pear pest, some kind of fly? - wooly aphids

My pear tree only produced one pear this year, needless to say it was probably quite stressed, as were all the other fruit trees in the orchard. The original planter planted them all too deep, and the soil is heavy clay. I decided to dig them out a bit to let them breathe since its been a soggy year and i expect they dont like drowning roots.

I got to the pear tree, and as I was digging, I noticed a weird fuzz from under the bark. On closer inspection, every crevasse in the bark is buried in these small flies with white fluff on them.

What are they? Are they harmful to the tree? Should I spray them now while everything else is dormant, and hope the tree is strong enough next year to resist them?

Those look like wooly aphids.

Here is one suggestion though there are several more like using a soap solution:

A strong jet of water every few days knocks them right back. I'd say try doing it in the morning so the tree isn't wet overnight, or you may swap aphids for fungus!

https://permies.com/t/13647/white-cottony-stuff-apple-tree

Thanks! It looks like theyve gone dormant for the winter. Ill try the soap solution, i doubt theyll survive if knocked off at this time of year as i can pick them off by hand and they dont even try moving!