March 30, 2012
Read the info you provided about the insect. I am a little confused when you say they are basically harmless. Back east where I come from, they defoliated huge areas. Now I am living in Az. in an area where we have never seen them before, but I am suddenly inundated with them. They seem to be everywhere in mass quantities. They are climbing the Hackberry trees, our primary source of shade. Is it likely they will defoliate them? If so, what can be done? Thanks in advance for any info.
April 8, 2012
They can defoliate a tree, which is unsightly and annoying, but when we say that they are harmless, we mean that they don't often kill the tree.
The tent worm you are seeing in AZ is likely a different species than the one you saw back east (which would have been the Eastern Tent Worm). Yours in AZ at this time of year are likely Sonoran Tent Caterpillars.
You can try to stem them by locating and removing egg sacs from the tree. They will look like hard masses on the branches. You can also treat the worms with any pesticide that is effective on caterpillars.