Silver leaf may inspire memories of your great-grandmother’s tea service, but this fungal disease is anything but elegant.
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) but is found most commonly among 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. That silvering is the result of toxins released into the vascular bundle and carried to the leaves. [I was unable to find a photo I could use, but you can Google it.] These symptoms spread progressively throughout the tree, killing branches as it goes. Infected wood is darker than normal. 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.
Leaf silvering can also occur as a result of environmental stresses, such as drought or cold. This is called false silver leaf. If you cut into a limb affected by false silver leaf, the interior wood will be a normal color and not stained. Leaf symptoms may also be caused by whitefly feeding.
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.
Silver leaf management
Trees infected with silver leaf often die. There are steps you can take to prevent it from occurring in the first place. One method is to prune susceptible trees, especially cherries and plums, in summer. Rather than painting the surface of pruning cuts, allow them to heal naturally. Too often, sealants keep the wound from drying, which results in rots and other fungal diseases. And be sure to thin fruit to the point that branches aren't overburdened.
If an infection occurs, cut off the affected limb at a point 6” below the infection, sanitizing your cutting tool with bathroom cleaner between each cut. Infected wood should be bagged and tossed in the trash right away, as it is a source of further infection. Continue to monitor the tree closely for symptoms.
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