Advice

RHS Help & Advice

Clematis wilt (Phoma clematidina)

Symptoms

One or more shoots wilt and die rapidly, starting at the shoot tip or a leaf and spreading downwards, even as far as the base. The leaf stalks blacken when infection spreads from the blade and freshly infected stems blacken internally.

Some large-flowered cultivars are particularly susceptible. Smaller-flowered species such as Clematis montana are generally resistant.

Wilting can also be caused by waterlogging, root diseases, graft failure, wind, insect or slug damage. However, the symptoms are not as localised in these cases and other symptoms do not appear. If in doubt as to the cause of wilting it is worth having the plant examined by experts, as different action will need to be taken in each case.

Cause

This disease is caused by the fungus Phoma clematidina. Spores are produced from tiny fruiting bodies on the infected stems, and are spread by water splash. The fungus can remain in the soil for many months in old infected plant tissue.

Control

Cut back the wilted shoots to healthy tissue. This may mean pruning below the soil surface.

The plant does not need to be dug out because new shoots may develop below the wilted section later in the season or the following spring.

There are no fungicides approved for home gardeners for control of clematis wilt, but the fungicides myclobutanil (e.g. Systhane Fungus Fighter) and penconazole (Scotts Fungus Clear) are labelled for the control of other diseases of ornamentals, and could be applied to control wilt at the owner’s risk. These products have been cleared for use on ornamentals as a spray (NOT for soil application) and are therefore safe to the operator when used as directed. If parts of the plant remain above ground after cutting out the diseased parts, an application at a dilution suggested on the packet for other problems may be useful, but there is no guarantee of efficacy.