Spotted Wing Drosophila Update: July 29, 2022

Male Spotted Wing Drosophila
Male Spotted Wing Drosophila, photo by Michigan State University

The University of Maine Cooperative Extension

Spotted Wing Drosophila Update:  7/29/2022

David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist, Phil Fanning, Assistant Professor of Agricultural Entomology


Fly counts this week remain at relatively low levels, but at several sites including Bowdoinham, New Gloucester, Monmouth, and Wells, the counts were just above the 6 fly threshold that is considered potentially damaging to ripening berry crops, especially raspberries and blueberries. At this level, growers should expect larvae to start appearing in the fruit unless protective sprays are applied (see table below).

Drosophila Trap
Drosophila Trap, photo by David Handley

We expect that spotted wing drosophila populations will build rapidly in the coming weeks as more food becomes available for the flies, especially if conditions remain warm and we get more rain. Growers are advised to set out SWD traps if you haven’t already. Start protective sprays on any berries that have begun to ripen, when more than six 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.

As harvest begins, it is important to try to keep the field clean of over-ripe and rotten fruit as much as possible.  Having lots of rotten fruit on the plants or on the ground will greatly increase the number of fruit flies present, by providing them with 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:

University of New Hampshire:


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 Spotted Wing  Drosophila weekly trap catch 7/18/22 Spotted Wing  Drosophila weekly trap catch 7/28/22
Wells 0 11
Springvale 0 0
Limerick 0 3
New Gloucester 4 11
Bowdoinham 10 14
Mechanic Falls 0 0
Monmouth 3 11
Fayette 0 0
Wayne 0 0