Remove all dirt, debris and insect matter from your home with the hose of a vacuum cleaner. To control the current infestation, remove any plaster bagworms or their larvae's watermelon-seed-shaped casings. Remove any spiderwebs, dust, hair, lint, dead insects and other matter to get rid of plaster bagworm feeding sites. Concentrate on areas adjacent to the stucco, on baseboards, moldings, under furniture and in any other cracks or crevices where debris likes to hide.
Wipe the stucco down with a well-wrung sponge and an enzyme cleaner diluted (if necessary) according to the label's instructions. Don't forget the baseboards and corners where dirt often accumulates.
Reduce the humidity in the area. Bagworms only feed on stucco when the weather is humid and there is ample moisture. Run the air conditioning or place a dehumidifier in the room to prevent further infestation.