Spotted Wing Drosophila Update: August 28, 2020


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


Spotted wing drosophila (SWD) fruit fly numbers rose again at most of our monitoring sites this week. This is partly due to more availability of waste fruit in some plantings.

Drosophila Trap
Drosophila Trap, photo by David Handley

However, another factor may be that: as fields get picked out of berries, i.e. food becomes more scarce late in the season, our trap bait becomes more attractive, and better at catching the flies. Even if this is so, the numbers are still high above control thresholds and any fruit still on the plants 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.


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

Although it’s difficult as we get towards the end of the season, keeping the field free of waste fruit can help keep drosophila numbers down. Sort fruit at harvest and before putting in storage to remove any soft berries. All fruit should be chilled to 34 degrees Fahrenheit immediately after harvest to halt development of any eggs or larvae. 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
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 8/14/20 Spotted Wing  Drosophila weekly trap catch 8/21/20 Spotted Wing  Drosophila weekly trap catch 8/28/20
Wells 36 107 250
Sanford 42 424 1408
Limington 1188 1480 4272
Limerick 114 594 992
Cape Elizabeth 101 3216 1816
Bowdoinham 2440 2920 1384
Mechanic Falls 95 351 408
Monmouth 2944 2480 3064
Wayne No data 920 1528