White ash-like substance on Hawthorne and Beech?

Hello,
I have a strange, white, ash-like substance on the leaves of my Chinese hawthorne and European beech trees. They look healthy except for this soft white stuff, which hangs on the outside of the leaves and falls off if I shake the leaf or touch it. Does anybody have an idea about this?
Thanks,
John S
Portland

 

John--my tricolor beech gets these pretty regularly too.

Wooly aphids. Try squishing some of the "ash" between your fingers and you should get some mushed up aphids. I've never worried about them as the tree is too vigorous where it is anyway.

An insecticidal soap would kill them, but it's tough to get it to soak thru the "wool", have to hit em pretty good. Probably just as easy to "blast" the tree with strong hose pressure and knock a lot of it off with just water. If you're worried about the trees, or the infestation gets too bad...Otherwise let the ladybugs build up enough to keep them manageable (?)

Glen

 

Spellcheck: Hawthorn.