Bagworm
Thyridopteryx ephemeraeformis

Bagworms are one of the most important pests of evergreen ornamentals in the South. Arbovitae and juniper are particularly susceptible. If infestations are heavy enough, they will strip evergreen shrubs of their foliage and cause branch dieback or death. Some hardwood species - such as maple, oak, dogwood, and willow - also are attacked, but rarely are they damaged as severely as conifers.

Identification:

The cone-shaped bags, which they form, easily identify bagworms. These are carefully interwoven using silk and bits of leaves and twigs from the host plant resulting in a well-disguised covering. The tops of the young larvae are shiny black and their body undersides are dull amber. When fully grown, the bagworms are a dull, dirty, gray with darker markings toward the head. The adult male develops into a moth that can fly, but the female remains grub-like and stays inside the bag.

Injury:

Bagworms consume the entire needle or leaf, leaving only the needle sheath or mid-rib. They usually feed on one branch at a time. An indication of damage is the presence of bags suspended from twigs and branches.

Biology and History:

Overwintering eggs begin hatching in early June. The tiny larva immediately begins to construct a tiny silken bag around itself and initiates feeding. Larvae and bags remain small (less than 1/4" long) for a few weeks and are not easily discovered. Feeding and molting continues until August when pupation occurs. Adults are active in late August and September. Only males leave the bag to mate with females which remain in the bags to lay overwintering eggs. Prior to molting and pupation, larvae attach the bag by silk strands to twigs and close the opening, protecting the larva.