Coral Spot on Hazelnut: Orange Pustules on Dead Branches

Noticing small, vivid orange or salmon-pink raised pustules scattered across the bark of dead or dying hazelnut branches? This is coral spot, caused by the fungus Nectria cinnabarina. It is a very common sight in UK gardens on a wide range of woody plants, and hazelnut is frequently affected. Understanding its role as a secondary invader rather than an aggressive pathogen is the key to responding appropriately.

What Is Coral Spot?

Nectria cinnabarina is a wound parasite and saprotrophic fungus — it primarily colonises dead or already-dying wood rather than infecting healthy living tissue directly. The bright coral or salmon-pink pustules (which are the fungal spore-producing bodies called sporodochia) appear on the bark of branches that have died for another reason: frost damage, drought stress, poor pruning cuts that left stubs, physical injury, or any other cause of dieback. On occasion, the fungus can spread into adjacent living tissue from a dead stub, causing further dieback in a tree that is already stressed.

Why It Appears on Hazelnut

Hazelnut naturally produces a lot of sucker and water-shoot growth, some of which dies back each year. Pruning cuts that are not made cleanly to a node or junction leave stubs that die and provide ideal entry points for coral spot. Branches that have been weakened by big bud mite, drought, or mechanical damage are also commonly colonised. The fungus is widespread in garden environments and its spores are airborne year-round, so any dead wood is quickly found.

Management

The treatment for coral spot on hazelnut is straightforward: remove all dead and affected wood. Cut back infected branches to healthy wood — where the cut surface shows clean white tissue without brown staining. Make cuts at a clean angle just above a healthy bud or junction, leaving no stubs. Disinfect cutting tools between cuts using methylated spirits or a dilute bleach solution. Dispose of all removed material in the bin or by burning — do not compost it, as the spores remain viable.

Preventing Recurrence

Coral spot on hazelnut is almost always a symptom of management issues rather than a primary disease problem. Preventing it means eliminating the dead wood that feeds it: prune cleanly at the right time of year (late summer to early autumn), remove suckers and water shoots before they die back, and maintain overall plant vigour through good feeding and mulching. A healthy, vigorously growing hazelnut with well-made pruning cuts and no unnecessary stubs rarely suffers from significant coral spot.

When to Be Concerned

Alarm is warranted if coral spot appears on green, apparently healthy branches or if dieback is spreading from a coral spot lesion into the main framework of the plant. This indicates either that the plant is significantly stressed or that the fungus is showing more aggressive behaviour. In this case, check for other stressors — waterlogging, compacted soil, root damage — and address them in addition to removing the affected wood.