots of trained or espalier apple trees. Established trees with mature wood are less affected than young trees or newly planted whips. Control options include removing and destroying curled leaves (which removes the larvae inside), encouraging natural predators, and applying an appropriate insecticide targeting the adult fly in spring.

Why do my apple leaves have white powder on them?

White powder on apple leaves is apple powdery mildew (Podosphaera leucotricha). It infects the growing tips in spring, producing a white, felt-like coating on the young leaves, which causes them to curl, narrow, and harden. Affected shoots are sometimes described as 'silvered' in appearance. The mildew overwinters in infected buds and re-infects new growth each spring: buds that produce early, narrow, stiff, white-coated leaves in spring are carrying mildew infection from the previous season. Control: prune out mildewed shoot tips in spring as they appear; apply a fungicide registered for powdery mildew (sulphur, myclobutanil, or potassium bicarbonate) from the green cluster stage through to summer; improve airflow in the canopy by pruning to maintain an open centre; choose mildew-resistant varieties for future planting.