Why Are My Cherry Tree Leaves Curling?

Curled or distorted cherry leaves look alarming, but they usually point to one of just a handful of causes. Catching it early matters because curled leaves signal that the tree is under stress — whether from insects feeding on sap, a virus, drought or a fungal problem — and a stressed tree is less able to fill out a good fruit crop. Examine the underside of leaves first: that is where most of the evidence hides.

Black cherry aphid — the most common cause

The black cherry aphid (Myzus cerasi) is the most frequent culprit. Colonies of dark, almost black aphids cluster on the underside of young leaves in spring, causing them to curl tightly downward and inward. The curled leaves provide the colony with shelter, making contact sprays less effective once curling has occurred. Look for sticky honeydew and sooty mould on surfaces below the affected shoots. Encourage natural predators — ladybirds, lacewings, parasitic wasps — and in severe cases spray with an insecticidal soap or neem oil solution before curling tightens, coating the undersides thoroughly.

Drought and heat stress

Cherry trees roll their leaves upward and inward as a moisture-conservation response during hot, dry spells. This physiological curling is temporary — the leaves flatten again once the soil is adequately moist. If you see uniform upward rolling across the whole canopy during a dry period, with no insects present and no sticky residue, water stress is the explanation. Deep watering at the root zone (slowly, to penetrate to 30–40 cm depth) and a thick mulch of organic matter extending to the drip line will reduce the problem in subsequent dry periods.

Powdery mildew

Young shoot tips and the newest leaves are most susceptible to powdery mildew infection. The fungus causes a fine white or grey powder on the upper leaf surface and often causes young leaves to cup or twist. Remove and bin affected shoot tips — do not compost them — and ensure good air circulation through the canopy by thinning crossing branches during winter pruning. Avoid high-nitrogen feeding in late summer, which promotes soft, susceptible growth.

Cherry leaf roll virus

This virus causes a rolling and distortion of leaves, sometimes with yellow mottling. It is spread by nematodes in the soil and through infected planting material. There is no chemical cure. If the tree is young and severely affected, replacement on a clean site with certified disease-free stock is the only reliable solution. Mature trees with mild symptoms can often crop adequately for many years.

Wind damage

Cherry trees in exposed positions can develop a chronic leaf-curl from desiccating winds even when soil moisture is adequate. Windbreak planting on the prevailing side, or training against a sheltered wall, removes the problem for newly planted trees. Established trees in very exposed positions benefit from a deep mulch and regular watering during dry windy spells.