Bagworms Exposed: How to Identify and Stop Bagworm Damage to Save Your Evergreens

Mature Bagworm.

How to Identify, Stop and Prevent Bagworm Damage

As avid gardeners and nature enthusiasts here are Pryor’s Nursery, we understand the importance of maintaining the health and beauty of your evergreens. One common threat to these magnificent trees and shrubs is the presence of bagworms. In this article, we will delve into the world of bagworms, learn how to identify, stop and treat them, understand their life cycle, and most importantly, protect your evergreens from their destruction. Let’s dive in!

What are Bagworms?

Bagworms, scientifically known as Thyridopteryx ephemeraeformis, are moth larvae that belong to the family Psychidae. They are named after their distinctive characteristic: the bags they create and reside in. The bags are constructed from silk (like spiders) and pieces of foliage, bark, and other debris, providing camouflage and protection for the larvae.

How to Identify Bagworms

Identifying bagworms is crucial to take timely action against their infestation. Here are a few key characteristics to look out for:

  • Appearance: When fully grown, bagworm larvae resemble tiny caterpillars, about 1 inch long. The larvae have a yellowish-brown to dark brown color, with rows of small spines along their bodies. The most striking feature is their bag (cocoon), which hangs from the branches and is made of silk and plant materials.
Mature bagworm cocoon.
  • Bag Variations: The appearance of the bags can vary depending on the host plant. On evergreens, the bags are typically cone-shaped, tightly woven, and blend in with the tree’s foliage, making them harder to spot.
  • Damaged Foliage: Bagworm infestations often lead to visible signs of damage, such as defoliation, brown patches, and twig dieback. If you notice these symptoms, inspect the tree closely for the presence of bagworms and their bags.
Bagworm damage to the foliage.

Life Cycle of Bagworms

Understanding the life cycle of bagworms is essential for effective management. Here’s a brief overview:

  • Eggs: Adult female bagworms lay their eggs within the bags during late summer or early fall. Each bag can contain hundreds of eggs, ensuring a significant potential for infestation. Once the female lays her eggs she drops from the bag and dies.
  • Overwintering: The eggs remain inside the bags throughout the winter, protecting them from harsh weather conditions.
  • Hatching: Consequently, as temperatures warm in spring, the eggs hatch around mid-June, and the larvae emerge from the bags.
  • Larval Stage: The newly hatched larvae begin feeding on the surrounding foliage, constructing their bags as they grow. They go through several instars (growth stages) before reaching maturity.
Small bagworm cocoon forming as it eats the foliage.

  • Pupation: Fully grown larvae attach their bags to branches or other structures and enter the pupal stage, transforming into adults.
Mature bagworm cocoon hooked onto branch.
  • Adult Bagworms/Moths: In late summer, the adult male moths emerge from their bags, ready to mate and continue the life cycle.

Fun Fact: Adult female bagworms lack wings and are caterpillar-like with soft yellowish-white bodies. They remain within their bags, releasing pheromones to attract males, and die after laying their eggs.

How to Treat and Protect Your Evergreens for Bagworms

Now that we have a better understanding of bagworms and their life cycle, let’s explore some effective ways to protect your evergreens:

  • Regular Inspections: Perform regular visual inspections of your evergreens, especially during mid- June through August here in Maryland, DC, and Virginia when bagworm eggs and larvae are most active. Not only look for signs of bags but for larvae, and damage to catch infestations early. We regularly do checks of all the evergreens on our farm to ensure that we have only the best trees for your living fence privacy screen.
  • Handpicking – The Best EcoFriendly Bagworm Treatment: If you notice bags on your trees, carefully handpick them and destroy them by crushing or burning them. We have found this method to be most effective when the infestation is limited.
  • Pruning: When pruning, be sure to remove and destroy any branches or twigs with bags attached. It is equally important to properly dispose of the pruned material away from your evergreens to prevent re-infestation.
  • Biological Control: Encourage natural predators, such as birds that feed on bagworm larvae. In fact, Attracting beneficial insects to your garden can help control the population.
  • Insecticides: In severe infestations, or when other methods have proven ineffective, you may consider using insecticides. When the bagworm larvae are very small they are easy to control with insecticidal soap or horticultural oil sprays. As the larvae grow and mature, they develop 2 stomachs, at this stage, you will need traditional insecticides as the soaps are ineffective at this stage. Furthermore, always follow the instructions and safety precautions provided by the manufacturer.

Eventually, bagworms can pose a significant threat to the health and aesthetic appeal of your evergreens. The good news is the Thuja Green Giant is NOT a favorite food of the bagworms, therefore infestations are rare. Ultimately, by identifying these pests, understanding their life cycle, and implementing effective protection and treatment methods, you can safeguard your evergreen trees and shrubs. Remember, early detection and consistent management practices are key to preserving the beauty of your evergreen landscape. Enjoy the privacy of your evergreen living fence. If you need further assistance, Pryor’s Nursery is here to help you!