Spotted Wing Drosophila Alert — July 31, 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 remain relatively low and stable this week at the sites we are monitoring with vinegar/yeast traps in raspberries and highbush blueberries (see table below). We have found a few larvae in unsprayed raspberry fruit samples collected from two sites (Monmouth, New Gloucester) but these are very low concentrations. However, because of the continued low level presence of spotted wing drosophila flies in fields, growers should maintain a spray program to prevent infestation. A 7-10 day spray schedule on ripening fruit has been adequate to prevent infestation. Should populations increase as the season progresses, a 5-7 day spray interval may be needed to prevent infestation.
We expect spotted wing drosophila populations to build in the coming weeks, as more food sources become available. Protective sprays on any ripening berries should begin when more than four spotted wing drosophila flies are caught in a trap, or any larvae are noticed in the fruit. Look for fruit flies hovering around fruit and symptoms of premature fruit decay.
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
| Town | SWD weekly trap catch 7/7/2026 | SWD weekly trap catch 7/15/2026 | SWD weekly trap catch 7/24/2026 | SWD weekly trap catch 7/31/2026 |
|---|---|---|---|---|
| Wells | 9 | 2 | 2 | 1 |
| Sanford | (no data) | (no data) | 1 | 4 |
| New Gloucester | 2 | 65 | 9 | 16 |
| Cape Elizabeth | 3 | 1 | 1 | 0 |
| Bowdoinham | 0 | 78 | 40 | 27 |
| Monmouth | 0 | 0 | 1 | 0 |
| Mechanic Falls | (no data) | (no data) | 1 | 0 |
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