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BAGWORMS: Control the Destruction!

Bagworms. Everyone’s favorite little defoliator, right? These clever moths begin life as tiny caterpillars and use the foliage of trees and shrubs to protect themselves so they can mate and create even more bagworms. They can be extremely destructive, and their cone-shaped cases oftentimes go unnoticed as “pinecones” or some other doo-dads that almost pass for something that belongs on the tree!

The Bagworm Lifecycle

This moth begins life as a tiny caterpillar (“worm”) when it hatches from its egg late May to early June. This larva and 300-1000 of its brothers and sisters emerge from the case and are so small that they generally go unnoticed, then using a strand of silk, they can catch a free ride on the wind right onto your favorite tree. As they feed on needles or leaves they begin to weave together a case, or bag, of their own from the chewed plant material. This case can help protect them from predators and temperature extremes. As they feed, the worm and the case both grow – up to 2 inches long.

Late in August the mature larvae will secure the bag to a branch and close themselves up in the case, where they pupate. Bagworms are stuck in the olden days. While the male becomes a small furry moth and flies to the females to mate, the ladies…well, they never get to venture out and die after mating. Tough life.

Can bagworms kill my trees and shrubs?

YES – Bagworms can disfigure or even kill evergreens in a hurry as they feed on needles. If you have a minor infestation of bagworms, pick off the cases and throw them away in a sealed grocery bag, place in a bucket of soapy water, or burn them if that gives you satisfaction. If your trees have more than a few however, give us a call so we can perform properly timed insecticide sprays. Remember, every case can have 300-1000 eggs, so you don’t want the population exploding from one year to the next!

What species are most at risk?

We see bagworms most commonly feeding on spruce, arborvitae, and junipers. They can also feed on deciduous trees, however that damage is not usually concerning or long lasting.

When is the best time to spray for bagworms?

Larvae are active June through August. Sprays are most effective when before the larvae are protected by their cases, so the earlier in the season, the better. 

How does Arbor Aesthetics manage bagworm infestations?

Arbor Aesthetics offers a two-time foliar spray treatment of either Permethrin or Bifenthrin insecticide while the larvae are actively feeding on your trees and shrubs. We closely monitor bagworm larvae activity so the timing of the treatments is most effective. We recommend repeating this treatment annually for at least 2-3 years before re-evaluating for control.

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