The Washington State Department of Agriculture plans to spray a biological pesticide from a low-flying airplane over a total of 1,706 acres to kill gypsy moth caterpillars in King, Kitsap and Snohomish counties.
If weather permits, the spraying will begin Saturday. The department plans to hit each of four areas at least three times and expects to wrap up the operation by mid-June.
Gypsy moth caterpillars eat the leaves of hundreds of trees and plants. The pests are established in the East and Great Lakes regions. Western states trap gypsy moths in the summer and in the spring spray places that appear to have a developing population.
Most years since 1979, Washington has sprayed or trapped the caterpillars as they emerge.
The department uses Bacillus thuringiensis var. kurstaki, or Btk. The pesticide is not a danger to humans or the environment, according to the department.
If the department didn’t eradicate gypsy moths, homeowners and business owners would take matters into their own hands and release more pesticides, according to a department assessment.
Btk is sticky, but can be washed off with soap and water, according to the department.
The department will spray:
• 699 acres over Martha Lake in Snohomish County. Only one gypsy moth was trapped there last summer, but it was of the rarer Asian type. Asian gypsy moths eat a wider variety of plants and are more mobile than European gypsy moths. Martha Lake is a commercial and low-density residential area.
• 438 acres over Crosby, an unincorporated rural community in Kitsap County. The department detected four European gypsy moths there last summer.
• 299 acres over Gilberton, another community in Kitsap County. Nine European gypsy moths were caught there.
• 270 acres over Union Hill-Novelty Hill, a rural area in north King County. The department trapped six European gypsy moths there.