These are both scale insects, but different species. On the azalea, they are Azalea Bark Scale. Based on their life cycle, it will be about a month until the crawlers (newly-hatched juveniles) appear for this type of scale. At that point, they will be very vulnerable to a treatment of horticultural oil (neem being one type in this category). Until that point, hort. oil treatments might have limited affect. Sprays will need to contact the scale directly by coating the leaf undersides, so that might be difficult to achieve. Re-treatment can be done according to product label directions; often it's about 1-2 weeks apart.

The hydrangea scale is harder to identify because there are several species that look nearly identical to each other. Cottony Camellia Scale, Cottony Maple Scale, and Cottony Cushion Scale are all candidates; our guess is the latter, but we can't be certain. (Despite having particular plants in their name, the first two scale species can occur on plants other than camellia and maple.) Since we can't say when the crawler emergence period is with this one (since we don't know which exact one it is), you can just watch for them moving around before applying the same kind of oil treatment. Crawlers are very tiny but will be visible to the naked eye, and easier to see with a magnifying glass. They will look a bit like a mite, and they won't be moving very quickly.

To limit the amount of hort. oil needed, you can also squish them with your fingers or rub them off of the foliage under a plain water spray from a hose. Scale do not move very far or very fast (when they move at all), so knocking them off the plant will greatly reduce the population by itself without the need for any pesticide.

Miri