I have a holly hedge that has small, white, rice-shaped deposits on the back of leaves. It looks like someone took paint and splattered it all over. It is most noticeable on the darker, older leaves, but is also on new growth. I have four other hollies in the yard, and they too are infested. There doesn't appear to be anything moving--mites, white fly, etc. But I am wondering if these are egg sacs or deposits for future infestation.
Certified GKH Gardening Expert
It is likely aphids. They don't move much. This article will help you:
Neem oil is an effective treatment for these pests. Here is additional info: https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm