Holly Disease - Olney, MD
We have China Girl and Boy Hollies as foundation plants. They face west and get full sun. Over the last 1-2 years this pyramid plant has lost most of its leaves. I noticed a scale on some branches. Some branches seem to be dead. Other branches are still alive but have no leaves. 0665.jpg is the west (full sun side) 0664.jpg is the south-east side (shady side) 0662.jpg is the scale/dead branches Is there a recommended treatment? Will the plant generate new leaves on these branches.
Montgomery County Maryland
There is a test you can do to determine whether the branches are dead or still alive. Use your fingernail to scratch away the surface of the bark on a branch. If you see any green tissue underneath the brown outer bark, the branch is still alive. If you just see gray or brown, it is dead. You can prune out dead branches at any time.
The light blue patches you see on some of the branches are lichens. They can be found on dead or live branches and do not cause harm to a plant. https://extension.umd.edu/hgic/lichens-trees-and-shrubs
We had our plant pathologist look at your photos. Hollies can suffer from root decline and we think that might be what is happening in this case. There is no treatment for it. All you can do is prune out dead wood. Unfortunately, with significant pruning, it can take a long time for these to grow back. It's up to you whether you want to do major pruning and shaping or replace the plant.
Thank you for your reply.
Is root decline associated with a plants's age? These hollies are 30 years old.
Root decline is not generally associated with a holly's age. It is usually due to a change in the root environment -- to much water, too little water, mulch that is too deep, something in the soil restricting root growth, etc.