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Dutch elm disease

The impact of Dutch elm disease (DED) has been worst in parts of the country where the predominant species was the English elm, whether in hedgerows or planted as a street tree. English elm does not reproduce from seed in Britain and all existing trees were probably derived from a handful of original specimens. Many clumps and rows actually started as root suckers from a single tree. In this situation, the fungus that causes Dutch elm disease can be transmitted from one infected tree through the common root system, so that the others go down like skittles.

The stumps of many hedgerows that apparently die or are felled because of DED remain alive and eventually produce new young trees as coppice shoots or root suckers – not genetically new but a clone of the original. They usually grow quite happily up to five or six metres and then become dramatically re-infected in large numbers. This delayed but apparently rather sudden reappearance of disease reflects the population dynamics of the beetles that spread DED. They breed in elm bark, needing fairly thick bark to do so successfully. In a landscape denuded of large elms, the beetle population falls to a low level and the disease does not spread. Once the sucker re-growth gets to a suitable size, however, the beetles and the disease move in again.

Find further advice on the maintenance of trees on council land and tree preservation orders.

Report a diseased tree