How can I stop shrubs from browning out? They are mature yews (I believe), west facing, receiving good afternoon sun, approximately 5 feet tall and 25 feet across. They have started to turn yellow to light brown beginning at the tops. I originally thought it might be winter burn but I am not seeing any improvement, leading me to now suspect insects or disease. I have never fertilized them specifically in the seven years we have been here. The problem was first noticed, just slightly, last spring, but the damage didn't progress. This spring they have gotten much worse. What could the problem be and what can I do? Photos submitted. Thanks for your help.
We notice that your other yew (in the background of the photo with the azalea) looks fine. So the problem is would not be a general disease or insect because that would have spread to the other yews. Also, insects are not active in the witner.
Yews do not like "wet feet". When their roots stay wet too much, they tend to get root rot diseases. We see a downspout behind the yellowing yew. Possibly, that yew is getting too much water around its roots. Sometimes soil grade changes, etc. so that soil remains wetter than in the past. You might want to investigate that.
There isn't anything you can do about a root rot. You'd have to remove the shrub and plant with something that likes a wetter environment or fix the soil drainage to make it dryer.