Spotted Wing Drosophila Update: August 16, 2019

Male Spotted Wing Drosophila
Male Spotted Wing Drosophila; photo by Griffin Dill. Actual size: 2-3 mm.


Click on photos to enlarge.

David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist; Frank Drummond, Professor of Insect Ecology/Entomology; Christina Howard, Produce Safety Professional

Spotted wing drosophila fruit fly numbers remained high at the berry farm locations where they have been over threshold for the past two weeks. While a few spots still have relatively low counts, this may be due to trap placement and/or regular pesticide applications, rather than a scarcity of flies at these locations. Susceptible crops, including raspberries, blackberries, blueberries and fall strawberries should remain on a protective spray schedule if ripening fruit is present. A seven-day spray interval should be adequate in most situations, but if larvae continue to be present in fruit with this interval, growers should shift to a five-day spray interval. Be sure to read and follow all pesticide product labels carefully, especially in regards to days to harvest restrictions and the number of applications allowed per growing season. Try to rotate products used regularly to prevent the possible development of resistance.

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

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                      UMaine Extension Diagnostic Research Lab
P.O. Box 179                           Pest Management Unit
52 U.S. Route 202                  17 Godfrey Drive
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.


Town Spotted Wing Drosophila weekly trap catch 8/2/19 Spotted Wing Drosophila weekly trap catch 8/9/19 Spotted Wing Drosophila weekly trap catch 8/16/19
Sanford 2 47 143
Limington 144 364 226
Limerick 0 9 4
Cape Elizabeth 73 211 318
Dresden 0 2 15
Buxton 14 37 352
Bowdoinham 62 82 108
Poland Spring 0 29 61
Mechanic Falls 1 4 0
Monmouth* 39 126 389
Fayette 1 1 2
Freeport 12 18 7
Farmington 10 42 2
Wayne 17 7 12
Wells 4 15 5

*unsprayed planting