Symptoms of Bagworm
You know bagworms are at work when you see their silken pouches dangling from branches on your trees or shrubs. Also, the foliage of the bagworm-infested trees is ragged or even stripped off altogether. You may overlook their presence while the needles on their bags are still green, but eventually they turn brown and the bags are more obvious. Many conifers (cone-bearing needled evergreens) are killed if completely defoliated by bagworm. Assume that if you see a few bags on a tree, that there are many more that are not visible. Consider taking some action right away to prevent more damage to the affected tree and neighboring plants.

Plants Affected
Most common targets:
Arborvitae
Cedar

Other targets:
Cypress
Fir (Abies)
Hemlock (Tsuga)
Horse Chestnut (Aesculus hippocastanum)
Maple (Acer)
Spruce (Picea)
Sycamore (Platanus occidentalis)
Willow (Salix)