Bagworms can be a devastating landscape pest.
Populations of this voracious pest can build rapidly, with each female bagworm (Thyridopteryx ephemeraeformis) depositing up to 1000 eggs during autumn. From May to June eggs hatch and young caterpillars begin feeding and constructing their very distinctive protective cases or “bags.” These bags measure about one to two and half inches long and are attached to the host plant. The caterpillars then remain mostly hidden, feeding upon the foliage of host plants from the safety of the bags throughout their life cycle. Evergreen trees can be killed entirely through defoliation and deciduous trees seriously damaged. This pest can be particularly devastating in landscapes possessing rows of trees in a privacy border formation as it spreads easily from tree to tree.
Although this pest is not particular about its diet, feeding upon a variety of host plants, it can be very easily recognized via its protective bags. Early detection and removal of the bags can help to prevent plant damage and adequately control small populations of bagworm. However, large populations may require treatment. Although there are a number of over-the-counter treatments labeled for use on bagworm, they tend to be more effective and plant damage is limited when caterpillars are young (early summer).