What is Dutch Elm Disease?

Pests and Diseases Toolbox Talk

25th March 2020 | Info

Common Name: Dutch Elm Disease/Vascular Wilt 

Scientific Name: Ophiostoma novo-ulmi 

Affects: Elm species, especially those in the UK 

Dutch Elm Disease (DED) is a severe tree disease that has killed millions of elm-tree species since first coming to the UK in the 1960s.  

What is it?

The disease is caused by the fungus Ophiostoma novo-ulmi which is spread by Elm Bark Beetles (Scolytus scolytus). Elm bark beetles naturally breed in the bark of dead, diseased, recently cut or weaker elm trees (typically those above 20 years old). They then move on to more healthy trees to feed, which is how the disease then proceeds to spread. Spores are then released and enter the tree through its xylem, releasing toxins and blocking vessels. The blocking of vessels is then what causes the tree to die.  

How is it Spread?

DED is spread easily due to Elm bark beetles which feed on healthy trees, but also due to the movement of elm products such as logs or mulched bark.  

The Symptoms/What You Should Look Out For

Typically, Dutch Elm Disease is more prevalent between the summer and autumn months, making them a key time of year to keep a lookout for any symptoms your trees may be showing. 

You should look out for: 

  • Clusters of yellow leaves that form in summer and wilt and fall very quickly 
  • Shoots that die back from the tip 
  • Twigs that bend down in a hook-like shape
  • Darks streaks underneath the bark of twigs or dark spots/rings in the crosssection of twigs 

[Bark of a diseased Elm]


It important that we take actions towards preventing further widespread of the disease. Here are some methods that have been suggested: 

  • Not planting native Elms which are more susceptible to the disease. (RHS) 
  • Carrying out sanitary felling of dead or dying elms to remove the Elm Bark Beetles habitat which in turn helps to slow down the spread of the disease. (Woodland Trust)
  • Replant in place of dead elms plants that have been propagated from trees that have a proven resistance. (Woodland Trust) 

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