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Trees with brown bags attached to the twigs??…… .And then you say, pick these bags off by hand??….. You’ve got to be kidding!!….

It’s time to inspect your landscape for bagworm damage. Bagworms have become an increasing problem in our area of Nebraska. Though chemical control is not effective in the fall, manual effort pays great dividends.

Common bagworm larvae prefer cedar, blue spruce and arborvitae conifers, but other trees and shrubs are also prime feeding sources. As the larvae feed, they eat the bud of the conifers, causing branch dieback and open, dead areas. Plant death can result the following year due to defoliation of buds. Bagworm eggs actually hatched in late May or early June. As they hatch, the small blackish larvae crawl out of the bottom of last year’s bag and spin down on a strand of silk. When they are blown to, or find, a suitable host plant, the young larvae immediately begin to form a new bag over its body, usually less than 1/8 inch long, soon to be covered with sawdust like fecal pellets. Following a summer of feeding, larvae mature by mid August, when they move to a stronger branch to overwinter.

Why should I be concerned about bagworm control this Fall? The common bagworm is an interesting caterpillar. It is most commonly noticed when we see a spindle-shaped silk bag camouflaged with bits of foliage, bark and other debris. These bags can be from 1-1/2 to 2-1/2 inches long, making them more noticeable in the Fall. Within the bag is either a male or a female larvae (looks like a cutworm) that has been feeding on your trees. The female larvae, now containing between 500 and 1000 eggs, mummifies around the egg mass in its body. All remains quiet until next spring when the cycle repeats itself. Without a need to do additional feeding, chemical control of the bagworm is no longer effective until Spring. But, one can destroy the eggs at this time with the oldest insect prevention method known to man – hand picking. Remember to destroy the bagworms you pick by placing them in the trash. Dropping bagworms to the ground will not destroy the egg mass within the female worm. If one can destroy 1000 eggs by cutting off one bagworm, it’s a saving to both the tree and the pocketbook.

Your University of Nebraska Extension in Adams County has further information about bagworms. Remember, if the bagworms hang on the trees over the winter months, there will be more work to do in the spring when the eggs hatch. Chemical control is highly effective when applied properly after eggs hatch. My suggestion is to cut off all bagworms you can reach when the pickin’ is good.

About the author: Don Siffring

Don Siffring is a 6 year Master Gardener with the University of Nebraska Extension in Adams County. He is a professor emeritus with the University of NE, Institute of Agriculture. Don works part-time as a Horticulture Aide with UNL Extension in Adams County. Don and his wife, Bev, retired to the Hastings Community in in 2003 to be closer to their married daughter and husband, Christi and Brian Berns of Bladen.