Tea scale, Fiorinia theae, is common on camellias. It is an armored scale that lives on the
underside of leaves. You can find it on almost any camellia by looking for inner leaves that have yellow spots on top. When you turn it over you will see tan canoe-shaped scale covers and some white fluff from the males. These are tough to treat because the heaviest infestations are often deep within the foliage of large bushes. You can find a Insect Note with more information and recommendations here.