When many small bagworms are infesting evergreens, an insecticide may be needed to prevent serious damage. In Kentucky, this is usually in June. Small larvae are more vulnerable to insecticides, and inflict less damage. Carefully inspect susceptible landscape plants, especially evergreens, for last year s bags. Preventive treatment is often justified on plants that were heavily infested with bagworms the previous year.
Several products are available for homeowner and professional use.
The BT products have very low mammalian toxicities, but are only effective against younger larvae. For nursery and landscape professionals, other effective products include Astro, Decathlon, Ficam, Mavrik, Orthene, Pounce, Scimitar, Talstar and Tempo. Foliage should be throughly wetted with the insecticide spray in order to achieve thorough coverage. Trade names are used as examples. No endorsement is intended, nor criticism implied of similar products not named.