WSDA Blog

Many people are familiar with springtime egg hunts and associate them with children, grass, and flowers. But when your job is protecting the state from invasive pests, egg hunts get turned on their head! In these egg hunts, the fewer eggs you find, the better.  

_{WSDA Pest Program staff use special mirrors to search driftwood for hidden spongy moth egg masses in Port Angeles.}

This October, members from WSDA’s Pest Program visited several sites looking for egg masses of the highly invasive spongy moth* (Lymantria dispar). It was part of an “alternate life stage survey” during which the program looks for evidence of the moths other than adults, such as egg masses, pupal casings, or shed caterpillar skins. Finding life stages such as egg masses could indicate that there is a reproducing population in the area.


_{In 2017, WSDA found these egg masses on a tree during an alternate life stage survey in Pierce County. Also notice the caterpillar frass (the black dots) at the base of the tree.}

The egg masses, which could be laid on virtually any outdoor surface, are generally oblong, light brown, and covered in fuzz from the female’s abdomen. The moths will sometimes lay their eggs in the open, such as on tree trunks. The egg masses can be tricky to see and the female moths often try to hide their eggs. When not hidden, they can also be camouflaged on tree bark. In previous years, WSDA found egg masses inside old tires, on tree trunks obscured by vegetation, and under large landscaping rocks.



The Pest Program normally conducts alternate life stage surveys where it has trapped multiple moths during the summer trapping season. But this year, the program received reports from U.S. Customs and Border Protection of numerous interceptions of the moths on container ships arriving in ports. Due to this increase in detections on ships, the program expanded its egg hunt to several port areas this fall.


_{Egg masses can hide anywhere - even on city artwork in Port Angeles.}

Spongy moth, which is established in several Eastern states and is native to Europe and Asia, can defoliate and even kill millions of trees in outbreak years. The moth makes its way to Washington each year, and the Pest Program sets traps to locate these unwelcome pests. They can come on items brought to Washington from Eastern states or through the ports. Despite repeated attempts to make Washington its home and devastate our trees and ecosystem, WSDA has an astounding record of successfully preventing spongy moth introductions from establishing in the state for over 50 years. These fall egg mass surveys are just one of the steps to continuing that track record of success.

* Previously known as "gypsy moth", the Entomological Society of America revised the common name in 2022.