Hello- Thank you for your invaluable service! I have bagworms that return every year. This year they showed up later than usual. I only sprayed with Bt last week. One article I saved, mentioned spraying with Spinosad after mid-July. Should that be my next application or continue with Bt? Also, should I spray weekly or less frequently. Thank you so much. I have used your service multiple times.
You are welcome and we are happy to have you back.
People sometimes confuse bagworms and our native fall webworms, which are also happening now in large numbers.
Here is our page on bagworms: https://www.extension.umd.edu/hgic/topics/bagworms-trees-and-shrubs
Bt only works on small caterpillars, that is, when they are not easy to see and their bags are small. It is likely too late for that to work.
How large is your tree?
Hand-picking the bags and throwing them in the trash is the easiest control.
It may be too late for further applications as they pupate in August/Sept. and the bags are thick.
Pull off all you can find and start early next June monitoring for the small ones to hit with Bt.
Hello again- Thanks for your very prompt response. These are definitely bagworms and they are on a long row of mature junipers. There are too many to pick. I actually started but got too frustrated. It sounds like I'm out of luck. So I should not bother with either Bt or Spinosad, correct? I'm mad at myself for not spraying earlier. In the past, I have started with Bt in late June and continued through the beginning of August. Would you happen to have any other suggestions (other than hand-picking)? Thanks again, Patti
Since bagworms are getting ready to pupate, sprays are not going to be effective on them now -- it's too late. The best thing to do at this time of year is hand-pick the bags. Then monitor for caterpillar activity early next summer and you can use Bt on the small caterpillars.