Hi Beautifulboy! They sure look like mealy bugs to me, I know houseplants and other outside plants get them. I'm sure someone else on this forum would have a solution as to how to get rid of them. Good Luck,

Donna

Looks like mealy bugs to me also. Just my opinion here...
I would at least try to blast them off as much as you can
and spray with Sevin. Someone else might have a better
idea.
Margaret

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.

thank you everyone! we are getting to work on the project -- maybe this is a question for the organic forum, but I am curious, do ladybugs really work?

BEWARE!!!!
It's definitely cottony maple scales. During the last two years infestation in Northeast become somewhat epidemic.
It started on Long Island, NY and spreading north along the coast.
Not easy to cure and requires two applications of Safari or Meritt (first in early spring when plants are in a leafless stage and another during the hatching period of scales) for at least two years on a row. At least!
The most succeptible shrubs/trees:
Jap.maples, Cornus florida and C. kousa, Hydrangeas (all beside paniculatas), all Prunus family, Hollies (some), Ilex glabra, Styrax (all).

That does indeed look like cottony maple scale.

Ego45 do you say beware because cottony maple scale may kill my hydrangea or because it may infest other bushes in the area? (or both?)

Unfortunately because we have a toddler and because the hydrangea is near the deck using chemical pesticides is not an option for us. We will have to find a less toxic approach. I'm searching for solutions now...any ideas?

Beware because it spreading fast and could affect many plants in your or neighboring yards.
This scales will not kill mature plants, but will cause a lot of dieback on thin branches and twigs. Leaves containing eggs will fall and spread plague all over.
Regarding toddler and chemicals.
Neither Merit nor Safari will do any harm to a baby for as long a he/she will be inside during the application. Within 2-3 hours after spraying it's absolutely safe for anyone to be outdoor.
Unfortunately there is no such thing as an organic remedy against CMS.

A friend advised that I should try to use hortoculturalist's oil (nursery oil) twice--one application in the fall and one in the spring. This will suffocate the bugs. Any thoughts o this approach?

Fall application (of anything) is useless against the scales.
Make your own research about life cycle of the beast and then consult with the real professionals.

Spray your plant (on a cloudy day) with a solution of 40 parts water, 1 part liquid dish soap and 8 parts rubbing alcohol......This will kill the scales. Hose off the plant the next day to wash off the dead scales......you may have to repeat this in a day or two if you missed some.

Ian