Sooty Bark Disease

Information for Arboricultural Contractors

PHOTO 2026 08 25 16 15 40[1]
PHOTO 2026 08 25 16 15 40[1]

Sooty Bark Disease

Information for Arboricultural Contractors

What is it?

Sooty Bark Disease (SBD) is a fungal disease that primarily affects sycamore (Acer pseudoplatanus). The fungus may remain latent within apparently healthy trees, with disease development and spore production associated with tree stress, prolonged drought and warm conditions – factors which are becoming more common in the UK. The disease can cause severe decline and may ultimately kill host trees.

Infected trees often contain billions of microscopic black spores. When these spores are disturbed and become airborne, such as during tree work, they present a significant occupational health hazard if inhaled.

Identification

Look for:

PHOTO 2026 08 25 16 14 52

Poor crown health, dieback or dead trees

PHOTO 2026 08 25 16 15 41[1]

Bark splitting, peeling or bulging

PHOTO 2026 08 25 16 15 41[3]

Dense black, soot-like spore masses on the main stem and branch framework

Trees affected by other issues may show similar symptoms. Poor crown health can have many causes, while dysfunction in the cambium may present as stem bleeding or staining, bark cracking or other similar signs. If SBD is suspected but identification is uncertain, seek advice from an arboricultural consultant or adopt the controls and PPE outlined here as a precaution. Samples may also be sent for laboratory analysis where required.

Why is is a health risk?

The spores are hyper-allergenic and may cause:

  • severe respiratory irritation
  • asthma-type symptoms
  • hypersensitivity pneumonitis

Symptoms may include:

Shortness of breath

Fever

Cough

Chills

Night sweats

Weight loss

Sooty Bark Disease spores are a substance hazardous to health.

Work involving infected trees should therefore be considered under the Control of Substances Hazardous to Health Regulations (COSHH).

Employers should:

  • dentify the hazard
  • assess the risk of exposure
  • implement suitable control measures
  • provide appropriate information, instruction and training
  • ensure suitable PPE is available and worn

A COSHH assessment should be completed and made available to operators. It should be supported by a site-specific risk assessment addressing hazards and control measures that may vary from site to site.

Identify the hazard before work begins.

Establish an appropriately sized exclusion zone to prevent exposure to third parties. This will often need to extend significantly beyond the exclusion zone normally required for tree work – potentially up to 50m – and should take account of wind direction.

Schedule work during or shortly after damp or wet weather where possible to minimise airborne spores. Material may also be manually wetted before processing (e.g. using a hosepipe or water bowser).

Minimise cutting, processing and handling. Where possible, retain material on site in as unprocessed a form as practicable (e.g. habitat piles).

Where processing is necessary, use mechanical means where available to reduce operator exposure.

During any work involving SBD, operators should wear:

  • FFP3 respirator – a half mask is normally appropriate and compatible with other PPE
  • Sealed safety goggles – worn beneath a mesh visor, or EN 166-rated eye protection may replace the visor where appropriate to the risk profile of the operation
  • Disposable hooded coveralls – worn over chainsaw PPE where required to minimise contamination
  • Task-specific PPE – all other PPE should remain appropriate to the task (e.g. chainsaw protective clothing)

Disposal

  • There are no specific statutory disposal requirements for Sooty Bark Disease in the UK. However, good practice is to:
  • Retain material on site wherever possible, e.g. minimally processed habitat piles, with controlled incineration or burial where practicable and legally permissible.
  • Transport material in a manner that minimises spore release where it cannot reasonably be avoided.
  • Do not retain infected timber for firewood or any other use where subsequent operator or third-party exposure is foreseeable.
  • Do not mix contaminated material with loads intended for reuse.
  • Confirm with third-party hauliers or receivers that they are able to accept contaminated material (e.g. biomass facilities).

Reporting

Forest Research encourages suspected cases to be reported through TreeAlert to help monitor the distribution of the disease within Great Britain. The Northern Ireland equivalent is DAERA’s TreeCheck.

Where SBD is known or suspected, this information should be communicated to everyone involved in planning, undertaking or commissioning the work.

Page image credits: Tom Hamments