Early June is the best time to control bagworms

By

Lala A. Kumar

Horticulture Specialist

University of Missouri Extension

Early June is the best time to control bagworms in Kansas City area. The bagworm can be a constant threat to many green and deciduous shrubs used for landscaping in the Kansas City area.The most commonly attackedhost plants are arborvitae, cedar and other juniper species,black locust, maple, and sycamore.

The most noticeable sign of a bag worm infestation is the presence of spindle-shaped silken bags attached to a branch. The bag some what resembles a Christmas tree ornament hanging from a branch. Bagworm larvae generally start emerging from theiroverwintering bags during the first part of June. Almostimmediately after emergence, a larva starts to produce its ownprotective bag or case around its body. With its head and legsfree, the larva is able to move about the plant as it feeds onthe foliage. As the larva grows, it increases the size of itsbag and incorporates into it bits of twigs and leaves forstrength and camouflage protection. Attacked plants are usuallypartially defoliated and weakened and rendered unsightly;however, it is not uncommon for complete defoliation to occur.For more information on bagworm and its life cycle visit our web site: or call the University of Missouri Master Gardener hot line on 816 -833-8733.

The cheapest method of controlling the bagworm on smalltrees and ornamentals is to hand-pick the bags in late fall or early spring reduces later infestation. Be sure to pickoff all the bags on the plant and destroy them. For largerplants where hand-picking is not practical, the bagworm can becontrolled chemically. Apply the insecticide as soon as thesmall larvae begin emerging from the overwintering bag in early June. Sprayapplications are most effective if made during this time. Chemical control becomes less effective as the season progressesbecause of the increased size of the larva and its bag. Thefollowing are some of the insecticides that can be used againstthe bagworm: Bacillus thuringiensis (Bt), Spinosad, Malathion, Acephate (Orthene) and Carbaryl (Sevin). Be sureto follow label directions and rates.

Note: Photo of Bagworm. Source: MU Extension