Early June is the time of year bagworms become most destructive. You may be familiar with the Christmas tree ornament like silken bags attached to branches of evergreens. These interesting cocoon-like casings expel hundreds of bagworm larvae that go to work on your prized plants.

Bagworms are particularly destructive in early summer. The caterpillars (larvae) emerge from their bags (that Christmas tree ornament), and begin feeding on the first thing in sight. They will continue to eat through late summer when the next generation of females begin the process of making their silken bags to start it all over again.

Bagworms will feed on a variety of plant species, but are most destructive on juniper, arborvitae, spruce, pine and cedar. They begin by decimating massive sections of foliage. Sometimes the plant can recover once the bagworms have been treated, but it will usually require replacement of the plant.

Once the caterpillars emerge from the silken bag where the over-wintered, they begin making a soft, balloon-like bag for themselves (this is where the term bagworm comes from). The caterpillars will spend their entire lives in these bags. There is space for the head to emerge, and their feet can reach the branches, but other than that they are completely covered. As the caterpillar grows it expands its bag, adding twigs and plant material as camouflage.

Treatment can be effective if the right product is chosen, and it is performed at the appropriate time:

  • Timing: You should treat for bagworms when the larvae are young. This is the time they are actively feeding (so the product will be most effective), and you can minimize damage. You can also remove the bagworm’s bag over the winter. Taking pruning shears, simply remove the casing and destroy. This technique is best for small infestations. For larger populations, an insecticide in necessary.
  • Product: Applying the right product at the right time is crucial for bagworm control. Insecticides must be applied after the larvae emerge, but before they grow large. In the mid-south area that is early to mid June. Use caution when choosing an insecticide. Some insecticides can encourage other parasites (like spider mites). Your local lawn and garden center should be able to help you choose a product labeled for bagworms. As with all products, be sure to read labels carefully, and follow directions exactly. And…when in doubt…call a professional.
Bagworms do not have to be a death sentence for your evergreens, but they do require direct, intense attention. The time is now… act quickly.