Spotted Wing Drosophila Alert: 10/7/2022

girl holds up a giant strawberryDavid Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist, Phil Fanning, Assistant Professor of Agricultural Entomology, Christina Howard, New Farmers Program Manager

Spotted wing drosophila fly counts have again dropped at nearly all sites this week.  One site in Limington is now below the spray threshold of six flies per trap per week.  This is the first time populations have been this low at this point in the season since we started statewide trapping in 2012.  However, the numbers are still high enough at most sites enough to infest late-ripening fruit. Fly numbers could increase in the coming weeks, although recent frosts are bringing an end to the harvest season at some farms.

A 5-7-day spray schedule is recommended on all soft-fruited crops, including fall raspberries, blackberries, and day-neutral strawberries, where populations exceed the threshold of more than six flies caught in a week. Removing rotten fruit from the fields that are still being harvested can significantly reduce drosophila numbers, so keep waste fruit off the ground as much as possible.

Male and Female Spotted Wing Drosophila Flies
Male (left) and Female (right) Spotted Wing Drosophila; photo by Griffin Dill. Actual size: 2-3 mm.

For more information on identifying spotted wing drosophila (SWD) and updates on populations around the state, visit our SWD blog at:

Other IPM Web Pages
Michigan State University:

Penn State University:

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                        Pest Management Office
P.O. Box 179                              491 College Avenue
Monmouth, ME 04259            Orono, ME 04473
207.933.2100                            1.800.287.0279

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Town SWD weekly trap catch 9/16/22 SWD weekly trap catch 9/23/22 SWD weekly trap catch 9/30/22 SWD weekly trap catch 10/6/22
Wells 270 214 44 14
Limerick 34 13 7 3
New Gloucester 331 227 29 53
Bowdoinham 224 292 74 57
Mechanic Falls 623 1,208 108 62
Monmouth* 3,088 1,320 790 614
Wayne 622 721 77 39

Weekly spotted wing drosophila trap captures.

*Unsprayed plot