Coral spot, so-called because after affected branches die, they develop pinhead-sized coral-pink fungal pustules. It is a disease caused by the fungus Nectria cinnabarina, causing die-back of branches of woody plants, but the causal fungus is a weak pathogen and its presence often indicates that the plant has other problems.

Among broadleaf trees and shrubs, Acer, Aesculus (horse chestnut), Carpinus (hornbeam), Fagus (beech), Juglans (walnut) and Tilia (lime) are among the more susceptible to attack. It is rarely found on conifers.

The small coral-pink fungal pustules may be seen at any time of year.

Symptoms:

• Die-back of branches, often those that have been broken or pruned further up.
• After death, pinhead-sized pink pustules of the causal fungus appear on the bark.
• There are no chemical or non-chemical controls available.
• Always prune in dry weather. When carrying out routine pruning, cut branches through the collar (ring of slight swelling found at the base of branches). Healing of wounds occurs most quickly here, compared to leaving stubs (snags) or cutting flush with the bough or trunk. If die-back occurs after pruning, remove dead material to avoid further infection.
• Prune out infections promptly and cut back to healthy wood. Do not leave dead wood to moulder and generate spores in damp corners of the garden.
• If a plant is attacked repeatedly, check for other stress factors that could be weakening it and alleviate these if possible.