Beech (Fagus)-Aphid

Several species

See:

Common Pests of Nursery Crops

For more information

Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 296).

PNW Nursery IPM: Woolly beech aphid (https://agsci.oregonstate.edu/nurspest/aphids/woolly-beech-aphid)