Eriococcus azaleae
See:
Pest description and crop damage White, cottony sacs enclosing small, reddish eggs.
Management-chemical control
See:
Chemical Control of Nursery Pests
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 336).
PNW Nursery IPM: Azalea Bark Scale (https://agsci.oregonstate.edu/nurspest/insects/azalea-bark-scale)