The brown does not look like mould or a fungus. It is forming on the mature leaves
11 September 2012 12:50 AM
Hello Gardening Friend
Mulberry trees can suffer from two main diseases - fungal leaf spot and bacterial leaf spot. The brown spots on the foliage of your mulberry plant may be indicative of fungal leaf spot.
Bacterial blight on mulberries (Pseudomonas syringae) and fungal leaf spot on mulberries (Phloeospora maculans). Both diseases cause defoliation on your mulberry tree and can occur at the same time on the same tree.
What you need to know is that the fungal leaf spot only affects leaves. They show small dark brown spots that have a green or yellow halo, gradually becoming larger. The leaf slowly dies, turning white with dark brown margins and the fungus then spreads throughout the tree via wind and rain splash. What you need to do, to care for your mulberry tree is practice good hygiene. This will help to solve the problem, raking up fallen leaves and keeping good air flow through the tree.
Bacterial blight on mulberry trees is a more serious problem because it affects the new shoots and leaves. Newly emerging leaves in spring will have large angular brown or black spots that are surrounded by a yellow halo, and leaves become distorted and curled. Cankers will develop on stems that die back. Bacteria oozes from these cankers and spreads through the tree.
We recommned that in autumn prune off all the dead wood and remove any infected material off site. You can spray with Yates Liquid Copper Fungicide, getting to the trunk and as high as you can manage. Hygiene is vital to help control the spread.