The more common types of affected trees include junipers, cedars and bald cypress. This year I have seen them on more unusual species like Burr Oak, Live Oak, Japanese Maple and Crape Myrtle. In fact, the Burr Oak variety is very difficult to spot due to the materials attached.
The best way to treat them is when they are actively feeding on the leaves and before they have moved to their next stage of development - the pupae. They can be controlled by a number of chemicals or an organic treatment know as BT, which is a bacteria that once ingested by the caterpillar, will cause them to die.
For most bag worms now (June/July) is the "window of time" to apply a treatment. If your infestation appears to be causing defoliation of your trees and shrubs, have Heritage Tree Service of Texas take care of the problem for you.