SFgate - Homeguides has shared tips on h0w to kill bagworms. See them below:
Remove the bags from the tree by hand picking them or knocking them from higher branches with a pole. Place the bagworm bags in sturdy plastic bags, seal them securely and dispose of them.
Spray the tree with insecticide labeled for use against bagworms in mid to late spring. Watch for the young worms so you can spray soon after they emerge from the bags. Use insecticides containing Bacillus thuringiensis (Bt) two or three times at seven- to 10-day intervals.
See a list of pesticides that have shown to be most effective on young bagworms on small trees at Purdue University. Read the entire label before using an insecticide, and follow the instructions for mixing and applying the product exactly. Store unused portions in the original container and out of the reach of children and pets.
- Hang pheromone traps in cedar trees in late summer when male bagworms are in search of bags containing females. The traps catch the males and interrupt the bagworm life cycle. Pheromone traps don't provide complete control. Use them in conjunction with other control measures.
Trees in Windsor, Canada could soon be under attack! The bagworm has made a return. Read more at CBC.ca.