I have a flowering dogwood with green moss (light in color) on trunk and branches. Some parts of tree branches dying. Some branches without leaves looking dead. What should I do?
We suspect that what you see on the dogwood is lichen. See the "speckled shield lichen" on this webpage: https://extension.umd.edu/learn/i%E2%80%99m-lichen-it-peak-season-lichen-peeping
Lichen does not harm a tree, but if you see a lot of it on a tree it can be an indication that the tree is declining for some other reason.
Prune out all dead branches. Water during droughts. Mulch, keeping the mulch from touching the trunk. As it the mulch decomposes, it will feed the tree. You can also spread organic amendments around the tree.
Dogwoods are forest understory trees and like a partial sha
de location and an organic soil. Try to replicate those conditions.