Spotted Wing Drosophila Update: 10/1/2021

Spotted Wing Drosophila Update: 10/1/2021

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 Larvain in Raspberry
SWD Larvae in Raspberry, photo by David Handley


Spotted wing drosophila catches in vinegar/yeast traps remain very high, with most still having fly counts in the thousands this week. Although colder fall temperatures have begun to set in, we have seen in past seasons that this does little to slow spotted wing drosophila activity in fruiting fields.  It is not until food supplies (berries) are depleted and very cold temperatures arrive that the population will undergo significant decline.  So, regular sprays continue to be needed to prevent remaining fruit in the field from becoming infested.



Spotted Wing Drosophila Larvae in Blueberry
Spotted Wing Drosophila Larvae in Blueberry; photo by David Handley

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
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 9/12/21 Spotted Wing  Drosophila weekly trap catch 9/19/21 Spotted Wing  Drosophila weekly trap catch 9/26/21
Wells 1,264 4,560 896
Limington 3,440 3,984 4,872
Limerick 219 2,232 2,672
New Gloucester 371 2,440 2,344
Bowdoinham 5,952 3,336 3,096
Mechanic Falls 236 208 215
Monmouth 13,040** 5,336 3,160
Wayne 5,482 7,392 5,664

*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