Spotted Wing Drosophila Update: October 15, 2021

Spotted Wing Drosophila UPDATE:  10/15/2021

Last Issue for 2021 Season

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


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

This will be the last issue of the Spotted Wing Drosophila Alert for the 2021 season.  We’d like to thank all the growers who allowed us to set up traps in their fields and the scouts who helped maintain them, including Brooke Martin and Lee Lavoie. Special thanks to Caitlin Ramsay for editing and mailing the newsletter and for updating our website and blog.


Gray Mold on Strawberries
Gray Mold on Strawberries; photo by James Dill


Spotted wing drosophila catches in vinegar/yeast traps continued to trend lower this week, although counts at all trap locations remain over the control threshold for fruiting fields. Harvest of fall berries is winding down, although the season has been extended by warm weather and no killing frosts. In addition to SWD, growers have had to battle fungal diseases, including Botrytis (gray mold) and anthracnose fruit rots, due to the frequent rain characteristic of this fall.  Protection of remaining fruit from SWD and fungal diseases will require regular applications of effective insecticides and fungicides. A three to five-day spray schedule should be adequate. Rotate the insecticide and fungicide products used (IRAC and FRAC numbers) used to maintain long term effectiveness.



There have been some questions about the effectiveness of applying “cleanup” insecticide sprays for SWD late in the fall, in hopes of reducing overwintering flies and infestations of next year’s berries. To date, research has not shown this to be an effective tactic. SWD does not overwinter in large numbers in berry fields, and infestations that occur come from populations moving in from outside the fields.


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 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 9/26/21 Spotted Wing  Drosophila weekly trap catch 10/3/21 Spotted Wing  Drosophila weekly trap catch 10/10/21
Wells 896 8,224 6,256
Limington 4,872 1,682 1,936
Limerick 2,672 1,480 122
New Gloucester 2,344 165 222
Bowdoinham 3,096 1,880 278
Mechanic Falls 215 25* 42
Monmouth 3,160** 1,344** 720**
Wayne 5,664 2,224 154

*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