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From the 1997 Voice of the Forest
More than you ever wanted to know about bagworms-
Imagine a day in life of The Heart Forest!
The trees vibrating with feeding bagworms.
Yes, it’s true. The Heart Forest has a bit of nature we human caretakers would really rather have done without...Thyridopteryx ephemeraeformis (Haworth), or what we have come to call our Bag Ladies, and described as the most important species of bagworms in the U.S. by Bruce A. Barnett, MU Department of Entomology (only the best for us!)
Last year about 60% of the red cedars in the center of the Heart were damaged. We won’t know how severely injured the trees are until this spring when new growth begins. Locations where the cedars do not survive will be replanted in the fall.
The Heart Forest was not alone with this problem. Bagworms were more numerous all over the Kansas City region. This native moth is found extensively throughout the eastern and southern states and reportedly feeds on 128 plant species which includes red cedar and other juniper species, black locust, maple and sycamore.
The beginnings of the infestation were noticed about four years ago. The most obvious sign of bagworms is the presence of silken bags attached to a branch. In late May to mid-June the bagworm larvae, 500 to 1000 per bag, emerge and begin to make its own bag where it spends its entire life.
When a host plant becomes defoliated the larvae, with bag, will crawl off to find a new plant. Thankfully this method of colonization is slow because just a few species of birds (sapsuckers and woodpeckers) are able to tear open the tough pouches and insect predators and parasitoids can only control small populations. We are assuming the bagworms came with the cedars at the first planting in 1990 rather than walked to our isolated stand of trees.
The cheapest method of controlling bagworms on small trees is to handpick the bags and destroy the contents. Two years ago over 16 pounds of bagworms were removed and we followed-up with an organic bacterial spray. These methods proved to be ineffective as the trees got taller since the females who go to the topmost branches. This year a late summer chemical application from the ground proved to be too little, too late.
Despite how unsightly the trees look, samples of branches taken in December showed signs of life and the trees may bounce back.