Spotted Wing Drosophila Alert:  9/15/2022

Spotted Wing Drosophila
Spotted Wing Drosophila, photo by Griffin Dill

David 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 remain high this week, with trap counts roughly similar to last week, although lower in locations where the spray schedule was recently tightened.  In the unsprayed site, numbers doubled this week, suggesting that fly populations are growing and the threat level to ripening fruit continues to be very high.  Growers should maintain a tight, regular (5-7 day) spray schedule to prevent larvae from infesting fruit. It is likely, based on past years’ data, that fly numbers will continue to climb as long as food is readily available, and the weather conditions remain good for their development.


Growers should maintain a 5-7-day spray schedule on all soft-fruited crops, including fall raspberries, blackberries, and day-neutral strawberries to prevent infestation by spotted wing drosophila larvae. Sprays should continue as long as flies are present and there is still fruit to harvest.


Spotted Wing Drosophila Larvae in Blueberry
Spotted Wing Drosophila Larvae in Blueberry; photo by David Handley

Once harvest starts, it can be difficult to keep berry fields clean of over-ripe and rotten fruit, but field sanitation has been shown to significantly reduce drosophila numbers, so it pays to keep waste fruit off of the ground as much as possible to reduce food and egg-laying sites.


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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Weekly spotted wing drosophila trap captures.

Town Spotted Wing  Drosophila weekly trap catch 9/2/22 Spotted Wing  Drosophila weekly trap catch 9/9/22 Spotted Wing  Drosophila weekly trap catch 9/16/22
Wells 647 1184 270
Limerick 20 202 34
New Gloucester 166 577 331
Bowdoinham 47 86 224
Mechanic Falls 249 992 623
Monmouth* 1,519 1032 3,088
Wayne 799 832 622

*Unsprayed plot