Male Asian gypsy moth. Photo courtesy of Oregon Department of Agriculture.

Male Asian gypsy moth. Photo courtesy of Oregon Department of Agriculture.


In 2015, the Asian gypsy moth, a plant-eating invasive species, was detected in Portland’s Forest Park and in St Johns. The moths were found in traps placed throughout the region by the Oregon Department of Agriculture. Because there is a national policy to keep gypsy moths from establishing, a regional technical working group was formed to review the situation and create recommendations to Oregon on how to handle the situation. To view the working group report please visit: Report from the Technical Working Group in Response to the Asian Gypsy Moth Captures (Washington-Oregon 2015).

The recommendations included eradicating gypsy moth populations in the area the spring of 2016. Establishment of Asian gypsy moth represents an unprecedented threat to forest ecosystems and would result in increased pesticide use, based upon the need of private landowners to conduct ongoing treatments to mitigate damage. Homeowners would also face damage to plants and trees on their property. For agriculture, having to live with gypsy moth would also increase production costs and loss of markets through quarantines on nursery, horticultural, and forest products, including Christmas tree production.

The recommended treatment included aerial application of Btk, an organically approved product and natural-occurring bacterium that has been used safely and effectively in other gypsy moth eradication projects in Oregon since 1984. The United States Department of Agriculture conducted an environmental assessment through the NEPA (National Environmental Policy Act) to review this recommendation. The Environmental Assessment for Gypsy Moth Management in the United States | A Cooperative Approach and Record of Decision is available for review here.

Frequently Asked Questions

What does a gypsy moth infestation look like?

Check out this video from Hanover Township in Pennsylvania from June 2015:

Read the article here: Invasion of Gypsy Moth Caterpillars


The following is an excerpt from Oregon Department of Forestry Gypsy Moth Fact Sheet: 

"The European gypsy moth (EGM) was introduced in 1869 in Massachusetts as a potential silk-producing species. By 1889 it began causing significant damage to hardwood forests of the northeastern U.S. Attempts to eradicate the pest in the 1920's were unsuccessful. 

Between 1970 and 2013, more than 80 million acres of forests were defoliated by EGM in the eastern U.S. Programs to suppress outbreaks and eradicate satellite populations have been successful. A national Slow the Spread program has reduced the westward expansion by 70 percent to about three miles per year. 

Gypsy moth surveys have been conducted by the Oregon Department of Agriculture (ODA) and its cooperators since 1979 using synthetic pheromone trapping. EGM has been detected nearly every year. In 1984, more than 19,000 EGM moths were captured in Oregon in Lane County. Although AGM is not established in the U.S., single AGM moths were found in Oregon in 1991, 2000, 2006, and two AGM moths 2015.

Because of its good record of catching populations early, Oregon has been 100 percent successful in eradicating both EGM and AGM. Today, no quarantines for EGM or AGM exist in Oregon."

To view the fact sheet, visit: ODF Gypsy Moth Fact Sheet

For more on ODF's invasive species program, visit (click on invasives'): ODF Forest Health Program Information

Where was the treatment area?

In Portland, the treatment area encompassed 16 square miles. It included Forest Park, a portion of Linnton, the St. Johns neighborhood and a portion of the Port of Portland.

To see the treatment area, visit the Oregon Department of Agriculture's treatment area map: Gypsy Moth Treatment Area

how can i learn about the environmental impact of the gypsy moth treatments?

An Environmental Impact Statement for all gypsy moth programs (Asian included) was completed in 2012 and is available on the USDA Forest Service website at: USDA Forest Service | Environmental Impact Statement

What Can I do to help?

A post-treatment Asian gypsy moth trapping program began in May 2016.  The trapping program is crucial to evaluate the success of the treatment program and to pinpoint any residual gypsy moth populations. Traps were placed throughout the treatment area in varying densities. If there is a trap on your property, try not to disturb it. 

Most importantly, report invasive species sightings to: 1-866-INVADER

How many times was btk be sprayed?

"Aerial application of Foray 48B provides the lowest risk option available, as determined by the science technical working group. Three applications are planned at approximately 7-14 day intervals. The spraying would be done by helicopter, beginning at first light. Approximately 0.5 gallons of Foray 48B would be applied per 1 acre. The first application would take place in late April or early May. The same application procedure has been successfully used to eradicate gypsy moth populations in Oregon and in the western part of North America."

What formulation of Btk was used?

Foray 48B was used. To view the product label on the manufacturer's website visit: Foray 48B Biological Insecticide. 

Is the use of btk for gypsy moth treatment safe?

The Oregon Health Authority has an excellent FAQ section on Btk which you can visit here: Btk Insecticide Facts and Questions.

Their website discusses the impacts on immune-compromised individuals and how to prepare for the treatment.

An excerpt from their website states: "It is unlikely that indirect exposure to Btk will result in adverse health effects in non-target organisms, including people. People working in occupational settings, directly exposed to Btk, for long periods of time have had mild skin irritation or short term breathing problems. After a thorough review of the toxicity of Btk products, including both active and inert ingredients, the U.S. EPA, Health Canada, the World Health Organization, and many other groups categorize Bacillus thuringiensis as a least toxic method of pest control."


Asian Gypsy Moth: Threat and Opportunity, prepared by the Oregon Department of Agriculture 

Report from the Technical Working Group in Response to the Asian Gypsy Moth Captures (Washington-Oregon 2015), available on the USDA-APHIS website

Oregon Department of Agriculture Press Release Jan 06, 2016,

World Health Organization's Report on Microbial Pest Control Agent: Bacillus thuringiensis (Btk) 

Oregon Department of Agriculture Twitter page. Check for latest information about the ODA.


Poster Banner Art by Chris Hedstrom, biological control specialist and assistant imaging specialist for the Oregon Department of Agriculture.