How to Get Rid of Bagworm Moths

Published June 2, 2021

Bagworms are the larval stage of a moth. They can damage your trees and shrubs. Learn the ways to treat them, and let us know if you have any concerns.

At GreenPro we pride ourselves not just on our breadth of knowledge and wisdom about various issues related to landscapes and property design but also those specifically related to Oklahoma topography. This includes threats to your vegetation and greenery, including one specific to Oklahoma: bagworms, a constant threat for homeowners here.

Bagworms are caterpillars that make distinctive spindle-shape bags on trees and shrubs throughout the Tulsa area. They attack deciduous trees and evergreens but are especially damaging to juniper, arborvitae, spruce and cedar. Large populations of bagworms can defoliate many of your favorite landscape trees and shrubs, stripping plants of their foliage and eventually cause them to die. Infestations often go unnoticed because people mistake the protective bags for pinecones or other plant structures.

Bagworms are the larval (caterpillar) stage of a moth. Only the males develop into moths capable of flight. The adult female is grub-like and remains inside the bag until just before she dies. Bagworms pass the winter as eggs inside the bag that contained the previous year’s female. In mid- to late-May, the eggs hatch, and the tiny larvae crawl out from the end of the bag in search of food. There is one generation per year.

How To Get Rid of Bagworms

There are a couple of methods you can use to control bagworm populations on your property.

Natural control

If only a few small trees or shrubs are infested, picking bags off by hand and disposing of them may provide you a degree of satisfactory control. This approach is most effective in fall, winter, or early spring before the eggs hatch. When larvae become active, bagworms can still be removed by hand if the numbers are small and the affected host plants are small enough to reach the canopy.

Biological control

There are several naturally occurring parasitic wasps and predatory insects that attack bagworms. The activity of these natural enemies apparently explains the fluctuation in bagworm populations observed from year-to-year.

Chemical control

Chemical controls are most effective if applied early when larvae are small. In Oklahoma, it is normally a good practice to make applications of insecticide by early June. Bacillus thuringiensis var. kurstaki, a bacterial insecticide, is reported to provide good control of bagworms. Also effective are products that contain the active ingredient spinosad, another microbial agent.

The caterpillars must ingest these insecticides in order to achieve kill, so be patient as it will take some time to see results. Repeat applications may be needed later in the summer in order to keep susceptible plants free of bagworms. This is not due to the occurrence of multiple generations. Rather, not all eggs will hatch at the same time in some years and there may be migration of larvae between host plants.

In most years, treatment in early June will catch most of the emerging larvae and provide good, season-long control. The larger, older larvae can be controlled with products containing acephate (Orthene), carbaryl (Sevin), bifenthrin, cyfluthrin, and lambda-cyhalothrin.

Are you seeing the signs of bagworms around your property? At GreenPro we can help you figure out whether you’re dealing with bagworms and, if so, what the best course of treatment is.

Don’t let those bagworms bug you; give us a call today!