Evergreen Bagworm

The Evergreen Bagworm is a pest found in almost all of the US, as far west as Nebraska, North to New England, and South to the Gulf of Mexico. Although it's called the Evergreen Bagworm, it doesn't necessarily attack only evergreens. It attacks cypress, pine, juniper, spruce, locust, birch, black locust, apple, oak, willow, sycamore, poplar, maple, and several other species of plants and trees. Red Cedar and Arborvitae are their favorite food, and are attacked most often. In my career I've seen them on just about everything, from a metal stop sign to a plastic eves trough. They can wiggle themselves anywhere, but they only feed on plant material.

They start life out as a black larva, growing brown and tan as they mature. Inside the mothers empty sac from the previous season, up to 1000 eggs can be hatched. They hatch between early April and June, depending on the weather and the temperatures. When they hatch, they drop down from the mothers sac on a small piece of silk string, which usually gets caught by the wind, carrying the larvae to their host tree. Once they reach their new host, they immediately start forming their own case to live in, feeding off the tree and using its leaves to build its sac. It wraps its' silk around the branches of the tree, sometimes so tightly that it can hurt the tree just from the squeeze.

These are some pictures of bagworms that I found just today. They were on an arborvitae.

Adult males come out of their sac around late August, and look like a black moth with a 1 inch wingspan. The females, however, never leave their sac. They die in it, surrounded by the eggs that will be hatched in the next season.

The sac that you may see hanging off of your trees is made of silk, fecal matter, and pieces of the tree that the Bagworm is latched onto. Often times that sac is hard to spot to the untrained eye. Especially on spruces, they look just like pine cones and blend in very well. The camouflage tactics that the Bagworm uses is very effective in keeping away predators.





Ways to stop Bagworms from destroying your trees: 
If you find that you have bagworms, one of the simple solutions is to simply pull them off the braches you find them on. It's best to do this right before spring, as the female is already dead and the eggs haven't hatched yet. Make sure to throw them away in a sealed container, so that the hatching eggs have nowhere to go. Another option: fire. Burn the sacs as you pick them off.

The chemical solution is insecticides, and they should be sprayed mid to late June. Bagworm feeding slows in August, which means insecticides won't be as effective during late summer/fall. Make sure to cover the entire tree with the insecticides because you usually will not be able to see all of them. New larva are very small and hard to spot.