Spotted Wing Drosophila Alert: 9/17/2021

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

Spotted Wing Drosophila Alert:  9/17/2021

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




Spotted wing drosophila catches in vinegar/yeast traps are very high again this week, with some traps catching over 5,000 flies.  Therefore, larvae are almost certain to infest any unprotected berries still in the field.  Although evening temperatures have started to dip with the end of summer, spotted wing drosophila are known to be quite hardy and will remain active even after several frosts, as long as there is food available. Regular sprays are needed now throughout the season to prevent fruit from becoming infested. A three to five-day spray schedule should be adequate.  Rotate the insecticide products (IRAC number) used to maintain long term effectiveness.


Keep fields as free as possible from over ripe fruit and waste fruit on the ground to 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


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 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 8/29/21 Spotted Wing  Drosophila weekly trap catch 9/5/21 Spotted Wing  Drosophila weekly trap catch 9/12/21
Wells 736 1,864 1264
Limington 664 2,504 3440
Limerick 555 115 219
New Gloucester 269 224 371
Bowdoinham 913 6,320 5952
Mechanic Falls 288 154 236
Monmouth 1824 11,328** 13040**
Wayne 3344 85* 5482

*Trap damaged; limited data

**Unsprayed plot


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