Drosophila Trap
Drosophila Trap, photo by David Handley


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


Spotted wing drosophila (SWD) fruit fly counts were variable from site to site this week, with some sites having lower numbers while others saw an increase. As colder weather arrives, numbers should start declining.  However, it is not until we have experienced repeated hard frosts that activity will stop, i.e.  not until the harvest season is finished.  So, populations are still high enough at all locations to cause significant infestation of any remaining berries.   A five to seven-day spray interval is recommended for any remaining fruit to prevent infestation of larvae.

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

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. 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


Other IPM Web Pages
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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 9/18/20 Spotted Wing  Drosophila weekly trap catch 9/25/20 Spotted Wing  Drosophila weekly trap catch 10/2/20
Wells 149 73 69
Limington 1968 907 1808
Limerick 98 51 40
Bowdoinham 2144 1520 356
Mechanic Falls 1104 45 87
Monmouth 1000 416 253
Wayne 2976 5548 262