Spotted Wing Drosophila Alert — July 18, 2025
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
We are now catching spotted wing drosophila fruit flies at all of our trapping sites in Southern Maine (see table below) and wild blueberry fields in the coastal and midstate regions. Drosophila larvae have been reported in late ripening ripe strawberries, raspberries and blueberries in southern and central Maine, indicating that the flies are now actively laying eggs in ripening fruit.
If you are growing raspberries, blackberries and/or blueberries, You should be starting management practices now for spotted wing drosophila on any fruit that is ripening to prevent infestation.
Spotted wing drosophila populations are likely to build rapidly in the coming weeks as more food (fruit) becomes available for the flies. Start protective sprays on any berries that have begun to ripen 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.
We have found some maggots in blueberry fruit this week, but these are the larvae of Blueberry Fruit Fly (aka Blueberry Maggot), not spotted wing drosophila. Blueberry maggot populations of this insect have been very high this season, and any plantings that were not sprayed as fruit began to ripen are susceptible to infestation. For a good fact sheet on this pest visit our web site: http://umaine.edu/blueberries/factsheets/insects/201-monitoring-for-the-blueberry-maggot/
The larvae of these two pests can be distinguished from one and other based on shape and size. Blueberry maggot larvae are “carrot-shaped”. Their head end, with dark mouth parts often visible, is tapered to a point and their rear end, with six, light brown spiracles (breathing holes; in two rows of three) is flattened. Larvae of spotted wing drosophila are tapered on both ends, with their breathing tubes coming to a point at their rear end. Blueberry maggot larvae are also usually larger than drosophila larvae, but this is not always the case, depending on the stage of development of each.
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 6/27/25 | SWD weekly trap catch 7/11/25 | SWD weekly trap catch 7/18/25 |
|---|---|---|---|
| Wells | 0 | 4 | 9 |
| Springvale | 46 | ||
| New Gloucester | 0 | 14 | 42 |
| Cape Elizabeth | 0 | 56 | 101 |
| Bowdoinham | 0 | 8 | 43 |
| Mechanic Falls | 1 | 11 | 1 |
| Monmouth | 0 | 1 | 3 |
| Wayne | 0 | 3 | 1 |
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