Bagworm mitigation #772725 - Ask Extension

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Bagworm mitigation #772725

Asked September 22, 2021, 3:56 PM EDT

Hi, I live in urban Des Moines and realized this summer that I have a bagworm infestation on a large evergreen shrub. Actually, I am realizing now that I've had bagworms on this shrub for several years and didn't know it. Surprisingly the shrub itself looks relatively healthy. There are many bags on it now, some from prior years and I'm sure some new ones that have worms/eggs inside. My plan is to manually pull off as much as I can this fall, and then maybe use insecticide in the spring. When is it time to start the project of pulling them off?

Polk County Iowa

Expert Response

Hi Kristen:

Thank you for your message and for contacting Iowa State University.  Our online article about bagworms is at https://hortnews.extension.iastate.edu/bagworm

The bagworm caterpillars have finished feeding this season and insecticides sprayed now will have no affect.  You are correct to pick off bagworms you can safely reach, and discard.  Bagworm removal can happen anytime between now and next June, when the eggs inside the bags will start to hatch and start the next generation of caterpillars and damage.

The insecticide spray next spring should not be applied until the bagworms hatch, which is usually in June.  Sprays are most effective against the tiny bagworms that are difficult to see.

Thanks.

Donald Lewis

Donald Lewis Replied September 22, 2021, 6:11 PM EDT

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