Part of Methow Valley under apple maggot quarantine

The adult form of the apple maggot is a small fly with black bands on its wings.

TWISP, Wash. — Part of Okanogan County is being added to the state’s apple maggot quarantine in an effort to slow the spread of the invasive pest and protect commercial apple production.

The state Department of Agriculture is adding Methow Valley north of Gold Creek to the state’s quarantine starting Nov. 9. It prohibits people from moving homegrown or foraged fruit from the area and requires the county to keep green waste in the area separate from municipal waste.

Apple maggot has been detected in Methow Valley for several years but state surveys by the end of 2017 indicated a reproducing population and that triggered the action, said Jim Marra, pest program manager of the department’s plant protection division. Once on the list areas generally don’t come off.

“We think it came in from backyard fruit from Western Washington and spread among backyard fruit in the valley and hawthorn along river banks,” he said.

It has spread to four to six commercial orchards in the area and organic orchards tend to be more susceptible, he said.

The Okanogan County Pest Board has been using pesticides, cutting down trees and collecting fruit to try to control the spread but once an area is infested eradication is not viable, Marra said.

Apple maggot, also known as a railroad worm, is a pest of several fruits, mainly apple. It has long been active on the East Coast but was discovered in Portland in 1979. It’s been active in western Oregon and Washington and slowly spread east of the Cascades as a low-level problem in backyard fruit trees and has never been detected in commercially packed fruit.

The Department of Agriculture and Washington State Tree Fruit Association are concerned with keeping it that way.

Other quarantined areas are all of Western Washington, the western half of Chelan County, Kittitas County, the western and northern two thirds of Yakima County, Klickitat County, the southeastern portion of Lincoln County and Spokane County.

WSDA is still working on expanding its apple maggot quarantine rule to include potted soil of host plants. The idea is to prevent nurseries from shipping infected host plants and their potted soil into tree fruit regions of Eastern Washington. A Small Business Economic Impact Statement has yet to be completed before the rule can be amended.

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