I just noticed my Hackberry tree is being invaded by what I believe to
be mealybugs. The leaves have little fuzzy white spots on them. If
you look closely, it looks like a light mist of sap(?) is raining down
from the tree. Ants are attracted to this sticky substance. This
happened last season, and it got terribly sticky on the back porch. I
can't imagine it's good for the tree either. I think the onset of
winter finally killed off the little buggers, but now they're back
again.

What can I do to rid my poor tree of these pests?