Tales From The Trails:

Asian Gypsy Moths Found in Forest Park

UPDATE from the Oregon Department of Agriculture:


At 8:05 this morning, Monday, May 2nd, the last and final Asian gypsy moth aerial treatment in the West Area along Highway 30 in Linnton, West Germantown Road, Linnton Park, Skyline Blvd, and Forest Park, has concluded.

Click here to see the map that shows the treatment areas.


You may have heard that gypsy moths were found last summer at several sites in Oregon and Washington, including Forest Park.


This is troubling news. If this invasive pest were ever to become established in our region it would quickly spread and cause serious ecological, economical, and social harm. In addition to gypsy moth larvae killing trees through repeated defoliation, our streams would be warmed by the loss of shade and also loaded with too many nutrients. Gypsy moths also displace our native moths and butterflies and can create human health problems.

Even worse, several of the trapped moths were Asian Gypsy Moths. This species can fly long distances, spreading quickly and consuming many important forest trees and plants, even conifers such as Douglas fir.

In the last 30 years, Asian gypsy moths have been detected in Oregon three times and successfully eradicated each time. This current presence of the Asian Gypsy Moth poses a significant risk for Forest Park and other urban trees.

In order to tackle this threat, a technical working group of experts from the United States and Canada weighed the options and determined that Bacillus thuringiensis kurstaki (Btk) would be the best option to target this pest. Btk is an organically approved product made from a natural‐occurring bacterium that has been used safely and effectively in other gypsy moth eradication projects in Oregon since 1984. Btk only controls early stages of moths and butterflies and does not harm other insects.

The USDA will soon make a final decision as to whether to treat a 16 square mile area over Forest Park, a portion of Linnton, the St Johns neighborhood, and the Port of Portland. Treatment would take place through aerial applications in April and May, at 7‐14 day intervals. Federal and state funding has been approved for this effort. We are hopeful that the USDA will be as successful at eradicating this invasive species as they have been in the past. 

To learn more, here are some resources available:



This article was written, in part, by Portland Parks & Recreation. 


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