Dutch Elm Disease - Conservation Management Plan - TD17 - B


A Devastating Fungal Disease - Elm Trees

Common name: Dutch elm disease.

Scientific name: Ophiostoma novo-ulm


Plants affected: Ulmus spp. (elms) and Zelkova.

Main symptoms: Wilting and death of foliage, branches and then the tree.

Cause: Fungus which is carried by beetles.

Timing: Damage usually seen summer to early autumn.


Symptoms of this deadly disease

You may see any of the following symptoms:

There is often very little obvious warning that a tree has been affected. As all our Elms have been on our acute watch list since the 1970's we have paid particular attention to them on a regular basis. We have always had the Elms marked out on our watch list as Specimen trees even if planted in commercial forests. 

If affected it is most visible in the  summer months. Suddenly all or often just part of the foliage of the Elm tree  turns yellow. The next stage is when the leaves wilt and shrivel up. There is no remedy and the tree eventually dies.


Peeling off the bark from affected branches will reveal brown streaks in the outer wood, which appear as a broken or continuous brown ring in the outer growth ring if the branch is cut across.

Where once Elm trees have grown Clandon Park have had no option but to plant resistant species of trees to replace the diseased trees that have been felled.


Controlling the Disease

Tree Disease Management for single trees and forestry:


Non-chemical control

According to our own Foresters and the Royal Horticultural Society, all attempts to prevent the spread of DED have been long since abandoned in the region. Dead trees are a serious safety hazard and should be felled promptly.

Our advise has been that native elms should not be planted in place of a diseased tree, as they will almost inevitably succumb to DED, so we have followed this advice. We generally avoid planting resistant hybrid Elms exactly in their place as we chose to rest the ground for some time before replanting and, in any case, the resistant forms have a different growth habit to those that have been lost and do not exactly replace them. 

Due to the risks posed by another  phytoplasma disease called Elm yellows phytoplasma (Candidatus Phytoplasma ulmi) Clandon Park has chosen not to replant using imported Elm trees. 

The Conservation Foundation have a Native Elm Programme for propagating elms from the survivors of the last disease outbreak. Anyone who knows of a healthy mature elm (at least 190cms circumference at breast height) or would like an elm to plant as part of the experimental programme is encouraged to contact the Conservation Foundation. 

Chemical control

No chemical control is feasible. Protectant fungicides were injected into trunks in the early stages of the outbreak, but this was required annually and soon abandoned as impractical. It is also completely impractical to control the beetle vectors. 

(Courtesy of the RHS)

Where single Elms trees once stood in coverts, woodland glades and forestry, other species soon inhabit their space. The great sadness is that the stately Ancient Elms of Clandon Park are no more because of this devastating disease that was apparently imported into this country in the 1960's . Our records show that our Elms started to be affected in the 1970's. 

Conservation Management Plan

Historic England Listing:

Clandon Park

List Entry Number: 1001171

Heritage Category: Parkland

Grade: II


Clandon Park Estate, West Clandon, Guildford, Surrey

All photographs curtesy of the Countess of Onslow. No photographs may be reproduced without her consent.