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Quick facts

Common name: none

Scientific name: Sirococcus tsugae

What does it affect?: Atlas cedar, deodar cedar, cedar of Lebanon, western hemlock, eastern hemlock, mountain hemlock

Areas affected so far: across the UK

Origin: not known

What does Sirococcus tsugae damage look like?

Symptoms include:

  • Death of the shoot tips and branches of mature trees, usually changing the needle colour to brown or pink.
  • Cankers on the bark of shoots and branches which can cause dieback and death.
  • The dieback of side shoots can cause a curved ‘shepherd’s crook’ appearance.
  • Resin from the cankers with small fruiting bodies of the fungus on the needles and cankers themselves.
  • Death of seedlings.

What is Sirococcus tsugae?

Sirococcus tsugae is a fungal disease that causes shoot death and cankers on cedar and shoot death on hemlock. Scientists are still investigating the lifecycle of this fungus.

Where has Sirococcus tsugae impacted?

S. tsugae has been known in the US since 1966. In Europe, it was first reported in the UK and Germany in 2014. It is now found in a number of different locations across the UK.

How did Sirococcus tsugae get here and what impact will it have?

We don’t know how the first introductions happened. It most likely arrived via imported infected trees or possibly via infected imported seeds or cut foliage.

Biosecurity is very important with this type of pathogen. The disease is spread by spores from the needles and bark of the infected tree. Rain and wind spread the spores and they can also be transported on clothing, footwear and vehicle tyres.

What are we doing about it?

To combat pests and diseases like Sirococcus tsugae we have:

  • Developed a UK Sourced and Grown assurance scheme to make sure that all the trees we plant and sell are produced in the UK. 
  • Lobbied the Government to improve biosecurity at border points to stop new pests and diseases entering the UK.
  • Partnered with Observatree, a tree health Citizen Science project which trains volunteers to spot pests and diseases, thereby helping tree health authorities identify and manage outbreaks early.
Horse chestnut tree discoloured to yellow after a leaf miner infestation

Trees woods and wildlife

What we are doing about tree pests and diseases

We are fighting back against pests and diseases. Find out what we're doing to prevent the spread and protect the UK’s trees. 

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What to do if you spot Sirococcus tsugae

If you think you have seen the signs and symptoms of this disease, please report it to the plant health authorities via TreeAlert if you are in Britain, or TreeCheck if you are in Northern Ireland.

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