Spotted Wing Drosophila Alert — September 25, 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 were generally lower this week (see table below). However, trap counts at all sites are over threshold to prevent infestation, and all sites still require regular protective sprays on any fruit yet to be harvested. Larvae have been found in raspberry and highbush blueberry fruit samples collected from most remaining sites and are highest in plantings that are not presently being sprayed. All ripening fruit should continue to be protected with regular sprays to prevent infestation. Growers should maintain a 5-7-day spray schedule on remaining fruit to prevent infestation.
It is likely that the continued dry conditions, cooler night temperatures and shorter daylengths are beginning to slow spotted wing drosophila activity. However, experience tells us that the flies will continue be active as long as ripening fruit is available, even after frost. Therefore, we expect that protection of ripening fruit will be necessary 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 8/21/2026 | SWD weekly trap catch 8/28/2026 | SWD weekly trap catch 9/4/2026 | SWD weekly trap catch 9/11/2026 | SWD weekly trap catch 9/18/2026 | SWD weekly trap catch 9/25/2026 |
|---|---|---|---|---|---|---|
| Wells | 23 | 45 | 582 | 620 | 831 | 314 |
| Sanford | 29 | 127 | 3,024 | 3,232 | (traps pulled out, crops finished) | – |
| New Gloucester | 12 | 6 | 116 | 483 | (traps pulled out, crops finished) | – |
| Cape Elizabeth | 6 | 33 | 172 | 2,576 | 2,040 | 677 |
| Bowdoinham | 489 | 174 | 229 | 139 | 60 | 54 |
| Monmouth | 243 | 16 | 36 | 88 | 54 | 26 |
| Mechanic Falls | 78 raspberry
17 blueberry |
48 raspberry
111 blueberry |
749 raspberry
59 blueberry |
1,125 raspberry
688 blueberry |
981 raspberry
594 blueberry |
1,283 raspberry
169 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.