Sweetgum Defoliator Caterpillars
Q: About a week ago I noticed very small black pellets falling from my sweetgum trees. Upon further inspection of the trees, I noticed the crowns appear to be eaten away.
There appears to be a rather extensive infestation of some type of caterpillar in my trees.
A: Congratulations! You’ve presented my first ever report of an insect whose common name is simply “sweetgum defoliator”.
The last time this creature was noticed was in 1977 when lots of sweetgum trees in middle Georgia were defoliated.
Forester Terry Price took pictures of the damage and identified the insect as Paectes abrostoloides. This small brown moth lays her eggs in early summer on the host plant. Caterpillars hatch from the eggs and begin feeding, leading to the droppings you noticed.
Terry noted that a virus appeared to wipe them out by the end of the outbreak. Since this only happens once in a blue moon, I don’t think you have much to worry about.
Read more here.