Usually, April and early May in SE Texas landscapes is the time of the year when we see masses of worms/caterpillars clustered on tree trunks working their way up to the leaves, only to devour them in a week or two. What you’re seeing in these pictures, are affectionately known as Tent Caterpillars.
First, relax, because this is not life-threatening to the tree. It’ll make it ugly for a month or so but will not kill the trees. Secondly, if you can catch them in these clusters on the trunks, blast them with an insecticide.
If you can, spray a bit of Bt (Bacillus thuringiensis) up there. Everything you need to know about Bt, we have online already here: Bt – The Whole Story If a worm or caterpillar takes a single bite of a Bt treated leaf, it will be its last bite period.
Technically, to get true control of any leaf munching caterpillar or worm, if you can kill it at the main source and back up your protection organically with Bt, you’re serving up insect control in the best of both worlds.
If you see this hideous sight, don’t panic, just get busy! Don’t blow it off, because while the worms may be a natural food source for birds, I’ve never seen birds eat enough of these icky things to prevent the leaf destruction.
And if you’re wondering, I do believe these are very cyclical insects, where we will see them one year but not the next. And they can be set back by a severe winter freeze. Winter Storm URI knocked out many over-wintering insects that were exposed in February of 2021.