If you have noticed small, diamond-shaped silk bags or a mass of webbing at the end of your pecan tree's branches, there may be an infestation of bagworms or webworms. Bagworms are often found on arborvitae, but make webs on an array of trees, shrubs and ornamentals. Webworms are sometimes mistaken for bagworms and are often found on pecan trees. Bagworms and webworms both create silk bags, which are filled with many, tiny caterpillars. Treatment is the same for each, which involves removing the bags before the population multiplies and damages the tree.
Spray the tree with an insecticide made to kill caterpillars before the bags reach 1 to 2 inches long. Spray the insecticide late in the afternoon when there is no breeze. Some products are sensitive to the sun and may degrade in the sunlight.
Clip all noticeable bags off of the tree limbs with pruning shears. Place them in a sealed bag and discard them. Remove them as often as needed in fall, winter or early spring, before the eggs have hatched.
Pierce holes in the bags and pull down as much webbing as you can with a stick or pole. Discard the webbing. This exposes the bugs to birds and wasps, which are their natural enemies.
Place a jet-spray nozzle on your garden hose and spray webbed bags that are out of your reach. The strong jet of water may help knock them down or break a hole in them. Gather the webbed bags from the ground; place them in a sealed bag and dispose of them.
Place a bird feeder near the tree and fill it with bird seed to attract birds to the area. The birds will eat the bugs if they are exposed. The birds may tear open any missed bags and feed on the larvae.
Treat the tree again with an insecticide, if needed. Follow the manufacturer's instructions as to how often you should spray the tree.