Bagworm Control

What are bagworms?

Bagworms are insects belonging to the family Psychidae, known for their unique habit of constructing protective cases made of silk and bits of plant material. These cases, resembling tiny bags or cones, serve as both shelter and camouflage for the larvae as they feed and grow. Bagworms are notorious for their voracious appetite, primarily targeting a wide range of trees and shrubs. As they mature, male bagworms develop into moth-like creatures capable of flight, while females remain within their bags, laying eggs to continue the life cycle.

When to spot bagworms?

Bagworms are easy to control when they are young and cause minimal damage to plants. Look for bagworms in late June. Use the Fourth of July as a reminder date. The bagworms will be very small at this time and are easy to stop with almost any product. They may be as small as a grain of rice, so look closely at them.

How to treat bagworms naturally?

Always the best plant care method is done with natural products. Horticultural oils and soaps, as well as BT and Bacillus thuringiensis, will work when they are small. These are sold under several names, such as Dipel. This natural control only attacks the caterpillar’s stomach lining, so it will stop feeding and die. Oils, soaps, and BT are the safest products to use since they are not harmful to people and pets.

When will natural treatments for bagworms no longer work?

As the bagworms grow, they develop a second stomach liner, and BT is not effective. At this phase, traditional pesticides need to be used. If the caterpillar is out of the bag and feeding, contact insecticidal sprays can be used. They are out of the bag feeding in the early morning or evening. During the day they often hide from the sun inside the bag. When spraying while the caterpillars are not feeding, a systemic insecticidal spray (one that is absorbed into the plant leaves) should be used.

When the bagworm starts feeding on the leaves, it will ingest the plant leaf that has been treated with the systemic insecticide and die. As the bagworm matures, it pupates and stays inside the bag until it emerges as a moth, lays eggs which hatch into the caterpillar and the cycle starts over again. Once the bagworm pupates, insecticides have no effect, and the bag must be removed from the plant manually. A week after spraying, check the bags on the trees to ensure the worm has dried up and is dead.