Bagworms grow quickly on trees, shrubs

A gardening colleague once told me that now was the best time to treat for bagworms.

I asked him what made him think of that. His response was because the Catalpa trees are in bloom. Some gardeners garden according to the moon while others garden by observing indicator plants. As it turns out, Catalpa trees are a good indicator of the emergence of bagworms.

Bagworms are a serious problem on evergreen trees and shrubs. Although they begin small, they grow quickly and have a large appetite that can eat a shrub to the ground. If you had bagworms last year, there was a good chance you will have them again this year.

Here are tips to help keep your landscape safe from these destructive insects:

Bagworms are a perennial problem in our area. They overwinter as eggs inside the bags of last year’s female worms. In the spring, the eggs hatch to begin the cycle again. The newly hatched bagworms are less than 1/16 of an inch long and are light green in color. They grow rapidly and produce miniature versions of the adult bags within a few days.

Spend a few minutes inspecting your evergreen trees and shrubs this weekend. Look for tiny bagworm larvae crawling around carrying their “home.” Begin treatment if you spot them. By now, all the worms should have emerged, yet they are still small enough to be controlled easily. The longer you wait, the more damage they will cause and the more difficult they will be to control. A number of insecticides are labeled for bagworm control in the home landscape.

Some of the more common chemicals are cyfluthrin, Orthene, malathion and Sevin. If you are interested in using 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 both the upper and lower leaf surface, as well as all the branches and trunks of infested plants.

— 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.