Q: I recently discovered that my neighbor's tree has a branch full of webworms. How quickly do they spread, and what do I do if I see evidence of them on my trees?
A: Fall webworms are caterpillars that especially like cherries, crabapples and most any fruit-family tree. They chew on leaves under the protection of webbing that usually starts at the tips of branches and works in toward the trunk.
This is a pest that looks worse than it really is. They're mainly cosmetic problems. Although they can chew up an area of leaves pretty well, the damage is late enough in the season that the leaves have done the bulk of their job for the year anyway. Webworms also tend to feed in patches – not defoliate an entire tree.
I wouldn't do anything if your trees aren't affected. You might not have any species that webworms like.
But if they start to feed on any of your trees, my favorite control is a big stick. Just whack open the webs and let birds in to have a webworm buffet.
If you can't reach the webs, a spray of the bacterium Bacillus thuringiensis is the least toxic way to control them. Also non-toxic to people and pets is the new spray Spinosad. It's the active ingredient in Capt. Jack's Deadbug Brew (among other brands).
You can also just prune off any infested branch tip and stomp on the caterpillars once you have them on the ground. Or just ignore the whole thing and go have an iced tea.