Bagworms are a destructive pest which will target trees like evergreens. If given the chance, they’re numbers will grow until the damage they do will eventually lead to plant death.
Bagworms start anew each spring which is the best time to take control of the problem. If you saw bagworms the preceding fall, they will be back the following spring. So to knock them out, you’ll want to spray with BIFEN XTS treating the infected tree and surrounding landscape.
Stage your treatments to once a month and if you got them early enough, you won’t be seeing any that calendar year. But if its fall and you’re only now noticing them, be prepared to have them for at least another year.