Silver Leaf

Chondrostereum purpureum

Silver Leaf

Chondrostereum purpureum 051120A by User:Strobilomyces (CC-BY-SA-3.0)

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Silver leaf is a severe disease of Plums, but it can infect many of the Rosaceae family, including Apple, Apricot and Cherry trees, Rhododendron and Laburnum species. The main symptom of Silver Leaf is the foliage developing a silvery tint. Although, this isn't true for Rhododendron and Laburnum plants, and is most notable in Plum. Other notable symptoms are a darkened irregular stain which can only be seen when cutting through the branch and bracket fungi appearing on older branches. Cold and drought can cause similar symptoms to Silver Leaf, and this is what's known as False Silver Leaf. The irregular darkening of the bark is a definitive way to identify silver leaf from the false form.

Identification

Leaves have a silvery sheen. This usually starts in one place and spreads down the tree. As it progresses, leaf margins and around the midrib may split and turn brown. The wood of infected branches turns a dark colour which is one of the ways to determine if it is silver leaf or false silver leaf. After this discolouration, the branches start to die back. During the summer after branches have died, small bracket-shaped fruiting bodies form on the bark. The disease will often spread through the whole tree and kill it if it goes untreated.

Growth factors

Poor soil conditions, poor air circulation.

Symptoms

Silvery sheen to leaves (mainly in plums)

Darkening of bark

Dieback of branches

Lilac bracket fruiting bodies

Biological treatment

Some trees can get over it by themselves. No need to destroy leaves as they do not carry the fungus. If branches begin to die back, then remove them and burn them, making sure to read and follow government guidelines before doing so. If the whole tree has silvered, that means that the entire tree, including the roots, is infected and should be uprooted and burned to prevent further spread. This may require the help of a professional.

Chemical treatment

There are no chemical treatments.

Lifecycle

Spores from the fruiting bodies infect trees through wounds in the wood they do not infect the leaves. The spores are most active between September-May (UK). The fungus produces toxins that are taken up through the tree which causes the leaf tissue to separate, air then enters the leaf which causes the silvery sheen.

Prevention

Good hygiene around plants e.g. clearing dead material from tree bases. Growing resistant cultivars. Not over-fertilizing. Having good drainage. Pruning in late spring-summer rather than autumn or winter is recommended as this when the infectious spores are produced.