While we aren’t seeing bagworms to the degree we have seen them in pas years, we know they are out there. Bagworms are the creatures that live inside those likely familiar little bag-like structures we find hanging out on some of our plants. And typically, inside those bags, there are small insects in their larval stage of life.

Bagworms go through 4 distinct stages of life: egg, larvae, pupae, adult. They overwinter as eggs in these familiar bags to hatch sometime in April or early May. Since there can be 500 to 1000 eggs in a single bag, they are not doubt anxious to move out to create their own living quarters. When they exit, they begin to feed on the plant on which they are located and construct their own bag. For the females, just about their entire life is spent inside of a bag, while the males exit the bag as an adult to of course, search for a female.

Initially these bags are only about a quarter of an inch in length, but as they eat and grow, they enlarge the size of their unique homes. Ultimately, these bags will end up being an inch and a half to two inches in length. They move by poking their head out and pulling themselves along…bag attached. When they have reached the end of their larval stage, they attach themselves permanently to a branch and begin to pupate within the bag.

Somewhere around the end of summer, male bagworms emerge as small, black, hairy moths with a wingspan of about an inch. At this point the begin their search for a female. Females never leave the bag. They are wingless and without any sort of functional legs to move them about. They also don’t have eyes or antennae. For the most part, they continue to look like larvae.

Fertilized females will then lay their eggs within the bag which is where they stay over the winter. In the spring they will hatch, and the process begins again.

Bagworms seem to prefer arborvitae, eastern red cedar, and other junipers. However, they can take up residence most anywhere, even attaching themselves to the sides of buildings is not unusual.

Control of these insects can be a bit problematic. Your first and probably best option is to remove the bags by hand and dispose of them. However, this can be a problem on larger trees and shrubs since we likely won’t be able to get where we need to be to remove them all.

We have a pretty good organic solution in a product called bacillus thuringiensis, also known as bT. BT is a natural compound found in the soil that happens to be toxic to caterpillars. When bagworms eat something treated with bT, they lose their appetite and quite eating. One of the good things about bT is that it is only effective on caterpillars so there won’t be any collateral damage from the use of bT.

For bT to be effective, your timing is critical. You need to spray the plants when the bags are relatively small and feeding. If they are not in feeding mode, they are well protected inside of those bags and safe from pesticides.

While it’s true that bagworm damage isn’t particularly harmful, it can be if you have them in large quantities. So, you’ll want to try and get them under control before their numbers build up over time. 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: Tom Ingram