Silver leaf

Silver leaf is a destructive plant disease caused by the fungal pathogen Chondrostereum purpureum. This fungus primarily infects the vascular system of trees, leading to the decay of wood and, in severe cases, the eventual death of the entire host plant.

The fungus has a wide host range, commonly impacting fruit trees such as apple, cherry (including sour cherry), apricot, pear, almond, peach, and raspberry. Infection typically occurs through fresh wounds, such as pruning cuts or storm damage, where fungal spores land and colonize the sapwood.

The primary symptom is a distinctive metallic or silver-sheen appearance on the leaves. This occurs as the fungus releases toxins that cause the leaf epidermis to separate from the underlying tissue, creating air pockets that reflect light, resulting in the characteristic silvery coloration.

Environmental conditions play a crucial role in disease development, as high humidity and rainfall favor spore germination and spread. The fungus is most active during spring and autumn, making these periods high-risk times for pruning, especially if tools are not sterilized.

Effective management and prevention of Silver leaf require a combination of sanitation and vigilance:

• Prune during dry, favorable weather conditions.
• Always sterilize pruning tools between cuts on different trees.
• Promptly remove and dispose of infected branches by burning.
• Seal all large pruning wounds with suitable wound paint to prevent spore entry.
• Monitor trees regularly for signs of leaf silvering or fungal fruiting bodies.