Bag Worms

Identification

Size: 5–25 mm long (larvae inside cases)

Color: Brown or greenish, often hidden inside a protective case

Description: Bagworms are caterpillars that live inside protective bags made from silk and plant material. They attach these bags to trees and shrubs and feed on the foliage. They are most commonly found on evergreen trees and can cause serious plant damage if left untreated.

Bagworms are outdoor pests that primarily target trees and shrubs, especially evergreens such as cedar, spruce, and juniper. The larvae build protective cases using silk and pieces of the host plant, which allows them to blend in with their surroundings. These cases hang from branches and move slightly as the insect feeds inside.

As bagworms feed, they chew through leaves and needles, gradually stripping the plant of its foliage. This feeding weakens the plant and can lead to browning, thinning, and eventual death if the infestation becomes severe. Deciduous trees may recover, but evergreens are more vulnerable to permanent damage.

Bagworms are most active in late spring and summer when larvae hatch and begin feeding. Early-stage larvae are easier to control, but as they grow, their protective bags become thicker and more resistant to treatment. Without proper management, populations can increase quickly and spread to nearby plants.

Bagworms are most easily identified by the small, spindle-shaped bags hanging from branches. These bags are made from plant material and often look like part of the tree, which makes them easy to overlook at first.

Look closely at branches for small cases that resemble cones or dried leaves. These bags may move slightly as the insect feeds or shifts position. They are usually attached firmly to twigs and can vary in size depending on the age of the insect.

Small hanging bags attached to branches
Bags made from leaves, needles, or twigs
Cases that resemble cones or plant debris
Slight movement from the bag when disturbed
Visible feeding damage on nearby foliage

Bagworm infestations often show up as visible damage to trees and shrubs. The most common sign is thinning foliage, especially on evergreen trees where needles begin to turn brown and fall off.

You may also notice small hanging bags attached to branches, which become more noticeable as they grow larger. In heavier infestations, entire sections of a plant may appear bare or dying due to feeding damage.

Regular inspection of trees and shrubs is the best way to prevent bagworm infestations from becoming severe. Check plants in late spring and early summer when larvae are young and easier to manage.

Hand-picking and removing bags can be effective for small infestations. Keeping plants healthy through proper watering and spacing also helps reduce stress and makes them less vulnerable to damage.

For ongoing or large-scale infestations, professional pest control services can help manage populations and protect your landscape over the long term.