Hi, Tessa, There is no chemical control for silver leaf. You have to cut away infected wood, cutting at least 6 inches beyond infected wood. You know it is infected if, after cutting, you see a brown stain in the wood. Do this in summer and make sure to sterilise your tools after pruning and burn the infected wood. You can paint the cut areas with tree wound paint to keep the fungus from re-infecting the tree. Feed the tree. If the fungus is in the main trunk, there is nothing you can do so it is best to remove the tree. Kathy C