I am losing three or four of my border shrubs (yews I believe). These were...
I am losing three or four of my border shrubs (yews I believe). These were part of a long border that have been there before I bought the house so they may be over 40 years old. Two started looking bad in the late spring with some branch ends turning yellow and then brown. We were advised to remove leaves from under the shrubs and spray with Bayer Insect and Disease for spider mites. I did this several times, but there was little improvement. In the last 3 weeks, these two have rapidly declined to the point where I believe they need to be removed. I have two more along the line that are starting to look like they are declining. I had another across the yard which rapidly declined and died earlier this summer. I now have a six in the front of my house looking the same. I have never had this experience before but then again I'm not sure it rained as much as it had earlier. I have been advised that this could be a drainage issue or possibly phytopthera. I have attached several photos; can send several more to an e-mail address. Obviously, I'm concerned about the fate of the other bushes and what I might be able to use to replace the missing bushes and not suffer the same fate.
We only got the photo that looks totally dead, which unfortunately doesn't give clues about what can be affecting your yews. You're welcome to send the other photos in a subsequent email in which you can attach 3 photos. We need to see photos of declining parts, before they die.
Yews usually succumb to root problems. They hate to have "wet feet", meaning sitting in soggy soil. If the soil grade has changed or water runoff patterns have changed for any reason, either on your property or your neighbors, the roots can drown.
You can dig up a dying (not dead) shrub and inspect the roots. Healthy roots are white or light colored. Roots should not be black, smelly or mushy. We had abnormal rainfall and overcast cool days (which prevented evaporation), this spring, which may have caused root rots, too. This is especially probable because you say the first one died in late spring.
Any plant can die of drought, of course. If your plants lost some roots to rot this spring and early summer, then the extended drought we are having now may be pushing them over the edge because they are dealing with less roots to absorb water.
Thank you for the additional photos. They show no signs of insects of disease, Yews have very few problems, but they are susceptible to environmental and cultural problems. When you remove the plant, examine the roots carefully for any signs of stress. If they are black and limp, it would indicate root rot caused by excessive moisture. If they are sparse and brittle, it could indicate drought stress.