Ash Dieback

Symptoms by part

Causes

• The fungus spreads primarily through airborne spores released from fallen leaves during the growing season.
• High humidity and damp conditions favor the development and spread of the fungal spores.

Could be confused with

• Honey Fungus · Honey fungus typically shows white fungal mats under the bark at the base of the tree and produces mushrooms at the trunk base, whereas Ash Dieback lesions are usually higher up on branches.
• Phytophthora root rot · This causes general yellowing and thinning of the canopy without the specific diamond shaped lesions on the stems characteristic of Ash Dieback.

Treatment

1. Prune out infected branches that show visible lesions, ensuring you cut well back into healthy wood to remove the fungus.
2. Collect and destroy all fallen leaves from beneath the tree in autumn to reduce the source of spores for the following year.
3. Remove and dispose of severely infected trees that pose a safety hazard to prevent further spread.

Without chemicals

• Pruning infected branches.
• Clearing and burning or deep burying fallen leaf litter.
• Selecting resistant ash varieties if replanting.

Preventing it

• Avoid planting new ash trees in areas where the disease is already prevalent.
• Ensure good airflow around trees by avoiding overcrowding.
• Clean pruning tools thoroughly with a disinfectant after working on an infected tree to prevent spreading spores to healthy plants.

When to act

Act as soon as you notice lesions or crown thinning to manage the spread. If a tree shows significant canopy loss or structural damage, consult a professional tree surgeon to assess safety and removal needs.

Questions people ask

Can my ash tree recover from Ash Dieback?

While some trees show a degree of tolerance, most infected trees will continue to decline over several years and eventually die.

Is there a chemical spray to cure Ash Dieback?

No, there are no chemical treatments available to cure this fungal disease.

Do I need to remove my tree immediately?

Not necessarily, but you should have a tree surgeon assess the tree for safety if it is near buildings, roads, or public areas, as dead branches can become brittle and fall.

Plants it affects

• European Ash