Bagworms
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Bagworms occur throughout North Carolina. Bagworms have a very wide host range but are usually associated with arborvitae or juniper. A single bagworm does relatively little harm as it feeds on leaves. If the population builds up as it often does over a few years, excessive defoliation may kill conifers within one or two seasons. Damage is most noticeable in landscapes rather than woodlands. Occasionally, the silk band with which the bagworms attach themselves to a twig before they pupate girdles the twig as the twig enlarges. Winter is spent as eggs (500 to 1000) in the mother's bag.
Bagworms hatch in late May and June. The newly hatched larvae spin down on silken threads and are blown about by the spring breezes. Most of the larvae land on the original host plant but some small worms may be "ballooned" for a short distance on the silk thread. Upon reaching a suitable host, the worm begins to spin its bag and as it grows, it incorporates some of the host plant foliage into the bag for camouflage. As the bagworm grows, it enlarges the bag and adds fresh plant material to the outside. In August the worms mature and molt into the pupal stage. The bag is firmly attached by a sturdy silk band, which the bagworms usually wrap around a twig. During August and September, male moths emerge from their bags to mate. After mating, females lay their eggs inside the pupal cast skins and die.
Keep in mind that most often bagworms are found on needle leafed evergreens. However, they may also feed on any plant material they come across if their prefered food source has been destroyed or is not found. I have seen them do heavy damage to bald cypress, wax myrtle, willow oaks, crape myrtle, english ivy, and indian hawthorn.
Young bagworms that have not enclosed themselves in their bags can be controlled with products containing acephate (Orthene), Bacillus thuringiensis (Dipel), carbaryl (Sevin), bifenthrin, malathion, or spinosad. Two applications spaced at 7 to 10 days works well. When bagworms have already enclosed themselves in their bags, all we can do is remove them my hand and destroy them to prevent next years crop. No need to apply pesticides then. So if you have some plants that have a few old large bagworm bags on them, now is the time to be check for bagworms and treating if necessary.
If you have questions about your lawn, garden, trees, or landscapes give the Pitt County NC Cooperative Extension Master Gardener Volunteers a call at 902-1705. You can leave a message anytime to have your call returned. Volunteers staff the office on Monday, Wednesday, and Friday from 10 am to noon. Questions can be emailed to pittcomgv@hotmail.com
Danny Lauderdale, Extension Agent
Agriculture - Horticulture