Grey Mold on Trunk and Stems
My 9 year old pot grown Maple has developed a grey coloring on its trunk and some stems. About a third of the tree hasn't produced leaves this spring and a lot of the branches have only a few leaves on them. Usually it's a mass of new growth. I repot every couple of years. It's in a big wooden half barrel.
Certified GKH Gardening Expert
The grey growth is likely lichen. It is not the cause of the trees problems, but rather a symptom. They tend to attach to trees that are sickly and unhealthy. This article will give you more information: https://www.gardeningknowhow.com/ornamental/fungus-lichen/treatment-tree-lichen.htm In regards to what may be wrong with the tree, I would take a look at the roots. You may have some root rot or the tree may need to be repotted. It may also be a fungus attacking the tree, so you should go ahead and treat the tree with a fungicide, which will actually also get rid of the lichen.