Courtesy of USDA ARS
European gypsy moths were found in alarming numbers this summer in Washington in two places about as different as two places can be.
The Washington Department of Agriculture trapped 16 gypsy moths in Yacolt, a small town 20 miles northeast of Vancouver and just outside Gifford Pinchot National Forest in southwest Washington.
Meanwhile, WSDA caught eight gypsy moths in Seattle, including six on densely populated Capitol Hill.
In both places, gypsy moth eggs likely came West attached to the property of new residents, WSDA Pest Program Manager Jim Marra said.
The leaf-eating pest has gained a permanent foothold in 19 eastern states and travels via picnic tables, birdhouses, patio furniture and other common household goods kept outside.
WSDA will look this month for gypsy moth eggs in Yacolt and on Capitol Hill. If any are found, the department will propose an eradication treatment, Marra said.
“Egg masses are very hard to find,” he said. “We figure for every egg mass found, there are others we haven’t found.”
For more than 30 years, Washington and Oregon have been on guard against European gypsy moths and their more dangerous but rarer kin, Asian gypsy moths.
On its website, WSDA calls gypsy moths, “The most damaging forest insect pest ever introduced into North America.”
The insect in its caterpillar stage has an indiscriminate taste for the leaves of shrubs, vines and trees, including apple trees.
The gypsy moth has defoliated thousands of acres and caused millions of dollars of damage in the East, according to the U.S. Department of Agriculture.
WSDA has a no-tolerance policy when it finds eggs. The stance has put it at odds with activists that advocate a no-spray approach, especially in Seattle.
After trapping only one gypsy moth last summer, WSDA caught 27 this summer.
Besides Yacolt and Seattle, WSDA detected single gypsy moths at Neah Bay in Clallam County, Port Townsend in Jefferson County and Lake Whatcom in Whatcom County.
In Oregon, four European gypsy moths were trapped this summer, all west of Grants Pass, state Department of Agriculture spokesman Bruce Pokarney said.
“It doesn’t indicate anything we have to treat next spring,” he said. “Four is not a bad number.”
Since 1979, WSDA has conducted 90 eradication treatments against gypsy moths. Only one eradication effort has occurred east of the Cascades. Marra said he believes gypsy moths are more likely to appear in Western Washington because more people migrate into that region.
WSDA in 2013 ground sprayed 10.5 acres in the neighboring King County cities of Tukwila and Renton with Bacillus thuringiensis kurstaki. The biological pesticide is sold as Foray and commonly used in organic agriculture, according to the Washington Department of Health.
From the air, WSDA sprayed 180 acres with disparlure, a synthetic pheromone that confuses male gypsy moths and prevents mating.
Marra said he believes the chances of finding eggs in Yacolt is high. On Capitol Hill, where fewer moths were detected, Marra estimated the chances of findings eggs are 50-50.
In 2006, WSDA aerial sprayed 100 acres on Capitol Hill and the adjacent Madison Valley neighborhood.
A group called No Spray Zone protested the application and remains a critic of applying pesticides. The group argues the state is too quick to spray and that there are alternatives to chemicals that change the environment.
The group’s director, Claude Ginsburg, suggests mass trapping. “I certainly don’t want to see a gypsy moth infestation in Washington state,” he said.
WSDA rejected mass trapping in 2013 as inefficient and probably ineffective. Releasing sterile male gypsy moths to control the population is largely untested, according to WSDA.
No one formally opposed the 2013 spraying, according to the project’s environmental impact statement. Marra said the public has generally supported eradication efforts.
“We have no permanent population of gypsy moths currently, and the purpose of this program is to keep it that way,” he said.