Cooperative Extension at Highmoor Farm

Spotted Wing Drosophila Alert — September 18, 2026

David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist; Phil Fanning, Assistant Professor of Agricultural Entomology; Christina Howard, Maine New Farmers Project Manager

Spotted wing drosophila fruit fly numbers in raspberries and highbush blueberries were fairly stable this week after significant increases over the past two weeks (see table below). The numbers at all sites are still at, or close to, seasonal highs, and all require regular protective sprays on any fruit yet to be harvested to prevent infestation. Larvae have been found in raspberry and highbush blueberry fruit samples collected from all remaining sites but are highest in plantings that are not presently being sprayed. All ripening fruit should now be protected with regular sprays to prevent infestation. Growers should maintain a 5-day spray schedule on remaining fruit to prevent infestation.

Although cooler night temperatures and shorter daylengths will slow spotted wing drosophila activity, the flies will continue to be active as long as ripening fruit is available. Fruit ripening is also slower as temperatures cool but continue to harvest fields often to minimize the amount of susceptible fruit, and check harvested fruit for larvae. Chill harvested fruit immediately to increase shelf life.

For more information on identifying spotted wing drosophila (SWD) and updates on populations around the state, visit UMaine Highmoor Farm’s Spotted Wing Drosophila Alerts webpage.

Other IPM Web Pages
Michigan State University Spotted Wing Drosophila
Penn State University Spotted Wing Drosophila Overview
University of New Hampshire SWD Weekly IPM Reports

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm
P.O. Box 179
Monmouth, ME 04259
207.933.2100

UMaine Extension Diagnostic Research Lab
Pest Management Unit
17 Godfrey Drive
Orono, ME 04473
1.800.287.0279

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