The Evergreen Bagworm: A Silent Threat To Your Trees

Anyone who’s ever had an issue with an Evergreen Bagworm infestation knows the devastation they bring to trees. The poor trees become increasingly sparse in their pine needle distribution until they eventually lose them all and die. This is a sad end to the beautiful evergreen trees we all love. Thankfully, there are ways to save your trees if you know what to do.

The Evergreen Bagworm: The Silent Killer of Trees

In the world of pests that threaten the health and beauty of trees, few are as notorious as the Evergreen Bagworm. Despite its name, the Evergreen Bagworm is not a worm but a moth in its larval stage. These deceptive creatures can wreak havoc on various evergreen and deciduous trees, causing significant damage and even death if left unchecked. (1)

Understanding the Evergreen Bagworm

The Evergreen Bagworm, scientifically known as Thyridopteryx ephemeraeformis, is a species of moth that belongs to the family Psychidae. These small, inconspicuous creatures owe their name to the distinctive protective casing they construct around themselves, known as a bag or case. Bagworm larvae attach bits of plant debris, such as leaves, twigs, and bark, to their bodies using a silk-like thread they produce. Over time, this structure grows and becomes their portable shelter and means of camouflage, making them appear as small bags hanging from tree branches.

Life Cycle of the Evergreen Bagworm

Effective management of the Evergreen Bagworm depends on knowledge of its life cycle. These moths’ reproductive cycle starts when the female adult lays her eggs inside her own bag. The bag is then left hanging on the tree after she passes away.

These eggs are dormant all winter long, hatching in late spring or early summer to produce tiny larvae. After hatching, the larvae leave the bag in search of an appropriate host tree. They start building their bags once they find a suitable location, using silk produced by special glands in their bodies.

The bags start out small and unnoticeable, but as the larvae develop, they periodically emerge to replenish their casing with additional plant debris. These cases grow bigger and more obvious over time.

The larvae go through several molts as they grow, shedding their skin each time to accommodate their expanding size. A new bag is built for each instar, or stage, of growth. Late summer or early fall is when bagworm larvae typically reach their final instar. The larvae have reached this stage, which lasts for about six weeks, and are prepared to pupate.

Within the protective case, the moth changes from its larval stage to its adult stage. Invisibly hidden, the pupae grow inside the bagworm cases. By making a circular opening in the case, the adult moths crawl out after about two weeks. The larger, wingless female moths stay close to the original tree, while the males, which are darker, smaller, and have clearer wings, fly off in search of females.

The Destructive Nature of the Evergreen Bagworm

Evergreen Bagworms may at first glance seem harmless, but if they are not controlled, they can seriously harm trees. These pests are voracious eaters who prey on various tree species’ foliage. They hide until the infestation is severe thanks to the protection and camouflage offered by their bags.

Defoliation brought on by bagworm larvae feeding on the tree’s leaves makes it more difficult for the tree to photosynthesize and produce the nutrients it needs to grow and survive. The feeding activity also weakens the tree, making it more susceptible to other illnesses, pests, and environmental stressors. Evergreen Bagworms can lead to tree decline and, in some cases, tree death if left untreated.

 

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