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Hazelnut Blight

Disease

Hazelnut Blight is a fungal disease that causes sunken lesions and cankers on the branches of hazelnut trees. It is a serious concern because it can girdle stems and eventually kill entire branches or the whole tree if left untreated.

Symptoms by part

Stems

You will see small, sunken, dark spots or cankers that eventually expand to girdle the branch, causing the leaves above the infection to wilt and die.

Causes

  • High humidity and frequent rainfall that keeps the bark wet for extended periods.
  • Wounds on the branches caused by pruning, insects, or storm damage that allow the fungus to enter.
  • Poor air circulation within the tree canopy which prevents the bark from drying out.

Could be confused with

  • Winter injury · Winter damage usually appears as uniform browning or splitting on the sunny side of the tree rather than localized, sunken cankers.
  • Bacterial blight · Bacterial blight often causes more spotting on the leaves and buds, whereas fungal blight is primarily focused on stem cankers.

Treatment

  1. Prune out any branches showing visible cankers as soon as you spot them.
  2. Make your cuts at least 6 to 12 inches below the visible edge of the canker into healthy, clean wood.
  3. Sterilize your pruning shears with a solution of rubbing alcohol between every single cut to avoid moving the fungus to healthy parts of the tree.
  4. Collect and burn or bury all pruned material immediately to prevent spores from spreading.

Without chemicals

  • Prune the tree canopy to improve airflow and sunlight penetration.
  • Remove and destroy all infected plant debris from the ground beneath the tree.
  • Avoid overhead watering that keeps the stems wet.

Chemical options

  • Tebuconazole, apply as a foliar spray to protect healthy stems during wet weather, follow the label.
  • Triticonazole, apply as a protective spray on stems, follow the label.

Preventing it

  • Select and plant resistant hazelnut varieties whenever possible.
  • Keep the area around the base of the tree clear of fallen leaves and debris.
  • Prune trees during dry weather to ensure wounds heal quickly.
  • Space trees properly to encourage good air movement.

Season

The warm growing season, especially during periods of wet weather.

Spread risk

High

Severity

High

When to act

Act immediately upon seeing the first signs of sunken cankers to save the branch. If the main trunk becomes heavily cankered, it is best to remove the entire tree.

Think it's Hazelnut Blight?

This guide covers the general picture. Pocket Botanist looks at your actual plant from a photo and tells you what's really going on, how serious it is, and what to try first. Identification and a health check are free.

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Questions people ask

Can I compost the infected branches?
No, you should burn or dispose of infected material in the trash to ensure the fungus does not survive and spread back to your trees.
Will the tree recover on its own?
Hazelnut Blight is aggressive and rarely goes away without intervention, so active pruning is necessary to stop the spread.

Plants it affects

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This guide was generated with AI and is general information, not horticultural advice. Read about how we build these guides.