Holes in Rhodo leaves

I was going to say it looks like an out of control smoker dropping hot ashes.

Seriously, I have no experience with Rhododendron pests but that looks like insects for sure.

Look UNDER the leaves. If you don't see anything in the daytime, try again with a flashlight at night.

Google suggests it's weevils:

Leaves with crescent shaped holes are the handy work of the Cranberry Rootworm, Rhadopterus picipes. It chews holes in the leaf, some of which are crescent shaped. Cranberry Rootworm, Rhadopterus picipes, are shiny and black with a greenish sheen, these beetles are about 3/16 inch long. They feed at night and hide in litter or under containers during the day. Beetles damage leaves by chewing oval-shaped holes. They are usually associated with container nursery stock in areas with dense shade. Remove ground litter and weeds from the area and reduce shade where possible. Treat late in the day and repeat once or twice weekly.