The leaves of infected plants take on a silvery sheen. Infected branches have brown staining in the wood; you can see this in the grain when you cut an infected branch off the tree. The disease can start in a single branch which will begin to die back. If not checked, it will kill the whole plant
Silver Leaf attacks a range of fruit trees (most famously Victoria Plum) including plums, damson, cherry, peach, apricot, pear and apple. It can infect a few other trees such as Laburnum, and poplars but it mainly attacks members of the family Prunus (which includes the laurels).
Silver Leaf (Chondrostereum purpureum) is a fungus whose spores penetrate a trees defences through recent wounds such as snapped branches and pruning cuts. The spores grow fungal threads, which penetrate living wood, killing it as they proceed. The silver leaves are caused by a poison which the fungus releases that causes the outer cells on the leaf to separate resulting in the silvery sheen from which the disease gets its name. The silver leaves are in no way infectious themselves. Silver Leaf spores are produced in small, tiered, purple/brown structures with a white, rather woolly top that grow on dead wood on standing trees and on stumps and logs. The spores are the cause of new infection which generally break out between September and May.
Don't Prunus. Hang on to the thought. You can prune all fruit trees in winter except any whose Latin name begins with Prunus. So in Winter DON'T PRUN-US. It is much easier for silver leaf to enter a wound in a tree when the sap is not rising. So Prunus species (which are all potential victims) are best pruned when they are in growth and when the wound will bleed, clot and seal itself.
Prevention is always better than cure. Well planted trees, in good soil, which are staked so the tree does not rub the stake, which are protected against strimmer and lawnmower damage and which are mulched with good organic matter every spring are far less likely to get silver leaf in the first place.
Keep orchards clear of dead wood and always remove or grind out the stumps of dead trees. There is no chemical cure for silverleaf.
If you can catch it early enough and it has only infected a branch, then remove (and burn) the infected material. Cut the branch off below the visible infection. Check the cut and if you can see a brown stain in the wood, remove more of the branch until there is no stain. Then cut off another 6 inches and paint the wound with a sealant such as Medo or Prune n Seal. Disinfect the saw blade with Dettol, Jeyes Fluid or meths BETWEEN EACH CUT.
If the strain has reached the main trunk the tree will die and it should be removed and destroyed as soon as possible to prevent it infecting other trees nearby.