We usually don’t notice bagworms until they start to look like this. When bagworms get to this size, there isn’t much you can do besides pick them off. If you can pay attention to your trees, and your plants, and control them earlier in the season, you’ll have a better chance of stopping them from feeding on your shrubs and trees, and killing them.
The males will turn into a fly that emerges from the bag late in August. The males will come to the female bags, and mate with the females. And then the females lay eggs inside the bag. They can lay four or five hundred eggs in one single bag. So, each one of these will turn into quite a few more bagworms.
Then, these bags will stay on the tree all winter. In early mid-May to late June, all of those babies will be hatching out of the bags, and they’ll begin feeding on the tree. You won’t notice them unless you’re looking for them because they’re so small.
You can look at a variety of insecticides. There are some pesticides that are considered safer – such as bacillus thuringiensis, and spinosad. They’re typically more effective on small insects, so you may have to make two or three applications. It’s important to get the entire tree covered, in order to control all of them. Make sure that you get the spray deep inside of the tree, and not just out on the surface.
If you’re using a regular insecticide, you may wait until the end of June to spray, and then you’ll need just one application to get all of them.
If you don’t want to use an insecticide at all, you can certainly just come out in August and pick off all the bags – or you could pick them off earlier in the season. Make sure that you get all of them, and don’t just throw them on the ground. You’ll need to destroy the bagworms. They’ll chew through a trash bag, and they’ll climb out of bucket. So, you’ll need to make sure that you get rid of them, or you’re just moving the problem.
This feature story prepared with Jennifer Smith, Kansas State University Research and Extension Horticulture Agent, Douglas County. For more information, visit your local county extension office or visit our website at KansasGreenYards.org.