Phytophthora root diseases

Symptoms - Phytophthora is a genus of soil-borne fungi which cause root rot of herbaceous and woody plants.

On affected trees cracking or bleeding cankers occur at the base of the trunk or higher up, where complete girdling leads to rapid death. The symptoms on viburnums are wilted stems leading to death, signs are seen at the base. Rhododendrons develop a twig and leaf blight - twigs become brown to black, usually starting at the tip and moving towards the base; the leaves show dark brown blotches.

The spores overwinter in the soil and can be moved around in run-off water from field sites or from potted plants carrying them. There are no treatments to clear up infected plants so they should be removed and destroyed. If practical the soil can be fumigated to a depth of 15cm before replanting. There are some fungicides which can be used on healthy plants as a preventitive. Seek professional help.