Yelowing holly tree
We have two holly trees in the front yard. They are both about 15 feet tall and are about 6 feet from one another. They get full sun. One seems to be yellowing. It had scale a couple years ago, so we treated both with systemic treatment and we sprayed them with horticultural oil. We treat them each spring and fall with Holly Tone. We are concerned with the yellowing of the leaves on one of the trees. Not all the leaves are yellow, but much of the tree appears affected. There are yellowing branches both high and low on the tree. Both trees have lots of berries this year. I've attached a few photos showing the yellow leaves and the contrast between the yellowing tree and the other (dark green) tree that appears healthy. What do you think is causing the yellowing? And should anything be done about it. We don't want to lose these trees. Thanks for your help.
Anne Arundel County Maryland
We viewed your photos but they did not show a particular problem. This looks like it may be a type of root issue but we cannot say for sure. Look around the base for excessive mulch, planting too deeply, girdling roots, vole damage http://extension.umd.edu/hgic/voles, possible sapsucker damage (can girdle branches) http://extension.umd.edu/hgic/woodpeckers-and-sapsuckers, scale insects (we do not see sooty mold on the leaves but you can look), poor soil drainage, etc.
You can also contact several certified arborists for an onsite diagnosis and the best way to proceed. http://www.treesaregood.org/