That would be the Fall Webworm, a cousin of springs Eastern,or Western, Tentworm caterpillers. Early in the life of these sprays of Bacillus thuringiensis - Kurstaki are an effective control, but even though the webs in trees look really bad they do no harm to the trees.
If one were to put a sticky band around the susceptible trees trinks in early July Ma, who does not fly, would not be able to climb up that tree to mate and lay eggs and they would be not webs to deal with.
Some people may suggest burning the webs out of trees but that is not a good idea and the heat from the burning will do more damage to the tree than the webs do.

Here is a link that might be useful: Fall Webworm

we call them bagworms ...

they are mostly irrelevant to any mature, otherwise healthy tree ... though ugly.. they rarely have any significant impact on the trees ... in my yard.. they are so far up in the cherry trees ... that short of spending hundreds of dollars to have professional sprayers come in ... there is nothing to do but ignore them ....

most wasp sprays are labeled for such .. you would wait until just before dark .. when they all return to the nest.. and shoot them ... making sure you are upwind ... you may not kill them all.. but you can reduce the population significantly ... and you will ONLY use sprays that are properly labeled.. now that you know what they are ....

that all said ... if i found a bag on a recent baby transplant ... i would act to help the babe.. but otherwise.. frankly .. its a waste of money and effort to deal with them on larger, more mature specimens ...

as with most bug onslaughts.. most years you barely notice them.. and every once in a while.. the populations seem to explode ... though you probably never noticed them .. as you drive around.. look for them. and you will see they are everywhere, this time of year .... you will NOT eradicate them.. and it wouldn't be worth the effort to try ...

good luck .. and be safe driving and looking in trees.. lol ...

ken

Kimmsr, where did you get the information that female webworms do not fly? You must be thinking of gypsy moths or some other species. ;-)

Neal, there are several predators and parasitoids that will help you get rid of these caterpillars and all you really need to do is to disrupt that protective web to make their job easier. You can attend to that with a strong spray of water, or a broom, etc. Any chemical application on your part will also affect the beneficials, and is not recommended for the control of this insect.

Though somewhat unsightly now, the leaves will regrow on that branch next year. Be sure to get rid of any remains of the webbing over the winter as there is some thought that the females are attracted to the same tree for that reason.

Thanks for the great tips and responses. I really appreciate them. I'm relieved that they probably won't damage the tree.

Now we have been getting lots of hard rain lately so I don't think that the water stream will be effective but I would rather the birds got them other than having to spray.

I'll try some of these techniques this w-end.

Thanks, Neal

Uhm.......bagworms are different than webworms or tent caterpillars. They build a small bag, a cocoony looking thing, in which the female spins a silk and lets herself down to an attachment point on some inanimate object. That's the one where the female doesn't fly around to mate, but the male comes to her in her mobile home. LOL. She doesn't not have wings, eyes or legs.

It's neat reading, and an unusual life cycle

Here is a link that might be useful: bagworms