Spotted Wing Drosophila Update 9/10/2021

Spotted Wing Drosophila Update:  9/10/2021

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 Emerging from Fall Raspberries
SWD Emerging from Raspberries 3 Photo by JDill



Spotted wing drosophila catches in vinegar/yeast traps continue to be very high this week. Infestations are almost certainly occurring in any unprotected berries.  Significant increases in populations occurred in traps placed in unsprayed fields. Regular sprays will likely be needed for the remainder of the harvest season to protect against infested fruit. Most growers are using 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 will continue to increase as ripe and rotten fruit becomes available. Keeping 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 8/22/21 Spotted Wing  Drosophila weekly trap catch 8/29/21 Spotted Wing  Drosophila weekly trap catch 9/5/21
Wells 472 736 1,864
Limington ** 664 2,504
Limerick 223* 555 115
New Gloucester 170 269 224
Bowdoinham 1304 913 6,320
Mechanic Falls 328* 288 154
Monmouth 1184 1824 11,328**
Wayne 1648* 3344 85*

*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