The Oregon Department of Agriculture plans to spray an organic insecticide across thousands of acres of North Portland and Vancouver, Washington, over the next month to eradicate invasive gypsy moths.
The state found three Asian gypsy moths and two European gypsy moths in traps last year in North Portland and across the Columbia River in Vancouver. According to ODA spokesman Bruce Pokarney, the moths pose serious risks to trees and forests, and so far the state has managed to prevent them from taking hold.
“It’s a tremendous defoliator,” he said. “In the caterpillar stage, the moth eats leaves right off the trees. The Asian variety is of more concern to us because it has a wider appetite. It actually eats coniferous trees. And unlike the European gypsy moth, the female Asian gypsy moth flies. She can lay a bunch of eggs, get up and fly several miles and then lay some more eggs. So, you can see how that would lead to a much more rapid and widespread infestation if it’s not taken care of early.”
To kill the moths in their larval stage, the agency will spray a bacteria-based pesticide called Btk (Bacillus thuringiensis var. kurstaki) from helicopters over an 8,800-area area that covers part of Forest Park, the St. Johns neighborhood and West Hayden Island, as well as some land around the Port of Vancouver. The first of three applications is scheduled for early in the morning Saturday, April 16. The agency plans to complete the eradication effort by the end of May.
Pokarney said the spray area is mostly industrial land and forest, but it includes about 4,000 residents in the St. Johns neighborhood. Agriculture officials are advising people to consider staying indoors before and for about a half-hour after the treatment. The state has used Btk for the same purpose in Portland and Eugene in the past, Pokarney said, and there have been no documented human health impacts.
“Btk has a very excellent and safe track record,” he said. “We’re very aware that people have concerns about it, which is why we are providing as much information as possible. It is considered very low risk for human health. It’s very targeted to caterpillars.”
While Btk is not considered poisonous to people, Pokarney said, people who feel sick from exposure can call the Oregon Poison Center at 1-800-222-1222 for medical advice, and people who are immunocompromised or have serious food allergies may want to leave the spray area during the application.
ODA has an online sign-up sheet for people who would like to receive text messages or phone calls about when spraying will occur. Residents can get pre-recorded information about the status of the project by dialing 211. ODA will also provide timely information on Twitter.
“Just as a precaution, I would think people wouldn’t want to have direct exposure to the spraying as it happens,” Pokarney said. “But certainly in the years of experience we’ve had with this we have not seen widespread illness. We really have not seen an impact on human health through the use of Btk.”
Aimee Code of the insect conservation group the Xerxes Society said her group doesn’t oppose the spraying because the risks of a gypsy moth invasion are high, but there isn’t a high risk of the spraying affecting other species. Many insects won’t reach their larval stages until after the gypsy moth spraying is done, she said.
“The reality is the Asian gypsy moth is concerning, and the Department of Agriculture has been pretty smart about honing in on where the problem is and finding the least toxic option to manage it,” she said. “Our concern would be this becomes too commonplace, and in that case we would become concerned about butterflies and other moth species.”
The Washington Department of Agriculture also plans to spray for the moths in several locations across Washington, including Seattle, Tacoma, Kent, Gig Harbor and Lacey in May.