Don’t let these caterpillars surprise you.
“Neil, what are these caterpillars, and will they kill my tree?”
I get inquiries many times each spring about these unusual insects. Gardeners find them massed on their trees’ trunks, and when I tell them that they’re “forest tent caterpillars” they usually wrinkle their noses and exclaim, “But where are the tents!”
These pests are closely related to eastern tent caterpillars, with one of the chief differences being that these don’t produce any kind of a tent. They just hang out on the trunks and stems.
Here is a great piece of information from my friend Dr. Mike Merchant. Mike retired a couple of years ago from Texas A&M and the Texas AgriLife Extension Service. Mike wrote that these are easily controlled with B.t. or Spinosad if they’re doing obvious damage, but by the time they start to congregate on the trunk of your tree, they may be about to stop feeding. Birds will probably find them.
If you want to read more – written by a real entomologist – read Mike’s piece linked above.