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Wash. State Ag Officials Considering Options After Biggest Catch of Gypsy Moths In 22 Years

Gypsy moths are back in Washington State – with a vengeance. Officials at the Washington State Department of Agriculture say they’re evaluating options after the agency’s annual trapping program caught 117 of the invasive species this summer – the highest number in more than 20 years.

It’s normal for Agriculture technicians to find one or two gypsy moths in those triangular cardboard traps you sometimes see on trees.

“But one day we started having catches of like, eight, six, 14 in a trap, all in a very concentrated area,” said Karla Salp with the state Department of Agriculture.

The area was between Puyallup and Graham in Pierce County. A team that included Salp went to investigate. The traps led them to an ornamental plum tree.

“We found about 100 live female moths on this tree. And that’s a major concern because each moth, each female moth, can lay up to 1,000 eggs. So an infestation can really explode into a major problem, very quickly,” she said.   

Salp says it was the first time they had ever found an infestation of live females.In addition to the females, the state trapped about 80 males in that area alone – more than three times the number in the entire state last year.  

Gyspy moths can defoliate entire forests if they become established.

The best explanation for the high numbers here is the spike in populations in New England, where they were first introduced. People who drive from the East Coast can unwittingly bring egg masses with them. Salp says gypsy moths are the most damaging forest pests ever introduced to the United States.

“This year, approximately a third of the entire state of Massachusetts was defoliated from gypsy moths. We do not want that to happen here in our state, so we’ve been monitoring them for over 40 years, to make sure that they don’t become established here.”

Now, AG teams are out doing surveys for egg masses till the end of the month, which will help determine if and where they need to spray this spring, before the hatch.

A proposal must go out for public comment, but Salp says they’ll likely use an organic bacteria-based pesticide called BTK that was used in several areas last year including Tacoma, Kent and Seattle’s Capitol Hill neighborhood.  

Bellamy Pailthorp covers the environment for KNKX with an emphasis on climate justice, human health and food sovereignty. She enjoys reporting about how we will power our future while maintaining healthy cultures and livable cities. Story tips can be sent to