Quick facts

Common name: Dutch elm disease

Scientific name: Ophiostoma novo-ulmi

What does it affect?: elm species (tree in the genus Ulmus)

Areas affected so far: throughout the UK except for the far north

Origin: thought to be Asia

What does Dutch elm disease look like?

Symptoms include:

  • Clusters of yellow leaves that wilt and fall.
  • Shoots that die back from the tip.
  • Twigs that bend down in a ‘shepherd’s crook’.
  • Dark streaks underneath the bark of twigs, or dark spots and rings in the cross-section.

What is Dutch elm disease?

Dutch elm disease is caused by the fungus Ophiostoma novo-ulmi which is spread by the elm bark beetle. It got its name from the team of Dutch pathologists who carried out research on the diseases in the 1920s.

Elm tree dying of Dutch elm disease

Credit: Winston Fraser / Alamy Stock Photo

What happens to the tree?

Elm bark beetles breed in the bark of cut, diseased or otherwise weakened elm trees then disperse to healthy elm trees where they feed. As they feed, the spores of O. novo-ulmi are introduced into the xylem (channels for water and nutrients) of the healthy tree, releasing toxins and causing the vessels to block and the tree to wilt and die.

Where has Dutch elm disease impacted?

Since its introduction to the UK, it has killed millions of our elm trees. It has devastated populations in mainland Europe and North America too.

How did Dutch elm disease get here?

Dutch elm disease was accidentally imported into the UK from Canada in the late 1960s. It spread quickly, reaching Scotland in just 10 years.

The movement of elm products caused the spread of the disease, particularly on logs with bark attached but also through saplings, crates and mulching bark.

Outlook

There has been work in universities across the world to develop resistant elms and these hybrids are subjected to inoculum trials to assess their resistance to Dutch elm disease.

While these resistant strains look similar to English varieties of elm, it’s important to realise that they are exotic species. They might not perform the same ecosystem function so replacing elms with them is not a complete solution.

The spread of the disease can also be slowed with sanitary felling of dead and dying trees which removes the habitat of the beetles which carry the fungus. This type of management has been very successful in East Sussex where there are now more elms than there were before the disease hit. Some elms have been replaced with plants propagated from trees that have resisted the disease so far.

What are we doing about it?

To the spread of pests and diseases like Dutch elm disease we have:

  • Developed a UK and Ireland 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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