This looks like cottony camellia scale on the foliage. This is a soft scale, a sucking insect. Honeydew and sooty mold are the major problems caused by this insect.
In june, females die and may fall off, leaving only white ovisacs. Immatures hatch through June and remain on the underside of leaves or bark through the winter.
At this point, we recommend that you spray with a dormant oil after leaf drop. Follow label directions.