Archive for Sunday, June 17, 2001

Treat early, before bagworm damage is done

June 17, 2001


Several insects can be quite damaging to the landscape. Few are more infamous than the dreaded bagworm.

These notorious insects primarily feed on evergreen trees and shrubs, but in heavy infestation years I have seen them hanging from street signs. If you have battled these pests in the past, there is a good chance that you will need to control them in the future.

Here are a few tips to help you win the war against the fearsome bagworm.

Bagworms overwinter as eggs inside the bags of last year's female worms. Young larvae normally hatch and emerge in mid- to late May in Lawrence. But this year I did not find larvae until the second week in June. However, reports from other parts of the state show normal hatches occurred around Memorial Day.

With such variation in hatch time, it is best if you check for live bagworms before spraying your landscape. Recently hatched bagworms are light green in color and are the same size and shape as a pencil lead. They grow rapidly and produce miniature versions of the adult bags.

If you spot young bagworms on evergreen trees and shrubs, start pesticide treatment now. There should be enough time for most of the worms to emerge, yet they will still be small and easy to kill.

A number of contact insecticides are labeled for bagworm control in the home landscape. Some of the more common chemicals are cyfluthrin, Orthene, Dursban, malathion and Sevin. If you prefer an organic control, choose products containing Bacillus thuringiensis. This natural toxin is effective if used on larvae while they are small.

The key to success with any of these products is to thoroughly cover the upper and lower leaf surface, as well as the branches and trunks of infested plants.

Bagworms have been around as long as we have been growing evergreen trees and shrubs in the landscape. With little known benefit to society, their claim to fame is the damage they cause by eating foliage from a variety of plants.

When it comes to controlling bagworms, the best line of defense is a good offense. Scout for the young larvae now. If found, treat with an approved insecticide. Then reinspect in seven to 10 days and treat again if needed.

Bruce Chladny is horticulture agent at K-State Research and Extension-Douglas County. For more information, call him at 843-7058 from 8 a.m. to 5 p.m. weekdays.

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