06/15/2026
‼️ It’s bagworm season!‼️
Right now, bagworm caterpillars are hatching out. They feed on the foliage of a wide variety of trees including many common evergreens (cedars, junipers, spruce, pine, hemlock, etc), and deciduous trees (beeches, maples, linden, sycamore, willow, etc). They are not picky but often have expensive taste! They can often be seen feeding on tricolour beech, Japanese maple and blue spruce.
Bagworms use foliage of the plant and their own silk to knit a “bag” (their future cocoon). As they move about the plant continuing to devour foliage, they bring their “bag” with them. At this stage, they could be described as “half in the bag”. Part of their body is visible as they feed but they retreat into the “bag” when startled.
After a few weeks of active feeding, the mature caterpillars attach their bag to the underside of a leaf or branch and seal themselves in their completed cocoon. Inside the cocoon, bagworms will pupate and mature to moths. The male moth will emerge to seek out the wingless females. The female will never leave her bag but will leave behind hundreds of fertilized eggs when she dies.
Bagworms are best controlled by removing all the cocoons you can see (and reach) and/or by spraying foliage with BTK during their feeding phase. Contact sprays (soap or conventional insecticides) are largely ineffective since the caterpillars are mostly protected by their bag.
BTK is a safe and effective bacterial spray. To apply, mix 3mil per litre of water and apply with a pump sprayer. BTK will remain on foliage 10-14 days. Re-apply after heavy rain. As the caterpillars feed on the sprayed foliage they will ingest the BTK. Once infected with BTK, they will die in a few days.
NOTE: BTK is only effective in June and July during their active feeding phase. Once they have sealed themselves in their cocoons, the only effective control is physical removal. Dispose of all picked bagworms in a sealed bag because they will crawl away. Any harvested cocoons could be a source of eggs and should be included in the trash. Never just discard them in the garden…they will easily re-infest your plants!
