Spotted Wing Drosophila Alert — July 15, 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 have increased significantly at some of the sights we are monitoring with vinegar/yeast traps in raspberries and highbush blueberries this week (see table below). We have not yet found Drosophila larvae in raspberry or blueberry fruit being harvested, and most growers have initiated a spray program to prevent infestation. At this point, a 7-10 day spray schedule on ripening fruit should be adequate to prevent infestation, but as populations increase, a 5-7 day spray interval may be needed to prevent infestation. Finding flies in numbers greater than four per week in these traps indicates that this pest is now actively laying eggs in developing berries, potentially causing significant reductions in marketable yield.
We expect spotted wing drosophila populations to build rapidly in the coming weeks as more ripe fruit becomes available, especially if weather conditions continue to be warm and damp. Now is the time to set out your own traps, if you haven’t already. 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.
A reminder: products that provide good control of drosophila on berry crops include spinosad (Radiant® for strawberries, Delegate® for raspberries and blueberries), Asana®, Brigade®, Danitol®, Exirel® and Assail®. Research suggests that adding table sugar to group 4A insecticides, such as Assail®, may improve their effectiveness. The recommended rate would be 1-2 lbs. sugar per 100 gallons of spray. Also, it is recommended to add 4-16 oz Nu Film P®/100 gal with all materials to improve SWD efficacy and, if it rains after you spray, re-apply a pesticide material. (Read the label for any re-application restrictions of the same material.) Please check product labels for rates, post-harvest intervals and safety precautions.
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 |
|---|---|---|
| Wells | 9 | 2 |
| New Gloucester | 2 | 65 |
| Cape Elizabeth | 3 | 1 |
| Bowdoinham | 0 | 78 |
| Monmouth | 0 | 0 |
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.