David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist; Christina Howard, Produce Safety Professional


Drosophila Trap
Drosophila Trap, photo by David Handley

Spotted wing drosophila (SWD) fruit fly counts were very high in our traps this week. Warm dry weather, combined with adequate food (ripe fruit) has allowed populations to grow.  Now that we have started to have frosts, activity should begin to slow, as the food resources dwindle and the flies prepare to overwinter.  However, experience has shown that these flies will continue to infest late ripening fruit late into the season unless temperatures remain very cold. Any fruit remaining for harvest needs to be protected. A five to seven-day spray interval is recommended for ripening berry fields to prevent infestation of larvae in the fruit.


In addition to insecticide applications, best management practices include

  1. Keep fields free of waste fruit to reduce their attractiveness to flies.
  2. Sort fruit before putting it in storage to remove any soft berries.
  3. Chill all harvested fruit to 34 degrees Fahrenheit immediately after harvesting to halt development of any eggs or larvae.
  4. Rotate pesticide products used regularly to prevent the possible development of resistance.
Spotted Wing Drosophila Larvain in Raspberry
SWD Larvae in Raspberry, photo by David Handley



Current information on registered pesticides for managing SWD is available in the New England Small Fruit Management Guide.  The online version is free and can be viewed here


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

Spotted Wing Drosophila Larvae in Elderberries
Spotted Wing Drosophila Larvae in Elderberries, photo by David Handley

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 Unit
P.O. Box 179                            17 Godfrey Drive
Monmouth, ME 04259           Orono, ME 04473
207.933.2100                           1.800.287.0279


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.

The University of Maine is an equal opportunity/affirmative action institution.


Spotted Wing Drosophila Weekly Trap Captures in Yeast/Vinegar traps

Town Spotted Wing  Drosophila weekly trap catch 9/4/20 Spotted Wing  Drosophila weekly trap catch 9/11/20 Spotted Wing  Drosophila weekly trap catch 9/18/20
Wells 303 287 149
Limington 3720 2264 1968
Limerick 381 137 98
Cape Elizabeth 325* 1616 418
Bowdoinham 1704 776 2144
Mechanic Falls 840 1176 1104
Monmouth 1256 1400 1000
Wayne 1352 1584 2976

*Trap broken