There are three sections to this article:

1. The symptoms of Silver Leaf disease.
2. Treatment and prevention of Silver Leaf disease.
3. The life cycle of the disease

SYMPTOMS OF SILVER LEAF DISEASE

The symptoms of Silver Leaf disease need to be investigated carefully because the treatment can be quite drastic and the disease can be mistaken for environmental conditions. Use the next couple of paragraphs to positively identify this disease. The key symptoms are:

• A silver sheen to some of the leaves. Consider other causes if the majority of leaves have a silver sheen to them. A closer look at the affected leaves will show that they have nothing on their surface which might be the cause of the apparent colour change. See lower down for the reasons why the leaves turn silver.
• Some branches may well die back. You may or may not realise it but affected branches will be those which were incorrectly pruned or damaged in the previous year(s).
• Affected branches may have fungi on them, these fungi are sometimes referred to as fruiting bodies. These look a bit like flat toadstools. They can vary in size and shape. Initially they are a purple coloured but they turn brown in summer.
• If you cut through an infected branch which is greater than 3cm / 1in wide there will be dark brown marks in the wood. If these aren’t visible try wetting the wood which often makes the brown marks become more visible. These brown marks are the most positive sign of Silver Leaf disease and are rarely caused by anything else.

The leaves of an infected tree are not infected by this fungus it is only the wood which is infected. The silver sheen to the leaves is caused by the top layer of the leaves separating from the layer below as a reaction to the fungal infection in the bark. When the two layers separate light is reflected differently making the leaves look a different colour.

Leaves with a silver sheen to them

It is important to realise that a silver sheen to leaves is not always caused by Silver Leaf disease. It can also be caused by environmental factors such as late frosts when the leaves have formed. Always look for other signs of the disease as well such as the marks in the wood or dead / dying branches. Also, environmental factors tend to affect the majority of leaves on the tree very quickly whereas Silver Leaf disease tends to be restricted to areas around the infected branch although if left untreated it will spread beyond that area.

TREATMENT AND PREVENTION

Treatment of Silver Leaf disease is based on the following factors

• This is a fungal infection that affects the wood of the tree.
• Removal of all infected wood is the only treatment possible.
• If the fungal infection reaches the trunk of tree then the entire tree is affected.
• The infection spreads throughout the tree via the sap in the wood.
• The infection can be spread to nearby plants (plum, cherry, rhododendron, fruit bushes and more) via spores.

The treatment for Silver Leaf is simple but brutal. All infected wood needs to be cut back to healthy wood – about 3cm / 1in further than marks in the wood. All prunings should be burnt to avoid re-infecting the tree and other nearby plants.

In some cases Silver Leaf disease cures itself but there is no known reason why this occurs. The choice between hard pruning and leaving the tree to fend for itself is yours. If there are other susceptible tree / plants nearby then in almost all cases, hard-pruning is the only option to avoid the risk of the disease spreading.

If you end up with the situation where you prune branches away and they are still marked at the point where they join the main trunk of the tree then it’s really time to give up, dig up all the tree including roots and burn everything.

Silver Leaf Disease can be transferred from one tree to another by using unsterilised saws, secateurs etc. So be sure to sterilise all pruning tools after using them. Jeyes Fluid is an ideal and cheap cleaning solution. Leave it on the tool surfaces for 20 minutes and then rinse or wipe off.

Preventing Silver Leaf disease is simply a matter of caring for the trees as best as you can, see our article on caring for plum trees. Key to this care is pruning your plum or cherry tree at the right time of year. Late May to mid July are the best times to prune plums and cherries if you want to minimise the risk of infection. As soon as you get into August the risk of infection increases as time passes. Pruning in late summer and autumn also deprives the tree of the goodness stored in the leaves which may reduce its health in subsequent years.

One plum tree in particular is prone to this disease and that is Victoria, and in particular when grown on the “Brompton” rootstock. The rootstock “Pixie” has good resistance to Silver Leaf even for Victoria plum trees. It is dwarfing, very widely available and an excellent choice.

LIFE CYCLE OF SILVER LEAF DISEASE

Silver Leaf is a fungal disease that is active above freezing temperatures and spreads through spores which are windborne. The key lifecycle stages are:

• The fungi, which grow on infected branches, release spores in autumn and early winter when conditions are wet and and above freezing.
• If the spores land on damaged wood they will enter it and infect the branch. Spores can be spread several miles if conditions are correct for them. Typically the damage has been caused by pruning late in the year or branches which have broken.
• The infection spreads slowly throughout the tree wood and will cause changes in the leaves although the leaves themselves are not infected.
• When stems and branches are killed by the infection, fungi begin to form continuing the life cycle.

REPLANTING PLUM TREES AFTER SILVER LEAF

There’s no hard evidence about whether it’s OK to replant a new plum tree in the same place where a tree has previously been infected with Silver Leaf. Possibly the reason for this is that most experts would not recommend planting a new fruit tree in the same position as a previous one whatever diseases have been present. So the short advice is no, don’t plant in the same position. If there is no other alternative make sure all of the stump of the old tree is removed including the roots and replace as much of the nearby soil as possible with new soil.

If you have any questions about Silver Leaf Disease or general comments about this article, use the form below to send them to us. We will get back to you as soon as possible.

MORE PAGES ABOUT GROWING PLUM TREES:

HOW TO GROW PLUM TREES

HOW TO PLANT A PLUM TREE

CARE AND PRUNING PLUM TREES

PLUM TREE PESTS AND DISEASES

PLUM TREE POLLINATION GROUPS