My holly bush foliage seems to be less dense this year and I've noticed some black spots on some of the leaves. Do you think an insect or disease is causing this? Thanks very much for your advice.
Certified GKH Gardening Expert
It sounds like it may be tar spot. This article will help you learn more: https://www.gardeningknowhow.com/ornamental/shrubs/holly/holly-problems-holly-leaf-spot-or-holly-tar-spot.htm