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Apple Maggot Survey Update

Summarized by Tianna DuPont, WSU Extension. Reviewed by Mike Bush and Bill Walker, WSDA June 20, 2022

The Washington State Department of Agriculture conducts an annual apple maggot survey to determine areas of Washington State that meet the official Pest-free area designation. Apple maggot has never been detected in commercially packed Washington fruit, and this program is critical to protect trade agreements. The following is a summary of the 2021 annual report for Washington from the WSDA. For the complete report visit download.

Apple maggot fly and pupae finds

In 2021 numbers of verified apple maggot flies in traps in major fruit growing counties monitored by the WSDA were Chelan County 30, Kittitas County 73, Okanogan County 693 (non-quarantined) and 4 (quarantined), Walla Wall 2, and Yakima County (quarantined area) 16. The WSDA also collect fruit (hawthorn) from trap sites in pest free areas that had positive apple maggot fly detections. Numbers of pupae obtained from fruit in 2021 were Chelan 2 and Okanogan 154. Currently pupae from fruit are in cold storage to induce overwintering behavior. When flies emerge in late spring to early summer they can be identified to species. Pupae reported are considered suspect until verification after emergence.

In comparison in 2020 in Okanogan County there were 471 positives for apple maggot adult flies in 281 traps monitored by the WSDA and in 2020 fruit from areas surrounding positive adult trap catches yielded 385 pupae several of which emerged and where confirmed as apple maggot by USDA-ARS. In 2019 120 apple maggot adult flies were caught in the pest free area of Okanogan County, however fruit collected from the surrounding area had zero finds for apple maggot pupae or larvae.

Quarantine status

In Okanogan County the WSDA worked with the Apple Maggot Working Group to form a sub-committee that includes area expertise to study the data and provide future quarantine options for the committee. The Okanogan County Pest board is actively involved in control at all active sites. The committee is currently looking at alternatives to quarantine. As of November 2018 a small section of Okanogan County was added to the quarantine region. Areas of Yakima, Klickitat, Kittitas and Chelan County have been under a quarantine for multiple years.

What triggers a quarantine?

The apple maggot survey is conducted by WSDA at the request of the tree fruit industry and entirely funded by self-imposed industry fees that provide the needed personnel, equipment and supplies for the agency to carry out the survey. Apple maggot survey data collected during the growing season is analyzed by the agency by the late fall and reported out to the Apple Maggot Working Group (AMWG).  Depending on survey results, the AMWG convenes in late fall or early winter to review the results and solicit input on those results from industry stakeholders, local governments, researchers, agency staff and the public.  During these meetings the agency also presents budget information and suggested future survey plans and staffing needs to accomplish those plans. The AMWG provides feedback and direction on future survey plans to meet the needs of the tree fruit industry. If a survey detects a reproducing population of apple maggot (typically evidenced by pupae reared from infested fruit) in a pest-free area then a conversation is initiated between the agency and the AMWG.  While the presence of a reproducing apple maggot population (typically indicated by pupae reared from fruit) often leads to a new or expanded quarantine area, this is not an automatic outcome. Quarantines are established through the rulemaking process which includes public notification, public comment and typically a small business economic impact assessment.  WSDA does not initiate rulemaking unilaterally and only conducts apple maggot quarantine rulemaking at the request of the tree fruit industry.  WSDA is not currently engaged in rulemaking on this subject and has not received a request from the industry to initiate rulemaking. This process typically takes a minimum of 5 months from the point at which a rulemaking is requested. A start date will be designated at the point that the rule is confirmed. The overall goal of any apple maggot quarantine is to protect pest-free areas of production while satisfying trade partners that apple maggot is under official control in the state.

What does a quarantine mean for growers and packers in an affected region?

Orchards with fruit grown in a quarantine area and within 1/2 mile of a positive trap catch are considered threatened and the fruit must be inspected or cold treated to ship from an area under quarantine to (or through) a pest free area in Washington.

  • A permit for movement is needed to ship fruit from an area under quarantine to (or through) a pest free area in WA. The shipment of fresh fruit must be accompanied by a permit for movement of fruit issued by the department verifying one of the following:
    • (a) The fresh fruit came from orchards and production sites that are not threatened (NOT within ½ mile of a positive trap) with infestation; or
    • (b) The fruit has been inspected and found free of apple maggot
      • All fresh fruit, as specified in WAC 16-470-111(1), from an orchard or production site that is infested or threatened with infestation by apple maggot must be inspected by the department following accepted agency standards.
      • If the fresh fruit is found to be infested with apple maggot it must be cold treated (90 days at 37.9 F or less.)
    • (c) The fruit has undergone cold treatment (90 days at 37.9 F or less.) WAC 16-470-113
  • Below is a list of countries that have restrictions or require treatment of Apples produced within an Apple Maggot Quarantined Area
    • Canada: Cold Treatment
    • Indonesia: In transit Cold Treatment or Fumigation
    • China: Cold Treatment or ALPP Trapping
    • Dominican Republic: MAY NOT SHIP
    • Israel: Cold Treatment
    • European Union: Systems Approach AM Trapping, Inspection or Cold Treatment
    • Sri Lanka: Treatment Details on Import Permit
    • Vietnam Some Import Permits Presented Require Cold Treatment

Additional Resources

WSDA Searchable map of quarantine designation

Administrative codes related to apple maggot are listed here

WSU Apple Maggot Webpage

Tri-County Pest Board Will Carpenter Will.Carpenter@CO.CHELAN.WA.US



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