Question
I have two cypress trees in my back yard and have discovered this hanging like cocoon that makes you think that it is part of the leaf coming out as it has the prickly little things on the outside of this cocoon type hanging thing.  I can tell that there is either a catipillar or a worm that will turn into a moth or something when I squeeze the end of it.  Can you tell me what it is & what do I treat my trees with & will it go to other trees or bushes that I have?
Thanks,
Becky

Answer
These are called bagworms. The common bagworm, Thyridopteryx ephemeraeformis (Haworth), is an interesting caterpillar. The most commonly observed form of this pest is the spindle-shaped silk bag camouflaged with bits of foliage, bark and other debris . Completed bags range from 1-1/2 to 2-1/2 inches long. The larva within the bag is brown or tan, mottled with black, and the bee-like adult males have clear wings and fur covered bodies. The females remain larva-like and do not emerge from the bag. The larva may stick its head and front legs out of the top of the bag to feed and move. When disturbed, the larva immediately pulls its head into the bag and holds the opening closed. Mature larvae may stay on their host plant or drag their bags some distance before firmly attaching the bag for transformation into the adult stage.

The bagworm occurs in the eastern United States from New England to Nebraska and south through Texas. The larvae seem to prefer arborvitae and red cedar but many other conifers and deciduous trees are attacked. These include: pine, spruce, cypress, juniper, willow, black locust, sycamore, apple, maple, elm, poplar, oak, and birch.

Mechanical control--If the trees are small enough to reach the foliage pick the bags off and destroy them.

Biological Control-Use the Bacterial Spray Bt The bacterium, Bacillus thuringiensis (Bt), is effective against bagworms if it is used against young larvae. Applications should be made at the end of June after all the eggs have hatched and the larvae are through ballooning.

Chemical Control-Insecticide Sprays Stomach insecticides are very useful for control of bagworms. Remember that the plant foliage is to be thoroughly covered because the larvae are protected from contact by being in the silk bag. Again, early sprays against young larvae are more effective than later applications. Products registered for bagworm control are: acephate (Orthene), bifenthrin (Talstar), carbaryl (Sevin), chlorpyrifos (Dursban),  diazinon, dimethoate (Cygon), malathion, nicotine sulfate, and pyrethrum.