Why Are My Cherry Tree Leaves Turning Silvery?

A silvery, metallic sheen on cherry tree leaves — as though the surface has been sprayed with silver paint — is the most recognisable symptom of silver leaf disease, one of the most serious fungal infections that affects cherry and other stone fruit trees. Unlike powdery mildew, which produces a powdery white coating you can wipe off, silver leaf silvering is structural — it results from the leaf surface layers separating from the tissue beneath — and cannot be rubbed away. Silver leaf is a notifiable tree disease in some regions, and it progresses without mercy if infected branches are left in place.

What causes silver leaf disease?

Silver leaf is caused by the fungus Chondrostereum purpureum, which enters trees through pruning wounds, cracks and damaged bark. Spores are released from bracket fungi (purple-brown, bracket-like fruiting bodies) that appear on dead wood of infected trees and stumps, particularly in autumn and winter. The fungus colonises the water-conducting vessels in the wood, releasing toxins that cause the leaf's upper surface to separate from the cells beneath, creating the characteristic air gap that produces the silvery appearance.

Confirming the diagnosis

Not all silvery leaves mean silver leaf disease. Pseudo silver leaf — caused by environmental stress, waterlogging or root damage — produces a similar appearance but without wood staining and without progressive dieback. The confirming test is to cut into a branch showing the silvery leaves. Use a sharp saw or secateurs to expose a cross-section of wood about 3 cm below the nearest point of silvery foliage. If there is brown or purple staining in the centre of the cut wood surface, silver leaf disease is present and the infection is active in that branch. If the wood is clean and white-cream, pseudo silver leaf from stress is more likely.

Removing infected branches

There is no fungicide treatment for established silver leaf infection. The only control is removal of all infected wood. Cut back the affected branch to at least 15 cm beyond any visible wood staining, checking each cut for staining before cutting further. Sterilise tools between every cut. Bag and remove all infected prunings immediately — do not compost. If staining reaches the main trunk, the tree is likely to die within a few years, though this is not always immediate.

Preventing silver leaf through pruning timing

Silver leaf spores are most prevalent in autumn and winter, when wounds also heal most slowly. Prune cherry trees in summer (July to August) only, when wounds heal rapidly and spore load is lower. Avoid making large cuts unnecessarily, and seal pruning wounds over 3 cm diameter with a wound sealant paste if pruning must be done outside the summer window. Remove any dead wood, stumps or infected material from the garden that could be producing spores.