Spotted Wing Drosophila Alert — August 27, 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 have risen at most of our sites over the past two weeks (see table below). Some, but not all, sites have stopped spraying and harvesting, which has likely resulted in fly numbers increasing, but there appears to be a general trend upwards in populations, as would be expected at this time in the season when more fruit is available. Larvae have been found in raspberry and highbush blueberry fruit samples collected from most of these sites but at low concentrations, except where plantings were not presently being sprayed. With the continued presence of spotted wing drosophila flies in fields and some infested fruit, all ripening fruit should be protected with regular sprays to prevent infestation. Growers should be maintaining a 5 to 7-day spray schedule on ripening fruit to prevent infestation.
Keep fields clean of over ripe fruit as much as possible. Populations of spotted wing drosophila will continue to increase as more fruit becomes available, especially over ripe fruit and fruit left on the ground. It is important to monitor flies in the field and check 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 | SWD weekly trap catch 8/21/2026 | SWD weekly trap catch 8/28/2026 |
|---|---|---|---|---|---|---|---|---|
| Wells | 9 | 2 | 2 | 1 | 2 | 5 | 23 | 45 |
| Sanford | (no data) | (no data) | 1 | 4 | 14 | 8 | 29 | 127 |
| New Gloucester | 2 | 65 | 9 | 16 | 49 | 44 | 12 | 6 |
| Cape Elizabeth | 3 | 1 | 1 | 0 | 0 | 1 | 6 | 33 |
| Bowdoinham | 0 | 78 | 40 | 27 | 20 | 277 | 489 | 174 |
| Monmouth | 0 | 0 | 1 | 0 | 3 | 11 | 243 | 16 |
| Mechanic Falls | (no data) | (no data) | 1 | 0 | 0 | 1 | 78 raspberry
17 blueberry |
48 raspberry
111 blueberry |
Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.
University of Maine Cooperative Extension is an equal opportunity institution and provider committed to nondiscrimination. For more information, visit extension.umaine.edu/nondiscrimination.