Spotted Wing Drosophila Update – August 5, 2022

Spotted Wing Drosophila on Raspberry
SWD on Raspberry; photo by David Handley.

 Spotted Wing Drosophila Update – 8/5/2022

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

Fly counts are creeping upwards this week but have not yet begun the rapid rise we typically see starting about this time.  Several sites, including Wells, Bowdoinham, New Gloucester, Monmouth, and Wells, were above the 6 fly threshold that is considered potentially damaging to ripening berry crops. At this level, growers should expect larvae to start appearing in the fruit unless protective sprays are applied (see table below).

Spotted Wing Drosophila Larvain in Raspberry
SWD Larvae in Raspberry, photo by David Handley

Spotted wing drosophila populations are expected to build rapidly in the coming weeks, especially if we get more rain. 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.

Keep berry fields clean of over-ripe and rotten fruit as much as possible. 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.

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 Spotted Wing Drosophila weekly trap catch 8/5/22
Wells 0 11 17
Springvale 0 0 1
Limerick 0 3 3
New Gloucester 4 11 18
Bowdoinham 10 14 52
Mechanic Falls 0 0 0
Monmouth 3 11 11
Fayette 0 0 0
Wayne 0 0 2