Spotted Wing Drosophila Update: September 3, 2021


Click on photos to enlarge.

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


Drosophila Trap
Drosophila Trap, photo by David Handley



Spotted wing drosophila catches in vinegar/yeast traps have reached the highest levels of the season  this week. We are seeing significant increases in populations at nearly all sites just as fall raspberries and day neutral strawberries are coming into season.  These high population levels increase the threat of larvae infesting the fruit, unless it is protected regularly and often. Some growers have moved to a three- to five-day spray interval to keep larvae out of fruit.  A five-day to seven-day interval may still be adequate if you have not yet seen many flies or noticed infested fruit.


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

Populations may continue to increase as the recent tropical storm could have brought up more flies from the south, and as more ripe fruit becomes available. Remember that keeping the fields as free as possible  from over ripe fruit and waste fruit on the ground can help reduce fly numbers.  Harvest fruit regularly and often, and chill any fruit that is going to market down to 32-38 degrees Fahrenheit, to stop the development of any eggs or larvae that may be present.


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


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David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management Unit
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 8/15/21 Spotted Wing  Drosophila weekly trap catch 8/22/21 Spotted Wing  Drosophila weekly trap catch 8/29/21
Wells 256 472 736
Limington ** ** 664
Limerick 223* 555
New Gloucester 2384 170 269
Bowdoinham 912 1304 913
Mechanic Falls 328* 288
Monmouth 2304 1184 1824
Wayne 1648* 3344

*Number represents 2 weeks of capture

**Trap damaged; no data


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