While we haven’t seen a lot of bagworm activity yet, they are out there, and here’s what you need to know.

Most of us are familiar with bagworms having seen their bag-like home on a variety of plants and structures. For the most part, bagworms seem to prefer eastern red cedar, arborvitae, or other junipers. However, they can take up residence most anywhere, even on buildings.

Bagworm eggs overwinter inside the bags and begin to hatch sometime in April or early May. Once they hatch then exit the bag and begin to feed while constructing new bag/homes. Their bags are initially about 1/4 of an inch long, but they increase the size of the bag as they grow. When the larvae are fully grown, their bag/homes will be about 1.5 to 2 inches in length. Bagworms move around by poking their head out of the bag and carrying the bag around with them. Once mature, they permanently attach themselves to the host plant.

Pupation occurs within the bag with the adult males emerging in late summer to early fall. Adult male bagworms are small, black, hairy moths that have a wingspan of about an inch. Like most creatures, upon reaching adulthood, they begin their search for a female mating partner.

Females can be found inside of their bag/homes. Females, in contrast to the males, are wingless, and without functional legs, eyes, or antennae. They pretty much continue to look like larvae.

Once a female is located, the male enters the bag to mate where a fertilized female can lay between 500 and 1000 eggs. These eggs will overwinter inside the bag to hatch the following spring.

It’s somewhat problematic to attempt to control bagworms with pesticides since they spend most of their lives protected, inside their bags. However, you do have options.

The first option would be to remove the bags by hand and destroy them. Now would be the time to keep your eye out for those smaller size bags. This option is less appropriate for larger shrubs.

As far as a chemical control solution goes, we recommend an organic pesticide called bacillus thuringiensis, also known as bT. BT is a natural compound that is found in the soil that happens to be toxic to caterpillars. The caterpillars, eat the bT, become sick to their stomach, quit eating, and die. One of the good things about bT is that there isn’t any collateral damage to other insects, plus it is safe around humans and pets.

Timing your use of bT is however critical. You’ll need to spray the infested shrub while the bagworms are relatively small and feeding. That time is about now.

While bagworms don’t do a lot of damage unless they are present in large quantities, without effective control, their populations will increase over time to problematic levels. Good luck.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: Arnold T. Drooz, USDA Forest Service, Bugwood.org