Spotted Wing Drosophila Alert — August 7, 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 remained relatively stable this week and at low levels where we are monitoring with vinegar/yeast traps in raspberries and highbush blueberries (see table below). Larvae have been found in raspberry and highbush blueberry fruit samples collected from five of these sites but at low concentrations. The highest counts were in plantings that are not presently being sprayed. Because of the presence of spotted wing drosophila flies in fields and some infested fruit, growers should maintain a spray program to prevent infestation. A 7-day spray schedule on ripening fruit has been adequate to prevent infestation to date. However, growers should consider tightening the spray schedule to every 5 days if larvae are found in harvested fruit.
Keeping the fruit fields free of overripe and rotten fruit can significantly reduce the presence of spotted wing drosophila in your fields. Encourage pickers not to leave fruit on the ground and clean out the planting of ripe fruit by harvesting frequently. Keep the area under the bushes free of weeds and excess growth that provides shelter, shade and moisture for the flies. Keeping good air movement in the planting to encourage dry conditions will discourage the flies.
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 |
|---|---|---|---|---|---|
| Wells | 9 | 2 | 2 | 1 | 2 |
| Sanford | (no data) | (no data) | 1 | 4 | 14 |
| New Gloucester | 2 | 65 | 9 | 16 | 49 |
| Cape Elizabeth | 3 | 1 | 1 | 0 | 0 |
| Bowdoinham | 0 | 78 | 40 | 27 | 20 |
| Monmouth | 0 | 0 | 1 | 0 | 3 |
| Mechanic Falls | (no data) | (no data) | 1 | 0 | 0 |
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