Spotted Wing Drosophila Update: August 26, 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 remain high this week.

We have seen some dramatic increases in populations at sites where growers have stopped spraying because their harvest season has ended, but sites that are still being harvested are also seeing higher populations of flies.  High population levels like these increase the threat of larvae infesting the fruit, unless it is protected regularly and often.  Growers still harvesting fruit should continue to protect their crops against infestation. For many fields, a five-day spray interval may be needed to keep larvae from infesting fruit. A seven-day interval may be adequate if you’re not yet seeing any flies or noticing infested fruit.


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

We expect spotted wing drosophila populations to continue increasing in the coming weeks as more flies are present and more ripe and rotten fruit is now available. Continue to monitor the flies in the planting with traps, and check ripe fruit 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 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 8/8/21 Spotted Wing  Drosophila weekly trap catch 8/15/21 Spotted Wing  Drosophila weekly trap catch 8/22/21
Wells 82 256 472
Sanford 110 4168*
Limington 183 ** **
Limerick 46 223*
New Gloucester 2384 170
Bowdoinham 600 912 1304
Mechanic Falls 3 328*
Monmouth 1504 2304 1184
Wayne 76 1648*

*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