Silver leaf, caused by the fungus Chondrostereum purpureum, is a wood rotting fungus that frequently attacks apple trees, particularly those that have undergone major tree surgery.  The fungus has a wide host range including pear, stone fruit and many woodland, hedgerow and ornamental trees and shrubs.  All apple varieties are susceptible.

The leaves of affected trees show the characteristic symptom. of a silver appearance.  Whole trees or tree parts may be affected.

Once the tree or tree parts die, they become covered in fungal fruiting bodies which are 1.5-3 cm diameter brackets with smooth purple lower surface and pale brown hairy upper surface.

The life cycle involves the production of fruiting bodies on dead branches in autumn.  Spores are released from these during wet weather from autumn to the following June and infect trees through wounds.

Apple trees showing symptoms of silver leaf may recover.  Therefore, mark affected trees and monitor their progress.  Grub immediately the tree dies and before fruiting bodies are produced.

Control

There are no fungicides currently recommended as sprays for control of silver leaf. Bezel (tebuconazole) was previously recommended as a paint for application to pruning wounds for the control of Neonectria canker but this approval lapsed in 2015. Other coatings, e.g. BlocCade, provide a physical coating for protecting plant wounds against infection caused by fungi such as silver leaf. To be effective, wounds must be treated immediately after pruning.   Effective control is mainly dependent on orchard hygiene and cultural measures.

• Remove and burn dead trees before silver leaf fruiting bodies are formed.
• Do not stack wood from felled apple trees at the orchard edge as silver leaf fruiting bodies may form and provide a large source of inoculum.
• Check surrounding hedges and woodland for silvered trees and silver leaf fruiting bodies and remove and burn.
• Avoid pruning in wet weather when the risk of the silver leaf fungus infecting wounds is much greater.

Organic production

Control in organic orchards is dependent on cultural measures and good hygiene.

 

Wound protectant paint previously approved for use on apple – safety factors

	Hazards					Buffer zone
Active ingredient	human	fish + aquatic life	bees	Harvest interval (days)	Max. no. of treatments	Width (m)
Phsysical protectant (BlocCade)	u	u	u	Treat wounds shortly after pruning	u	N/A

d = dangerous; h = harmful; ir = irritating, a = may cause allergic reaction, t = toxic

PH = post harvest; Pre bb = pre-bud burst, sm=statutory minimum of 5 m for broadcast

air-assisted sprayers

u=uncategorised/unclassified/unspecified, c=closed cab required for air assisted sprayers