EUROPEAN GYPSY MOTHS have infested 19 states in the U.S. and are very destructive to trees and shrubs. Washington State has discovered gypsy moths every year since the late 1970s, but has never had a permanent infestation.
RESEARCHERS FROM the Washington State Department of Agriculture hang pheromone traps throughout the state every summer to trap male gypsy moths and figure out if infestations are in the making.
Scientists from the Washington State Department of Agriculture (WSDA) have proposed a plan to eradicate what they call an “infestation of European gypsy moths” in Yacolt.
If approved, the WSDA will spray a biological insecticide on 217 acres northeast of the small Clark County town this spring.
“The evidence of a reproducing population of gypsy moths in Yacolt is overwhelming,” said Jim Marra, manager of WSDA’s pest program. “Now is the time to stop it from spreading.”
To provide more information about the destructive gypsy moth and the proposed eradication program, WSDA officials will host a public meeting from 6:30 to 8 p.m., Tues., Feb. 17, at the Yacolt Primary School.
If approved, the eradication plan calls for three aerial applications of the biological insecticide Btk or Bacillus thuringiensis var. kurstaki. The sprays would take place in April and May and should, according to WSDA scientists, catch the moths during their most destructive, caterpillar stage.
“Any treatment with Btk is done in late April or early May, depending on the weather conditions – dry is better than rainy – and the emergence of gypsy moth caterpillars to consume leaves of trees and shrubs,” explains Mike Louisell, the WSDA’s public information officer.
The proposed insecticide, Btk, is considered very safe for humans and other mammals. In fact, Louisell says, Btk is approved for application on organic farms in Washington state and through the United States. Found as a spore in soil, the Btk is considered toxic to only one particular type of insect, the caterpillars of Lepidoptera (moths and butterflies). And even then, the caterpillars must ingest the leaves and shrubs that have recently been sprayed with the Btk. The insecticide does not linger long on the leaves, so scientists recommend three aerial applications for eradicating gypsy moth caterpillars.
Eating leaves is not a problem for these young gypsy moths, says Louisell.
“They’re voracious eaters, very destructive,” Louisell says. “The main thing is that they’re not native to our country and that causes problems for our agriculture and our resources.”
There are currently 19 states on the East Coast and in the Midwest that are listed as having “permanent gypsy moth infestations.” When people move to the Pacific Northwest, or even visit in their cars or RVs, they often unknowingly transport gypsy moth egg masses. WSDA researchers do their best to catch the masses that come in on shipping containers and other large-scale transportation mechanisms, but sometimes the moths hatch and start to reproduce.
Figuring out where the gypsy moths are, and then eradicating populations that have the capacity to do widespread damage is key to keeping Washington off the “permanent infestation” list, says Louisell.
“Gypsy moths have been detected in Washington every year since 1977, but permanent populations have not been established because of WSDA’s aggressive trapping and eradication efforts,” Louisell says.
The annual trapping program is what first alerted scientists that gypsy moths had landed in the Yacolt area.
“Every summer we trap for gypsy moths, primarily in western Washington because that’s where people relocate or come as tourists most often,” Louisell says. “The traps have pheromones in them to attract the male gypsy moths. They think there’s a female in there.”
This past summer, in 2014, the state set about 19,000 traps throughout western Washington as well as a few locations in eastern Washington. The researchers found significant numbers of gypsy moths in two locations — Seattle’s densely populated Capitol Hill neighborhood and in the sparsely populated town of Yacolt.
“We found 27 gypsy moths throughout western Washington this trapping season, and 16 of the 27 were found in Yacolt,” Louisell says. “That alone is not enough to recommend an eradication project, so we look for other evidence.”
What the scientists discovered was that the seven moths found in Seattle had not laid egg masses and, therefore, were not likely to produce the vegetation-eating caterpillars that cause so much destruction to trees and shrubs. However, the Yacolt moths had not only created egg masses, but scientists discovered spent egg masses in the area.
“So now we know that there’s a small population in the making in Yacolt and that this population is capable of introducing more gypsy moths,” Louisell says. “We don’t want it to grow.”
That’s why the state has proposed an aerial spray plan. The plan has to meet state and federal environmental constraints and pass public muster before being approved. However, Louisell says he sees no obvious impediments to the eradication project, slated for this spring.
“There are no active environmental groups opposing the project in Yacolt … and the history of using this Btk insecticide has a very good safety record. It is used in organic farming and it is known to be effective at removing these pests,” Louisell says.
Concerned members of the public, or even students who want to learn more about the WSDA’s pest program, are welcome to attend the public meeting on Feb. 17. WSDA scientists, including an entomologist, will be available from 6:30 to 8 p.m. Tues., Feb. 17 at the Yacolt Primary School, 406 W. Yacolt Road, Yacolt, to answer questions and provide more information about the proposed spray area and the gypsy moth infestation. The meeting format is casual and visitors may come any time between 6:30 and 8 and stay for as little or as long as they’d like, Louisell says.
“We’ll have displays and maps there, so people can come in and just look around,” he says. “They don’t even have to ask questions. But, if they do have questions, we’ll have a managing entomologist on hand to talk to them.”
For more information about the gypsy moths in Yacolt or to see a map of the proposed spray area, visit http://agr.wa.gov/PlantsInsects/InsectPests/GypsyMoth/.
