Bagworm larvae injure plants when they feed on needles and leaves. Young caterpillars feed on the upper epidermis of host plants, sometimes leaving small holes in the foliage. Damage by mature larvae is especially destructive to evergreen plants. Trees such as sycamore, willow, and other deciduous trees, usually refoliate after an episode of heavy defoliation. Unfortunately, bagworm infestations generally go undetected until damage is complete, and the large bags constructed by this pest are very conspicuous. Early detection of an infestation requires careful examination of host plants for the presence of small bagworms attached to the leaves or needles.