Bagworm
Feeding damage can be severe enough to kill the plants. Initially the bags are green but as the season progresses, the bags turn "brownish". As the larvae grow they enlarge the bags and feed on the entire leaf leaving only the veins. Eventually, the larvae pupate in the bag.
An ichneumon wasp is a natural predator. However, the bagworm usually causes serious damage before the wasp can control very many bagworms. Bacillus thuringensis kurstaki is a bacterial disease on caterpillars including bagworms. Bacillus thuringensis kurstaki can be bought at many stores selling insecticides for the home landscape. When the commercial product is applied while the bagworm is still a larva, the bacterium can be very effective. Contact your local Extension Service for the proper timing in your area.
James E. Schuster, retired Extension Specialist, Horticulture & Plant Pathology and Dr. Philip L. Nixon, Extension Entomologist, Dept. of Crop Sciences, University of Illinois