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ARS Home » Pacific West Area » Wapato, Washington » Temperate Tree Fruit and Vegetable Research » Research » Research Project #443924

Research Project: Treatment Development for Apple Maggot Fly in Apples using Vacuum Steam Method

Location: Temperate Tree Fruit and Vegetable Research

Project Number: 2092-22430-003-056-I
Project Type: Interagency Reimbursable Agreement

Start Date: Jul 1, 2023
End Date: Jun 30, 2024

Apple maggot fly (Rhagoletis pomonella) is a major quarantine pest of apples with zero tolerance in the Pacific Northwest (PNW) of the US, where the value of fresh apples is valued at approximately $2 billion, with about 30 percent exported to foreign markets (NW Horticultural Council 2022). Apple maggot is found in low numbers within the major apple-growing regions in central Washington and is a continual threat to the export of apples. Washington State Department of Agriculture regulations state that when a fly is detected within a half mile of a commercial orchard, the orchard is threatened and apples harvested from it must undergo a cold treatment for at least 90 days at 37.9ºF (3.28ºC) or at least 40 days at 32ºF (0ºC) before shipment is allowed (WSDA 2022). The delay in shipment impacts the competitiveness of the growers and may reduce profits. A system to disinfest apples of apple maggot larvae in < 40 days would be of benefit for commercial apple growers in the PNW. Here, work is proposed for a treatment system that can kill apple maggot larvae in apples within 4 hours versus 40 days under the traditional cold treatment method. The objectives of this project are to determine: (1) If the steam heating system can kill 100% of apple maggot larvae in naturally-infested apples. (2) Whether the steam heat treatment affects basic quality measures of apples.

Apple-maggot infested apples will be collected under wild apple trees at sites in western Washington and transported to a site within the apple maggot quarantine area in central Washington. A vacuum steam treatment unit will be used to treat the infested apples. Apples will be treated for 2-4 h within the unit and then set on hardware cloth placed in bus tubs for larvae to emerge over a 2-month period. Untreated control apples will be held next to treated apples. Treated apples will also be measured for firmness and sugar values as basic quality measures.