WOODWAY — They’re the worst of tenants. They’re destructive, they eat everything in sight and they don’t know when it’s time to leave.
Nearly 1,300 acres in Woodway and an Everett neighborhood south of Mukilteo Boulevard will be sprayed with insecticide — dropped from a height of 100 to 200 feet by an airplane — to stop the moths from spreading and to prevent them from gobbling up forest foliage.
The first Hokkaido gypsy moth showed up in Woodway last year. It was reportedly the first of that type of moth found in the United States. Moths near the Boulevard Bluffs neighborhood have also tested positive for both European and Asian genetic traits, and the state Department of Agriculture intends to eradicate them.
“This is really bad because they’re very destructive to environment in the U.S.,” department spokesperson Karla Salp said.
When there’s a moth outbreak, they can strip entire forests of their leaves.
Their favorite trees are oak, but they feed on up to 500 species.
“They’ll basically eat anything that is around,” Salp said.
Deciduous trees (the ones that drop and regrow their leaves every year) can potentially survive. But repeated defoliation will kill even a deciduous tree.
The Pacific Northwest’s iconic evergreen trees aren’t as resilient to the moths. Once stripped of foliage, the tree dies, Salp said.
A Hokkaido moth could have stowed away on a bulk cargo ship from an infested area across the Pacific Ocean.
The gypsy moth is considered the worst forest pest insect ever to find its way into the country, according to the state Department of Agriculture. It has defoliated millions of acres of trees and shrubs since first arriving in the United States in 1869, when a naturalist brought over a bunch of its eggs to crossbreed with silk worms.
The silk business didn’t work out, and some of those gypsy moths escaped.
More than 150 years later, 20 Eastern and Midwestern states have permanent infestations of the European gypsy moth. In 2015, the damage was so bad in Rhode Island that it could be seen from space. A year later, a third of the state of Massachusetts was defoliated by gypsy moths.
The gypsy moth was first detected in Washington in 1974. Since then, a few have have been trapped almost every year.
“The good news is that we have been trapping for over 40 years and we’ve prevented them thus far from getting established in Washington,” Salp said.
Last year, the state Agriculture Department used 20,000 traps and caught 14 moths.
A permanent population does not seem to have gained a foothold. Washington has sprayed for moths almost annually since 1979.
In recent years, the moths have been trapped locally on Camano Island, in Martha Lake, Mukilteo, Oak Harbor and Snohomish. The moth trapped near Martha Lake resulted in aerial spraying over about 700 acres last May.
Treatment for the 1,300 acres in Woodway and in Everett could take place anytime between now and June. It all depends on the weather, Salp said, and on when the moths hatch.
The state Department of Agriculture will spray a soil bacteria called Bacillus thuringiensis var. kurstaki, or Btk, one to two weeks after the insects’ eggs hatch. The insecticide is approved for use in organic agriculture, according to the state.
Treatment will cost nearly $300,000, with federal funds covering about 80%.
Julia-Grace Sanders: 425-339-3439; firstname.lastname@example.org.
People who would like to know exactly when the treatment will occur can sign up for notifications on the state Department of Agriculture’s website at agr.wa.gov/gypsymoth.