Spotted Wing Drosophila Update: August 13, 2021


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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 continued to rise in most locations this week. Although the increase was not as dramatic as last week, these population levels will enhance the threat of larvae infesting the fruit, unless it is protected regularly and often. Growers with ripe or nearly ripe berry fruit should continue to 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 flies around the fruit during harvest, or have found larvae in the fruit.


Spotted wing drosophila populations are very likely to continue increasing in the coming weeks as more flies are now present to lay eggs and more food is becoming available. Monitor the flies in the planting with traps, and check ripe fruit often for the presence of larvae. 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 7/25/21 Spotted Wing  Drosophila weekly trap catch 8/1/21 Spotted Wing  Drosophila weekly trap catch 8/8/21
Wells 39 57 82
Sanford 12 18 110
Limington 97 472 183
Limerick 1 4 46
New Gloucester 176 2664
Bowdoinham 121 472 600
Mechanic Falls 1 9 3
Monmouth 27 147 1504
Wayne 4 38 76


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