Gypsy Moth in the Pacific Northwest

1992 Asian Gypsy Moth Eradication Program

Gypsy moth larva

In 1991, nine Asian gypsy moth males were caught in the vicinity of Tacoma, Washington, and one was caught in North Portland, Oregon. These moths were caught in pheromone-baited traps during surveys conducted annually by the Oregon Department of Agriculture and the Washington Department of Agriculture.

During April and May, 2002, an eradication project was conducted in both states by the Washington Department of Agriculture, Oregon Department of Agriculture, USDA APHIS, and USDA Forest Service. Three applications of Bacillus thuringiensis var. kurstaki were applied aerially to 132,700 acres in Washington and 11,500 acres in Oregon. The cost of the eradication project was about $9,800,000. Also, pheromone trapping in 1992 was greatly intensified around all ports and along all waterways in both Oregon and Washington; in fact, the 1992 trapping costs were almost as high as the eradication project. No moths were caught in pheromone traps in 1992 through 1994, so this project was deemed successful.

Lane County Eradication Program (mid-1980s)

defoliation by gypsy moth larvae

The Oregon Department of Agriculture is the lead agency for the gypsy moth detection program in Oregon. Agencies involved in the eradication program included the Oregon Department of Agriculture, USDA APHIS, USDA Forest Service, Oregon Department of Forestry, and private timber companies.

Three gypsy moths were initially detected in 1982 in the town of Lowell in west-central Oregon. These moths were caught in pheromone-baited traps during surveys conducted annually by the Oregon Department of Agriculture. In 1983, four more moths were caught in Lowell. After the trapping program was intensified in 1984, over 19,000 moths were caught in or near Lowell.

In the late spring of 1985, 226,045 acres were treated with Bacillus thuringiensis var. kurstaki. Later that fall, the intensive trapping program identified additional infested areas in the same general area. Followup treatments with Bacillus thuringiensis var. kurstaki were applied in 1986 (189,011 acres), 1987 (7,235 acres), and 1988 (2,995 acres). In addition to the aerial application of biological insecticides, State and federal quarantines were established in 1985 covering ~1,200 square miles to prevent people from moving gypsy moths out of the infested area. No further treatments were required after 1988. The total cost of the Lane County eradication program (including detection, eradication, and trapping) from 1984 to 1989 was about $18,000,000.

Other Eradication Projects

adult female gypsy moth with an egg mass

In addition to these two large programs in the Pacific Northwest, there have been new introductions of European gypsy moth discovered almost every year in either Oregon or Washington, or both. There have also been occasional discoveries of single Asian gypsy moths in these traps. All of these positive catch sites have been intensively monitored, and where reproducing populations have been found, smaller scale eradication projects have been conducted successfully.

Sometimes the source of new gypsy moth infestations can be identified. For example, an infestation in Bend, Oregon (Deschutes County) was traced to vintage car parts that had been purchased on E-bay and shipped to Bend from Connecticut in January 2005. After pheromone traps caught gypsy moths in the general vicinity in 2005 and 2006, "entomological detectives" from the Oregon Dept. of Agriculture were able to pinpoint the source by finding older eggmasses on those car parts. After 533 acres were treated using 3 aerial applications of B.t.k., no additional moths were trapped in the area in 2007.

Current Status in the Northwest

Oregon: A total of 11 moths were trapped in Oregon in 2007; view additional information about the 2007 detections. A 336-acre eradication project was conducted in 2008 in Shady Cover, OR (Jackson County).

Washington: In 2007, 24 moths were trapped in 10 different locations (view a 2007 summary). these sites will be carefully monitored in 2008, but no eradication projects are planned. View information about the gypsy moth detection program in Washington.

Much of the information on this webpage was provided by David R. Bridgwater, USFS-retired.