Bagworms fill your tree with hard, brown bags that hang down like Christmas ornaments. Despite their innocent appearance, this insect wreaks havoc on the trees. They destroy the foliage, which is particularly harmful to evergreens since this often results in branch death. Using the correct products to spray on the trees is an effective way to control them.
Types of Spray
Spraying insecticides is a practical way to get rid of the bagworm infestation. Bacillus thuringiensis kurstaki, cyfluthrin, spinosad and trichlorfon are all proficient in controlling the bagworms. Acephate, malathion, carbaryl and permethrin products state they are helpful in controlling bagworms as well. The insecticides are available at garden centers and hardware and home supply stores. Follow the directions on the label for the best results for the product you choose.
When to Spray
Insecticide sprays are effective on young or more mature larvae. Chemical treatment is not as useful on bags 3/4 inch long or longer. The bacterium Bacillus thuringiensis works best on young caterpillars soon after they hatch in late May or June. Trichlorfon and cyfluthrin work well on larger larvae until early July. Spraying in late summer or early autumn is not as effective.
Saturation of the Foliage
Although the insecticides are expensive, it is important to saturate the trees well. Bacillus thuringiensis is effective when the young caterpillars ingest the insecticide, therefore, thorough saturation ensures the leaves are covered with the chemical. The same type of coverage is necessary for all other chemicals to provide adequate control and to rid the trees of the infestation.
Other Effective Control
Picking the bags off your tree by hand is an effective way to get rid of the pest in the autumn months through the middle of spring. Grasp the bag by the stem that allows it to hang from the tree. Tug sharply to release it and discard it in an outdoor trash receptacle in a sealed garbage bag. Steinernema carpocapse is a species of nematode that is effective in attacking female bagworms inside the bag. Use this treatment before the females lay eggs in the early fall.