Check and Double-Check for Bagworms

Whether you’re a novice or an old pro at finding bagworms be sure and check your trees and shrubs now for this pest.  They can do considerable damage and even kill numerous plants in the landscape buy they are especially fond of junipers, arborvitae and spruce trees.  They can also be found on black locust, maple and sycamore trees.  If you haven’t checked for bagworms you should and if you have checked you should do a double check for them.

The bagworm is a native moth and is thought to feed on 128 different plant species.  Last season they seemed to be in high numbers and they are showing up in all parts of Northwest Missouri this summer.  I’ve observed active bagworms from Buchanan County area to counties along the Iowa border.  The cooler wet conditions this spring may have slowed them down some.  We generally recommend controlling them while they are young, before they get 3/4 to an inch long.  Although we nearly past the recommended time for spraying, the bagworms I’ve seen are still small so treating for them should be successful.

Some bagworm facts:

• The bagworm is a native plant pest that can be found feeding on plants in the landscape, especially coniferous (needled evergreen) plants.
• They generally start hatching the end of May to the first part of June and eggs will continue to hatch for 2-3 weeks or more.
• The young larvae (worm) starts forming a silk bag around its body as it starts feeding on the host plant.  The females will remain in this bag their whole life.  A male will pupate and emerge from the bag as a clear wing moth to mate with the female around mid September.
• After mating a female will lay from 500-1,000 eggs in the bag.  The eggs overwinter in the bag and will hatch the following spring (around the 1st part of June).
• They can hatch for a period of 2 to 3 weeks until about mid June in most years.  There is 1 generation per year.
• They should be controlled after hatching is complete and while they are still young (less than an inch long).

Some species of bird such as the sapsucker and woodpeckers will feed on bagworms as will some insect predators.  You can also pick bagworms off the plant and destroy them by placing the bags in some soapy water.  If this is not feasible there are several materials that can be used for control.  Materials labeled for bagworm control should be affective.  The key for control is to spray when the worms are small and to get good coverage on the plant on the inside and outer edges of the plant.

The ingredients of some of the insecticides labeled for control include:  Bacillus thuringiensis (Dipel), this is a natural material that will make the worms sick and die, good coverage when they are small is essential, Cyfluthrin (Tempo), Acephate (Orthene), Spinosad (Conserve), Carbaryl (Sevin) and Trichlorfon (Dylox) are a few of the insectides available.  The word in the ( ) is a trade name.  There are many other trade names available, these are just a few examples.  Be sure to check the product label and find bagworm on the insects controlled list and follow the directions for mixing and application.

Bagworms will congregate in the top of the tree but they can be found throughout the plant.  Thorough coverage of the plant is important for bagworm control.  The spray material will need to be directed to the inner and outer portions of the plant.  A spray just on the outer perimeter of the plant will not be very effective.  You may want to consider hiring a professional for plantings with dense foliage and/or tall plants.

For more information contact your county MU Extension office and ask for guide G7250, The Bagworm in Missouri.  You can also go to the MU Extension online at http://extension.missouri.edu and search for the guide.  Information for this article was obtained from MU and K-State Extension
Entomologists.

Taken from the Northwest Missouri Extension News.  Written by Tom Fowler, Horticulture Specialist