Silver Leaf

Silver leaf may inspire memories of your great-grandmother’s fancy tea service, but this fungal disease is anything but elegant.

Silver leaf fruiting body (Strobilomyces) CC BY-SA 3.0

Silvering leaves spread throughout an infected tree and can lead to tree death. Caused by the Chondrostereum purpureum pathogen, this disease infects many members of the rose family (Rosaceae), most commonly apples and pears, plums, and other stone fruits. It can also occur on alder, beech, birch, buckeye, hawthorn, larch, maple, poplar, spruce, and willow, so these trees should be monitored for the disease, as well as rhododendron.


Silver leaf symptoms

The leaves of affected limbs slowly turn silver or bleached. Silvering occurs when toxins are released into the vascular bundle and carried to the leaves. These symptoms spread progressively throughout the tree, killing branches as it goes. Infected wood is darker. A whitish crusty area may also be seen on the bark. This is the actual fungus. If you look closely, you may notice the edges are purple. The body of the crust feels rubbery and may be covered with white hairs. After the fungal bodies have fruited, this crust turns beige or brown.


Spores float on cool, moist breezes. When they land on freshly exposed sapwood, the infection begins. That sapwood may have been exposed due to pruning, herbivore damage, a playful child, or too much fruit.


Other causes of leaf silvering

Environmental stresses, like drought or cold, can also trigger leaf silvering. This is called false silver leaf. In this case, the interior wood remains normal. Leaf symptoms may also be caused by whitefly feeding.


Silver leaf management

Trees infected with silver leaf often die. Use these steps to prevent it from occurring in the first place:

• Prune susceptible trees, especially cherries and plum trees, in summer.
  
• Leave pruning cuts untreated and allow them to dry and heal naturally.
• Thin fruit to prevent overburdening branches.

If an infection occurs, cut off the affected limb at a point six inches below the infected area, sanitizing your cutting tool with a household cleaner between each cut. Infected wood should be bagged and tossed in the trash to prevent further infection. Continue to monitor the tree closely for symptoms.