Bagworms

Bagworms feed on the leaves of evergreens such as white pine, blue spruce, and red cedar. They can also be found on deciduous trees such as cypress. As bagworm caterpillars mature they hang like ornaments. Damage is most severe on evergreens where leaf loss can cause branch death. The trouble is often we don't notice the bags and the damage until late in the season when hand picking the bags is the only option.

The female bagworm is eyeless, without wings, legs or antennae or functional mouthparts. She has a soft yellowish white, almost hairless body and stays in the bag. She never leaves the bag. The male moth is black and almost clear winged. The mail moth emerges from his bag in late summer, flies to the female, mates and dies in a few days.

The female produces 500 –1000 eggs in one bag, which can mean large populations on a single plant. They spend the winter as eggs in the bag.

The bag is made of silk and bits of twigs and leaves of the host plant. Active bags will have green leaves or needles on the top. The bag enlarges as the caterpillar grows.

In southern Illinois bagworm egg hatch occurs in June. Pesticides are most effective if applied two weeks after egg hatch. Control should begin in mid June. An additional application is advised one to two weeks later to control later emerging caterpillars.

U of I Extension entomologist, recommend the following pesticides for controlling bagworms; Bacillus thuringiensis kurstaki (sold as Dipel or Thuricide), and insecticides with cyfluthin. Insecticide sprays are effective against the young larvae but bags that are ¾ in long or longer are very difficult to control. The bacterium Bacillus thuringiensis is effective on young caterpillars, but the material must be ingested—so thorough plant coverage is essential. Cyfluthrin is recommended for larger larvae, but again thorough cover is essential.

Mark your calendar now to eliminate the brown ornament bag soon to appear on your trees.