YACOLT, Wash. — Washington Department of Agriculture searchers are working on a riddle: How did European gypsy moths get to rural southwest Washington?
The answer could help WSDA build a case for spraying pesticides and pinpoint where to apply them.
“If we don’t have the story, we typically treat a larger area,” said WSDA pest biologist John Townsend, the agency’s head gypsy moth hunter.
WSDA trapped 16 gypsy moths last summer near Yacolt, about 20 miles northeast of Vancouver in Clark County. The department also caught eight in Seattle, including five within a block on Capitol Hill.
All together, WSDA trapped 27 of the leaf-eating moths, which are established in 19 eastern states and can cause extensive damage to fruit trees. In Oregon, four gypsy moths were trapped near Grants Pass.
Both states have eradication programs to keep the pest out of the Northwest. Gypsy moth eggs typically travel west clinging to household goods, like patio furniture.
The numbers caught near Yacolt and on Capitol Hill were high enough for Townsend and his crew to begin combing sparsely populated woods and densely populated city blocks.
So far, the WSDA searchers have found only a spent egg mass near Yacolt. They have not discovered the original source of gypsy moths in either place.
“Quite often, we’re able to put the whole story together,” Townsend said. “In both Yacolt and Seattle, we have no idea, but we could figure it out.”
WSDA will search through the end of November. In the past, finding a live egg mass has virtually assured ground or aerial spraying, sometimes both. Before applying pesticides, WSDA must compile a report on the environmental consequences and solicit public comments. Eradication treatments in Seattle in previous years have drawn protests.
WSDA will decide later in the fall whether to spray in Yacolt or Seattle or both based on the evidence collected by Townsend.
The department also will seek advice from agriculture officials in other states, particularly in the West.
“If we have an established population in Washington, that puts other neighboring states at greater risk,” WSDA’s pest program manager, Jim Marra, said.
Even if no live eggs are found, “we’re going to consider the Yacolt site very carefully,” he said. “Anytime you find multiple stages of reproduction, that’s a concern.”
To say looking for an egg mass is like searching for a needle in a haystack understates the task.
Unlike haystacks, gypsy moths move. The next generation may be waiting to hatch hundreds of feet from where a member of the preceding generation was trapped.
Unlike a needle, the eggs don’t gleam in the light. Gypsy moths lay several hundred eggs in a quarter-sized brownish-orange mass that blends in with fall colors.
The egg mass can be attached to trees or property. They are found at ground and neck-craning levels and in between.
The spent egg mass found near Yacolt on Oct. 14 was a brownish smudge on a fir tree, but at eye level for WSDA agriculture technician Terry Fisher.
She earned lunch from Townsend by spotting where gypsy moths hatched last spring and finding a clue where eggs will hatch next spring.
Townsend, Fisher and two other WSDA agriculture technicians, Don Kitchen and Ryan Moore, returned to Yacolt on Oct. 22 and searched neighboring trees in unrelenting rain.
The dark day made spotting dull-colored egg masses even harder than usual. Hopes were raised briefly. But the suspected egg mass was actually frass, a pile of insect excrement.
The hunt was fruitless. “I’m surprised we haven’t found anything right around here,” Townsend said.
The next day the Olympia-based searchers were on Capitol Hill, an even more challenging setting, Townsend said.
There are more places to search and more people to ask permission from before searching private property. Egg masses have been found on objects such as fences, birdhouse, tires and rocks.
“That’s why we check everything,” Townsend said.