Not quite…Lately, we noticed that one out of our seven Thuja Green Giant Arborvitaes was beginning to turn brown. We simply could not figure out why only one of the seven would be dying. The rest looked 100% healthy. However, after calling around to a few local nurseries, we discovered the reason. As most of you know evergreens or conifers typically have cones. I thought this was the case with the Thuja trees that we planted two years ago in my yard as well. However, I was extremely mistaken. Instead of my evergreen having cones, it has bagworms. That’s right worms! The cone-like objects hanging in my tree for the past months were in fact a colony of plant destroying larva.
So what is a bagworm, and why does it look like that? The bagworm is a form of caterpillar that spins silk and combines it with the materials from mostly evergreen trees and shrubs, creating a cocoon. Because it uses large materials from the plant, it doesn’t look like the traditional cocoons of most caterpillars. Instead, it resembles the shape and material of a cone. This of course benefits the worm, but makes it very difficult to for predators, including humans who do not want their trees to die, to find or see them. After feeding on the tree, and suffocating its branches from the tightly spun silk, the bagworms will eventually turn into a type of moth, as the tree dies. The entire life process takes one year.
So, how big are the bagworms or cocoons? They range from about 1/4th of an inch to 2″ long, as you can see in the photos that I took above. And lastly, what are we going to do with them? I plucked them off my tree. That’s right I stood around my tree for about three hours today, plucking and cutting at least two hundred cocoons. Jennifer did help me get started. Then I placed them in a bucket, and drowned them with water. Later this week, I will continue to destroy them by spraying any remaining larva, cocoons, or eggs on the tree with an insecticide.
Although I had to spend a portion of my Saturday afternoon removing many cocoons from my tree that may still die, I now have a cool adaptation that I can share with my science class next year.
Jason
