Strange white strings on cherry tree leaves
This sort of thing happened to one of my plants.  When I took a closer look at the plant, it was a group of white aphids.  The brown coloration of the leaves of your cherry tree was relevant because aphids can sometimes kill the entire plant that they feed off of.

I did not take a picture of the plant, but I found one online: https://entnemdept.ifas.ufl.edu/creatures/trees/shivaphis_celti03.jpg