If your citrus leaves are curling up, it’s usually a sign that something is stressing the tree. In New Zealand gardens, the most common causes are fungal disease, pests, or environmental stress such as wind, heat or irregular watering.

Citrus scab (verrucosis)

If the curled leaves are also thickened, distorted and marked with rough, scabby patches, your tree may be affected by citrus scab (verrucosis). This fungal disease is more common in warm, humid areas and spreads during wet conditions. It affects new growth, causing leaves to curl and become misshapen.

Prevention is the key to managing citrus scab. Once leaves are badly affected, they won’t return to normal, so the focus is on protecting healthy new growth.

• Remove and dispose of badly infected leaves where practical.
• Apply a copper-based spray such as copper oxychloride as a preventative during active growth periods, following label directions carefully. Copper works by protecting new leaves before infection occurs.
• Keep the tree well fed with Daltons Premium Citrus & Fruit Tree Fertiliser to encourage strong, healthy growth that can better cope with disease pressure.
• Ensure good airflow around the tree by lightly pruning if it is very dense.

Other causes

If you don’t see scabby marks and the curling is mainly on soft new growth, check for pests such as aphids or leafminer. In windy or very hot conditions, leaves can also curl as a protective response, especially if the soil is drying out too quickly.

If you’re unsure what’s causing the curling, take a close look at the newest growth first - it usually tells the story.

For more advice read our guides on growing citrus.