Bagworms Need to Be Picked and Sprayed Right Now

First posted on 09-05-2008

The bagworm is a real nuisance pest that can cause considerable damage to some plants according to Pat Byers, horticulture specialist, University of Missouri Extension.

“The most noticeable sign of a bagworm infestation is the presence of silken bags attached to a branch. The bag resembles a Christmas tree ornament hanging from a limb,” said Byers.

Two types of control are generally effective: chemical applications and hand picking.

The safest and least expensive method of controlling bagworms on small trees and ornamentals is to hand-pick the bags. But how practical it is to hand pick the bags from the trees (or shrubs) may depend on bagworm numbers and plant size.

From late May to mid-June, bagworm caterpillars begin emerging from the bags.

“Watch your susceptible plants closely for the young larvae. This is the very best time for chemical sprays to be most effective,” said Byers.

Chemical control becomes less effective as the season progresses because of the increased size of the larva according to Byers.

Common chemicals effective are carbaryl (Sevin), malathion, acephate (Orthene) and Bacillus thuringiensis (Bt).

By mid-September the bagworm has completed its development. The adult female bagworm lays between 500 and 1000 eggs within her bag, after which she dies. The eggs remain within the bag throughout the winter until they hatch the following spring.

For more information, or answers to your specific lawn and garden questions, contact Byers or the Greene County Master Gardener Hotline at (417) 862-9284.

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