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Bagworms

Tim Gibb, Extension Entomologist

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Bagworm Caterpillar in Its Bag
A Bagworm Caterpillar in Its Characteristic "Bag"

Bagworms have recently become very active throughout Indiana and are causing considerable panic by those caring for junipers, arborvitae and other trees and shrubs. These insects live singly within a small spindle shaped bag which they carry with them as they feed. This bag, made from bits of foliage tied together with silken threads, expands as the caterpillar grows and offers protection from predators and parasites. Bagworm caterpillars feeding on the foliage of the tree or shrub and may cause very obvious defoliation by July or August.

The best time to spray insecticides for these insects has passed (mid June), however, if the bags are still 1 inch or less in length some control may still be achieved. If the bags are large, and the trees are small, picking the bags off and destroying them may be the best option. Please refer to the extension publication E-27, Bagworms (PDF 29K), available through the Purdue Entomology website for a list of chemical control options.


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Last updated: 27 July 2001/tlm.
The Plant & Pest Diagnostic Laboratory at Purdue University.