Tent caterpillars and bagworms tend to start showing up in summer and keep coming until fall. Early on they will form an infestation like the one shown below. Later you will see silky encasings either across your tree or hanging in a bag. These can be a problem for your pecan trees. You can also find these worms on a number of other trees and shrubs. If you notice a large mass of caterpillars or bagworms, treat them before they have a chance to move up your tree to harder to reach places. Some options for treatment are BT, carbaryl, or Malathion. Read the label before using any pesticide to make sure your variety of tree is listed.
If you are noticing caterpillars and bagworms later on in their life cycle, you should get a hold of a tree care professional. Pressurized spray equipment is usually needed to reach high locations on the tree. Large worm bags need to be removed from the tree completely. If you are set on doing it yourself, try to remove as many bags as you can and throw them away in a sealed bag. If you can't quite remove higher bags, damage them or at least puncture them. Put a bird feeder near the base of the tree to attract birds. The birds will not kill all of the caterpillars, but they will knock down the population some.
If you are in Baton Rouge, New Orleans, or somewhere in Louisiana between, contact Big Bark Tree Care to take care of your trees.