The state Department of Agriculture completed its spraying for gypsy moths in Western Washington on Tuesday after finishing the third treatment of an area above the Port of Tacoma.
A 7,000-acre site around the Port of Tacoma was the largest of the sites treated for Asian gypsy moths, an invasive species that can defoliate trees and shrubs and that reproduces quickly.
Sprayed as well were 600-plus-acre sites in Gig Harbor, Kent, Nisqually and near Lacey, plus a site in Seattle’s Capitol Hill neighborhood that had about 20 European gypsy moths.
In addition, the state of Oregon treated part of the Port of Vancouver for the Asian moths.
Gypsy moths have been found in Washington each year since 1977, but they have never established. Asian gypsy moths had not been seen since 1999, but 10 males were trapped in the state in 2015.
The aerial sprayings of the organic pesticide Btk started April 16 and were completed early because of nice weather. The pesticide does not harm humans, officials say.
The state will begin setting gypsy moth traps this summer to evaluate the effectiveness of this year’s treatments.