The term Bagworm can mean different things to people so let’s figure out which one you have. If it lives inside webbing like a spider web with 100’s of worms inside the web it is really a Tent Caterpillar. If it carries its home with it individually then it is a Bagworm.
If you are seeing what looks almost like Christmas ornaments hanging on some of your landscape plants you have bagworms for sure. Bagworms hatch in early June and float on silk like strings in the wind to disperse. Each worm carries its home along with it as it moves from plant to plant. Its cocoon is made up of the same material the bagworm is feeding on so the Bagworm can be hard to see. Bagworms are a common problem in the area and are usually first noticed in mid to late July when they have grown to an inch or more long. Sometimes you notice that your evergreens are not looking good, kind of thin in appearance due to the feeding of the Bagworms. It is important to start control measures quickly, Bagworms can kill a tree. Bagworms seem to prefer evergreen plants like junipers or spruce but I have seen them working on all types of plants.
Control is not so difficult but you need to do a complete spray of your plants as the bagworms work all over the plant therefore good thorough penetration of the foliage with your insecticide is important.
There are some products available that are considered natural or Biorational that help control bagworms. Biorational insect controls kill worms while not controlling good insects that control mites and scale insects. BT or Dipel are both Bacillus thuringiensis. This product works especially well on young bagworms that are an inch or less long. Spinosad is another Biorational found in products like Fertilome Borer, Bagworm and Tent Caterpillar spray. Spinosad works well throughout the season.
Malathion is an old standby insect control as well as Ortho Orthene. Both offer good control on older, more mature Bagworms.
If you have discovered Bagworms this summer you will need to control them now and plan to spray next year as well. Missing one mature female bagworm that has up to 1000 eggs in her bag is all it takes to have an infestation next year. Start watching next spring in early June, about the time Catalpa trees bloom, Bagworms start hatching then. By starting early in your control it will be much easier to eliminate this insect pest.