Cottony Maple Leaf Scale, a relative of mealy bugs, is common this time of the year in the Northeast. See the post below by clicking on the link.

"In the Northeast, it could also be Cottony Maple Leaf Scale. I was communicating with someone who lives in New York State and she took similar leaf samples to her Agric Extension Office where they identified that pest as scale. This type of scale is related to mealy bugs so anything you use against one of them can also be used against the other. If the infestation is still growing, Imidacloprid could help but if the pests have left then the insecticide may not do much since they "left the nest" already. I personally would apply it once any way this year. But then I would start reapplying it next year about 1-2 months nefore this time of the year. If you prefer a more organic solution, you could squish them by hand, release beneficial insects such as lady bugs (beneficial insects) or apply insecticidal soaps, Safer's Ultra Fine oil, etc .etc instead of using Imidacloprid. Do not use both, the insecticide and the beneficial insects, at the same time because the insecticide will kill them."

Here is a link that might be useful: Scale infestation