All About Bagworms

What are bagworms?

Bagworms are tiny little caterpillars that turn into moths. They feed on trees such as Junipers, red cedar’s, arborvitae, Leyland Cypress, and other evergreen type trees. Sometimes you will see them in random spots such as the bottom of a fire hydrant or on a species of tree that you wouldn’t expect, but it is likely the female just moved their bag their when it laid its eggs.

Are bagworms harmful?

They can be. The trees that are usually attacked are generally smaller and don’t store as much energy which means they get their energy from constant photosynthesis. When a bagworm infestation comes along and defoliates an entire tree, the tree is at risk of dying. But if it’s a light infestation, you may just wait until next year to treat it and start saving your pennies. If the tree loses a few leaves it’s not a big deal. The question is, do you have a procrastinators personality?

Life cycle

Eggs are laid in a bag, the egg hatches and a caterpillar emerges! Sort of. The head and legs come out but the rest of it stays inside the bag so it can create a new bag by feeding on your tree. Once the bag is formed, it goes into its Pupal stage. The Female stays in her bag her entire life! When the adult male emerges from its bag, it mates with the females that are still in their bags, and dies within 2 days. The female lays its eggs in the bag and either becomes a mummy in the bag or falls out and dies. This whole cycle takes 1 year.

How to treat bagworms

Treatment needs to happen in late spring to early summer. In North Texas this happens around late May to mid-June. As long as you can see them moving on your tree, they haven’t sealed their bag and can still be hit by insecticide. Tree shepherds will spray a product called Bacillus Thuringienses (BT) to kill them. In the spraying process, we also knock a bunch of them off with a high-pressure spray gun. The other treatment is to handpick each one of them off. Talk about tedious!

What’s it cost to treat bagworms?

The cost depends on the size of the tree, but ranges from $80 – $145 for one tree. If you have multiple trees infested, there would likely be a multi-tree discount!

Check out this 3 second video on what they look like when they’re moving around!

Give us a call or email us if you have questions or want us to treat your tree!

Scott Geer

Scott Geer

Scott Geer has a master's degree in forestry from Stephen F. Austin State University and is an ISA Board Certified Master Arborist.® He is also a graduate of the American Society of Consulting Arborists Academy.