Why Are My Lychee Leaves Curling?

Lychee erinose mite

Lychee erinose mite (Aceria litchii) is a microscopic eriophyid mite, invisible to the naked eye, that burrows into the epidermis of young developing lychee leaves. The mite triggers the leaf to produce an abnormal growth of elongated, matted hairs (the erineum) on the lower leaf surface; these hairs are cream or pale brown when new, darkening to rust or dark brown as they age and the mites colonise them. The infected leaf puckers and curls strongly around the affected areas; heavily infested leaves may be grotesquely distorted and useless for photosynthesis. The rust-coloured felt patches on the leaf underside are highly distinctive and unlike any other lychee problem.

What to do

• Remove and destroy all badly affected leaves to reduce the mite population. Treat remaining foliage with a sulphur-based or wettable sulphur fungicide spray, which is effective against eriophyid mites; apply to both leaf surfaces, particularly the undersides. Repeat at 10 to 14 day intervals. In the UK, erinose mite is not established outdoors; indoor infestations are usually introduced on new planting material. Quarantine new lychee plants for several weeks before placing near existing trees.

Low humidity

Lychee originates from the humid subtropical climate of southern China and northern Vietnam, where humidity is typically 70 to 80% year-round. In UK homes and conservatories, particularly in winter when central heating is running, humidity often drops to 30 to 40%, causing the leaf margins and tips to brown, dry, and curl. Low humidity does not cause the dramatic distortion of erinose mite but produces a gradual, consistent browning that progresses from the leaf tips inward.

What to do

• Place the pot on a wide gravel tray filled with water (the pot above the water level on the gravel, not sitting in water). Mist the leaves with rainwater or distilled water in the mornings. Group with other plants to raise local humidity. Keep away from radiators and heat vents. In a heated greenhouse, damp down the floor and staging in the morning to raise humidity throughout the day.

Cold damage

Lychee is a subtropical tree adapted to mild winters with occasional cool temperatures. It tolerates brief, light frosts (to about -2°C) in sheltered conditions but is damaged by prolonged cold below 5°C. Cold stress in UK conditions causes the leaves to yellow (particularly the older, lower leaves), curl at the margins, and drop. New growth produced in cool conditions is often pale and weak. Lychee actually benefits from a cool (but frost-free) winter rest at 5 to 12°C to initiate flower bud formation; this is distinct from cold damage, which occurs below 5°C.

What to do

• Protect lychee from temperatures below 5°C at all times. A cool winter rest at 5 to 12°C for 6 to 8 weeks is beneficial for flower induction but must not drop into damaging cold. Reduce watering during the cool period. Move the plant to a warmer position in late February to stimulate new growth for spring.

Red spider mite

Red spider mite (Tetranychus urticae) can also colonise lychee grown in warm, dry greenhouse or conservatory conditions, causing pale stippling and bronzing of the leaves, fine webbing on the undersides, and eventual leaf curl and drop. Spider mite on lychee is less common than erinose mite but can occur when conditions are very dry and warm. It is visually distinct from erinose mite damage: spider mite produces a general pale stippling across the whole leaf, while erinose mite produces discrete felt-like brown patches primarily on the leaf underside.

What to do

• Increase humidity. Introduce Phytoseiulus persimilis predatory mites for biological control. Remove heavily infested leaves. Treat with insecticidal soap or a plant-safe miticide spray if the infestation is severe before biological controls are established.

Frequently asked questions

Why are my lychee leaves curling?

Lychee (Litchi chinensis) leaves curl most commonly because of lychee erinose mite (Aceria litchii), low humidity, or cold temperatures in UK indoor conditions. The lychee erinose mite is a microscopic eriophyid mite (too small to see with the naked eye) that burrows into the underside of young lychee leaves and causes an abnormal growth of hairs (erineum) on the leaf surface; the infected leaves blister, pucker, and curl strongly as the tissue is distorted by the mite's feeding, and a brown, rust-coloured felt-like patch of abnormal hairs appears on the underside. Low humidity in UK homes and greenhouses causes the leaf margins and tips of lychee to curl and brown; lychee is a subtropical plant from southern China that requires higher humidity than most UK interiors provide. Cold temperatures below 5°C cause lychee leaves to yellow and curl as the subtropically-adapted plant enters cold stress.

Can I grow lychee in the UK?

Lychee (Litchi chinensis) can be grown in the UK as a container plant in a heated greenhouse or large conservatory, or as a houseplant in a warm, bright position, but producing fruit in UK conditions is very challenging. Lychee requires a cool (but frost-free) winter rest period of 6 to 8 weeks at 5 to 12°C to initiate flower bud formation; without this dormancy period the tree will grow vegetatively but not flower. After the cool period, it needs high heat and light in spring and summer to develop flowers and fruit. In a well-managed heated greenhouse in the UK, lychee can be induced to flower and fruit, but the process requires careful temperature management. Lychee can be grown from the seed of a fresh fruit, though seed-grown trees take 7 to 12 years to produce fruit and may not come true to the parent variety; air-layered or grafted trees from specialist nurseries fruit much sooner. Lychee tolerates brief light frosts (down to about -2°C) but is damaged by prolonged cold below 5°C.

What is lychee erinose mite?

Lychee erinose mite (Aceria litchii, formerly Eriophyes litchii) is a microscopic eriophyid mite that is the most significant pest of lychee trees worldwide. It is far too small to see with the naked eye (under 0.2 mm long) but its effects on the leaves are highly distinctive. The mites burrow into the epidermis of young developing leaves and trigger the leaf to produce an abnormal growth of elongated, matted hairs (erineum); these hairs are cream-coloured when new and turn rust-brown to dark brown as the mites colonise them. The affected leaf surface is covered in these felt-like patches, and the leaf blade curls and puckers strongly around the infected areas. Heavily infested leaves may be so distorted that they cannot function normally. Lychee erinose mite can be inadvertently introduced on imported lychee planting material; quarantine new plants before introducing them near existing lychee trees.

How do I increase humidity for my lychee plant?

Lychee prefers humidity of 60 to 80%; most UK homes and conservatories have humidity of 30 to 50% in winter, which causes leaf tip browning and curling. The most effective methods for increasing humidity around a lychee plant are: placing the pot on a wide gravel tray filled with water (the pot sits above the water level on the gravel, not in it, so the roots are not waterlogged); grouping lychee together with other moisture-loving plants so their collective transpiration raises the humidity of the surrounding air; misting the leaves with rainwater or distilled water in the morning so the water evaporates during the day rather than sitting on the leaves overnight; or using a room humidifier placed near the plant. Avoid placing lychee near radiators or heat vents, which dry the air significantly. In a greenhouse, damping down (wetting the floor and staging) in the morning is the traditional method of raising humidity.