Q: My father has 4 large (each 8 ft x 8 ft) Yews on the west side of his home. The far north Yew has developed some browning, which is getting worse as we get into autumn. It appears that on some sections of the bark there is a "mold" of some sort. Grey growth, sort of like a center circle with "arms" that spider out from the center. Could this be mold, insect invasion, weather damage, the cause of the browning? He would like to save the yew which about 60 years old.
Sue, If you want to save this tree I suggest you have an on-site inspection for a certified arborist - tree doctor. Whatever is causing the problem may spread to the other Yews. Best And Happy Yardening, Nancy.