 The states of Oregon, California, Idaho, and Utah, all areas of the eastern United States, and all "foreign countries where apple maggot is established" have also been placed under quarantine by Washington.In addition to these areas, as of 2017, all or portions of the state's counties of Chelan, Clallam, Clark, Cowlitz, Grays Harbor, Island, Jefferson, King, Kitsap, Klickitat, Lewis, Lincoln, Mason, Pacific, Pierce, Snohomish, Spokane, Skagit, Skamania, Thurston, Wahkiakum, Whatcom, and Yakima, are also quarantined.Washington State University's Tree Fruit Research and Extension Center has cited the fact that "apple maggots have never been found in commercially packed fruit in the state" as evidence of the quarantine's efficacy.