Viburnum (Viburnum)-Bean aphid

Aphis fabae

See:

Pest description and crop damage Black aphid on underside of leaves on Viburnum species referred to as "Snowball." They do not attack Viburnum davidii.

For more information

Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 300).