By Mary Ann Carson
For The Independent

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Bagworm infestations, according to the Ohio State University Extension, may be found "from New England to Nebraska, and south through Texas." Bagworm larvae seem to show a preference for red cedar trees and arborvitae, but also feed on pine, spruce, cypress, juniper, willow, black locust, sycamore, apple, maple, elm poplar, oak and birch. Its scientific name is thyrirlopteryx ephemeraeformis.

In the past, bagworm invasions have been primarily a problem for the eastern United States. Now, these caterpillar-like worms are marching west. Jim Hruskoci, a UNL Extension Horticulturist at the Hall County Extension office, said the bagworms are new to this area.

He said the first time he encountered bagworms was about five years ago.

"A person from the Hall County Courthouse called with a question about their juniper bushes. They thought the bushes were forming seedpods. Upon inspection, they turned out to be the first bagworms I had seen in Hall County. I thought this might be an isolated incident, but the problem has become more and more insidious," Hruskoci said.

Tom Ummel, owner of Tom's Tree Service, of Grand Island, agreed that this is a recent problem.

"Bagworms haven't been a problem in this area until recent years," said Ummel, who has been in the tree business since he was 18. "In the last two years, I've really seen an increase in infestations especially in pines and cedars although they will attack any species if they are hungry enough."

Ohio State University Extension states that bagworms create a "single generation per year," and spend the winter as eggs inside the female bag, with as many as "300 to 1000 eggs in a bag." The eggs hatch in late May or early June as tiny black larvae with some males and some females. The larvae crawl out of the bottom of the bag and "spin down on a strand of silk." These, lightweight "larvae on a string" can be blown by the wind and "ballooned" to nearby plants.

As the young worms feed, they secrete silk and form a bag over their bodies, Hruskoci said.

"Bits of plant tissue become enmeshed in the bag as the worm feeds," he said, "and as it grows the bag enlarges to approximately 5 centimeters when complete. In August the worms mature and attach this bag to a sturdy branch with a band of silk, and pupate (change from a larval stage to an adult form)."

In August and September, Hruskoci continued, the male moths emerge from the bag complete with clear wings and fur covered bodies, to mate and live only one to two days. The females stay in a larva-like state, do not emerge from the bag and mummify around the egg mass in their bags until spring, when the cycle begins again.

Damage can rapidly develop, reports Ohio State University Extension, as female bagworms don't fly and areas crowded with larvae may suffer excessive defoliation. This may cause the entire plant to die the following season.

The most severe damage noted in Hall County, thus far, is southwest of Grand Island, Hruskoci said. One of the affected landowners, Bill Carson, first noted the bagworms last year.

"Last fall we noticed that the cedar trees in our pasture were dying," he said "We contacted Jim Hruskoci, at the Hall County Extension, and after examination he said that it was the worst case of bagworm infestation he had seen in the area. At least 16 of our mature cedars were bare except for the pod-like, bagworms hanging from the branches."

The solution

There are several ways to control bagworms.

"If you have only a few bags on your trees," Hruskoci said, "remove the bags from the trees and crush or burn them. Do not just put them in a compost pile, where they will be a ticking time bomb. They might crawl out or be blown by the wind to a host plant nearby. Also, cut the silk band that holds the bag on the tree, as it does not decay quickly, and can act as a tourniquet and may cause the branch to die."

If the infestation is more than just a handful of bags, chemical control with an insecticide spray is one of the most efficient controls.

"It won't do any good to spray your trees, until the bagworm eggs are hatched in the spring and crawling on the branches," Ummel said. "This can happen from late April to June. The whole tree needs to be sprayed, actually, soaked from the top, down. Then check the trees in 30 to 60 days to see if you still have any live larvae crawling on your trees. An additional spray may be necessary."

Hruskoci added there are some biological controls for bagworms, such as the use of the bacterial spray Bacillus thuringiensis (BT), against young larvae. BT is effective if used after the eggs have hatched and the larvae are actually crawling on the branches and feeding. It is safe for humans.

Another environmentally friendly control is the use of ichneumonid and chalcid wasps that parasitize the bagworm by laying their eggs inside their pupa, Hruskoci said. These wasps are safe to have around as they don't have stingers. One way to attract these wasps to your area is to plant flowering plants such as asters and Shasta daisies near trees susceptible to bagworm infestations.

Hruskoci and Ummel agree bagworm infestations are on the increase in the area, but they feel the damage can be controlled. Just remember, when applying chemical sprays to your property to eliminate bagworms, get professional help.

"Be sure to employ a certified sprayer," Ummel cautions. "These are people who have gone to school and learned how to use chemical sprays, safely in your environment and around your family."

"We don't want to alarm the public," Hruskoci said. "We just want homeowners to be aware of the bagworm infestations, so that they can take control now, and save their trees. We don't think this problem will go away anytime soon."