Bagworm caterpillars make distinctive 1.5 to 2 inch long spindle-shaped bags that can be seen hanging from twigs of a variety of trees and shrubs. Sometimes the bags are mistaken for pine cones or other plant structures.
Bagworms spread slow because the female can not fly, however, bagworms can be windblown or crawl to other host plants.
Bagworms are fond of junipers, cedars, arbovitae, spruce and white pine, but it also is found feeding on a number of deciduous trees and shrub species.
Damage to plants is caused by the larva eating plant foliage. If not controlled while they are small, the maturing larva can do considerable defoliation during the summer.
If you have bagworms in your landscape, you’ve probably been told there’s not much you can do but cut them out of the tree and destroy them. In fact, this is the best way to get rid of them.
In the fall, winter and early spring, before the eggs have hatched, the bags can be picked off the plant and destroyed. However, that’s not always easy to do, depending on the height of the tree.
The bagworm has some natural enemies, such as certain species of birds and parasitoid insects like the wasp that are able to tear open the bags and feed on the larvae. Unfortunately, in many cases other controls to eradicate bagworm populations must be used.