City of Edmonds: Tent caterpillar season no reason to panic

Western Tent Caterpillars
Western Tent Caterpillars

The City of Edmonds reminds residents that for the next few weeks, the eggs of Western tent caterpillars will be hatching and the larvae will be foraging on the leaves of native trees and shrubs such as alder, apple, ash, birch, cherry and wild roses.

Says the city announcement:

The caterpillars secrete silk to create a web-like structure that we call a tent, suspended from the branches and twigs of the host plant. After eight weeks of growth the caterpillars form cocoons and complete their metamorphosis into adult moths in another two weeks. The adult moths begin the life cycle again by laying eggs in late spring and early summer.

Tent caterpillars are native insects that are naturally controlled by ecological factors such as diseases, parasites, birds, the scarcity of food and weather conditions. These natural enemies soon bring tent caterpillars under control in a 3-5 year cycle. As damaging and unsightly as tent caterpillars may appear, trees and shrubs that are in good health will survive the activity and in 4 to 6 weeks the damaged plant will rejuvenate and put on new leaves.

The Edmonds Parks Department is committed to an environmentally sensitive approach to pest management. Therefore we ask the public to tolerate these insects because they are part of the natural ecological process for our area.

3 Replies to “City of Edmonds: Tent caterpillar season no reason to panic”

  1. Thanks for the very excellent description of the tent caterpillars by the Edmonds Parks Department. It should reassure people that they don’t have to panic and remove every “tent” they see. Alder trees are very susceptible also.


  2. Great information to know. Thank you. I distinctly remember back in the early 70s standing in my many fruit trees front yard with friends all adorned and masked with scarves (now we would look like the bloods and crips) and holding scary torches of fire at caterpillar time. Yikes!


  3. If everyone in our city left the caterpillars to themselves they would take over Edmonds and ruin our trees and hedges. They spread very fast. Cutting out tent caterpillars and putting them in water to eliminate them in the garbage is an environmentally safe way to get control of the situation. The only problem is when the alder wood trees have caterpillars one has to have them sprayed.


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