Hi--I have a shrub maple outside my window and have just seen that one portion of the tree is covered with (I guess) bagworms. What do I do about this? Whom should I call? It's a small tree--you can see a No Parking sign in its lower left branches--and only about 8' beyond my window. In Baltimore City, near Penn Station. Thanks for your advice!!
These are not bagworms. This looks like fall webworm. http://extension.umd.edu/hgic/fall-webworm-trees
There are predators and parasitoids that attack and kill fall webworm. You can open the webbing with a pole pruner and expose the contents to birds. The webworms rarely consume enough leaves to affect growth.
Ok, These guys have eaten all the leaves that are enclosed in their webs. You say they shouldn't affect growth; is that because there simply aren't that many webs?
This is a native insect. They don't tend to kill their host because they need the host to survive in order to feed on it another time.
Yes, webworms simply don't eat enough to do fatal damage to a tree (the exception would be a very young, small tree.) Also, trees produce more leaves than they need, for this very situation. They can afford to lose some.
If you can easily reach the nests, pulling them out by hand and dropping them in a bucket of soapy water is fast, easy, cheap and very satisfying.