Cooperative Extension at Highmoor Farm

Spotted Wing Drosophila Alert — September 4, 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 continue to rise at our monitoring sites over these two weeks (see table below). The highest populations are being found at sites that have stopped spraying and harvesting, but there is a noticeable upward trend in populations, as is typical late in the season. Also noticeable is the appearance of more robust female flies, which we see when the overwintering generation of flies begins to appear. Larvae have been found in raspberry and highbush blueberry fruit samples collected from some sites, and in higher numbers, but mostly in plantings that are not presently being sprayed. With the increasing presence of spotted wing drosophila flies in fields and larvae infesting fruit, all ripening fruit should now be protected with regular sprays to prevent infestation. Growers should maintain a 5 to 7-day spray schedule on ripening fruit to prevent infestation.

Populations of spotted wing drosophila will continue to increase as more overripe and waste fruit becomes available. Keep checking fruit for larvae and maintain a regular spray schedule for the remainder of the season.

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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