I get that quite a bit in my area. It's pine bark adelgids.

Mostly harmless unless it gets pretty bad but on a newly planted or smaller tree, I wouldn't let them get too well established.

I generally just use the garden hose and water.

Not any extremely high pressure, but enough of a spray (mist or flat?) to where you see the water washing most of the white stuff off the branches.

After a few times of doing that, they tend to not come back very strong for a good while.

Thanks for the response bill! appreciate your expertise