Spotted Wing Drosophila Alert — August 14, 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 continue to be at relatively low levels at most of our sites with vinegar/yeast traps in raspberries and highbush blueberries (see table below). However, one trap in Bowdoinham showed a significant jump in fly numbers. Larvae have been found in raspberry and highbush blueberry fruit samples collected from five of these sites but at low concentrations, except where plantings were not presently being sprayed. With the presence of spotted wing drosophila flies in fields and some infested fruit, all ripening fruit should be protected with regular sprays to prevent infestation. A 7-day spray schedule on ripening fruit has been adequate to prevent infestation to date. However, growers should tighten the spray interval to every 5 days if larvae are found in harvested fruit.
The increase in fruit fly populations that occurs when growers stop spraying illustrates the importance of keeping a regular spray schedule for any fields that are still being harvested, and keeping fields clean of over ripe fruit as much as possible. Populations of spotted wing drosophila will likely increase as more fruit becomes available, so it is important to keep monitoring flies and checking fruit for larvae, as well as maintaining 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
| 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 | SWD weekly trap catch 8/7/2026 | SWD weekly trap catch 8/14/2026 |
|---|---|---|---|---|---|---|
| Wells | 9 | 2 | 2 | 1 | 2 | 5 |
| Sanford | (no data) | (no data) | 1 | 4 | 14 | 8 |
| New Gloucester | 2 | 65 | 9 | 16 | 49 | 44 |
| Cape Elizabeth | 3 | 1 | 1 | 0 | 0 | 1 |
| Bowdoinham | 0 | 78 | 40 | 27 | 20 | 277 |
| Monmouth | 0 | 0 | 1 | 0 | 3 | 11 |
| Mechanic Falls | (no data) | (no data) | 1 | 0 | 0 | 1 |
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