Spotted Wing Drosophila Update August 6, 2021

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


Click on photos to enlarge.

Spotted Wing Drosophila Alert:  8/6/2021

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


Counts of spotted wing drosophila in vinegar/yeast traps have risen significantly this week. All trap locations saw increases of 2 to 15 times last week’s levels (see table below).  Reports from wild blueberry fields in Downeast  show similar jumps.  Growers with ripe or nearly ripe berry fruit should protect their crops against infestation. A five to seven-day spray interval should be adequate for keeping larvae out of fruit. Use a seven-day interval if you’re not yet seeing any flies or noticing infested fruit, but tighten to a five-day schedule if you see drosophila flies around ripening fruit during harvest, or have found larvae in the fruit.


Expect spotted wing drosophila populations to continue to increase in the coming weeks as more fruit, especially waste fruit, becomes available. Set out traps, if you haven’t already, to monitor the flies. See our blog for information on making and placing traps, and a list of currently registered insecticides for SWD.


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 Office
P.O. Box 179                               17 Godfrey Dr.
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 7/18/21 Spotted Wing  Drosophila weekly trap catch 7/25/21 Spotted Wing  Drosophila weekly trap catch 8/1/21
Wells 39 57
Sanford 12 18
Limington 97 472
Limerick 1 4
New Gloucester 176 2664
Bowdoinham 14 121 472
Mechanic Falls 1 9
Monmouth 1 27 147
Wayne 4 38


Characteristics of Insecticides for Spotted Wing Drosophila Control

Trade Name IRAC Group Days to Harvest
Days of Residual
Assail® 4A 1 5-7
Mustang Max® 3 1 7
Bifenture® 3 1 (3 raspberry) 7
Brigade® 3 1 (3 raspberry) 7
Danitol® 3 3 7
Delegate® 5 3 (1 raspberry) 7
Entrust®* 5 3 (1 raspberry) 3-5
Exirel® 28 3 (1 raspberry) 5-7
Imidan® 1B 3 (not for raspberry) 5-7
Malathion 1B 1 3-5
PyGanic®* 3A 0 0
Verdepryn ® 28 1 5-7


*OMRI approved