Almost the whole of the Netherlands has been vaccinated against certain diseases, but now it is also trees’ turn. On Het Haagse Groen Merijn van Grieken writes about a special flu shot that 8.100 The Hague elms are administered.

A team of arborists will give the ‘flu shot’ to elm trees in the city from May. The vaccine should protect the trees against Dutch elm disease. Tree expert Paul explains why the jab is needed every year and Rosko explains in a video how the vaccination works. Spray it!


The elm is a tree that is common in The Hague. The city has approximately 20.000 elm trees that line streets and avenues. “This elm really belongs in our streetscape in The Hague. Elms like a poor soil and they can withstand the salty sea breeze,” says tree expert Paul Boeters of the Municipality of The Hague.

Just like people, trees can also get sick. “Elm disease is a kind of thrombosis,” explains Paul. A small animal is responsible for the highly contagious Dutch elm disease: the elm bark beetle. The animal transmits a fungal disease, which causes the deadly Dutch elm disease.


“The beetle is not aware of any harm and lays eggs behind the bark of a sick elm. They hatch in the spring and the beetles then drill holes in the bark. When it fledges, it takes the fungus with it to healthy trees. And so it can quickly spill over to healthy trees.”

Pricks around the trunk

To prevent disease, the elm trees in our city are given an annual jab. The injection should be done early in the growing season, when the elms are just emerging. The weather must also be nice. The bark must be dry, so that the tree absorbs the substance as it were.

About half of all elms get pricks around the trunk, the other half consists of largely newer elm species that are naturally better protected against Dutch elm disease. “The Hague was 000 years ago the first city with a vaccine against Dutch elm disease. Fortunately, because at the lowest point of Dutch elm disease, at least 1 died every year2022 to 2.04 trees!” says Paul.

Annual check

Our green managers, arborists and gardeners annually check all elm trees in The Hague. Between May and September, the elms are inspected twice. The team looks at the elms of the municipality and also the elms on private land. “We keep a close eye on the trees because if an elm is sick, it can quickly infect surrounding elms via the roots or via the elm bark beetle itself,” says Paul.

See a sick elm? Report it!

A sick person You can recognize elm by its dry, withered leaves. Over time, the elm loses all its leaves. If you see a sick elm, please report it to us. Here you can find more information about

how to recognize and report a sick elm.

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