Holly Bush Disease
The huge holly bush in my neighbor's yard is covered with a white fungus or larvae on the leaves. As this overhangs the fence between us, I am concerned it will drop and infect my plants. The lady gardener says it is not white fly.
Certified GKH Gardening Expert
Are the areas powdery in nature? If so you are dealing with powdery mildew. Here is an article that you may find helpful: https://www.gardeningknowhow.com/problems/get-the-cure-for-powdery-mildew.htm
If not, it could be scale or mealybugs, both of which could be treated with neem oil (as can powdery mildew). I have found it to be very effective against these pests. Here is more information: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
For additional information on scale bugs, which commonly affect these plants, here is an article that you may find helpful: https://www.gardeningknowhow.com/plant-problems/pests/scale-bug-how-to-control-plant-scale.htm