Spotted Wing Drosophila Update – August 19, 2022


Female Spotted Wing Drosophila
Female Spotted Wing Drosophila; photo by Christina Hillier

Spotted Wing Drosophila Alert:  8/19/2022


David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist, Phil Fanning, Assistant Professor of Agricultural Entomology


Spotted wing drosophila fly counts were over the recommended control threshold at all but one of our scouting locations this week. Numbers are generally rising, although we are still expecting an exponential growth of fly numbers in the coming days.  Sites over the six-fly threshold that is considered potentially damaging to ripening berry crops included Wells, Springvale, Limerick, New Gloucester, Bowdoinham, Mechanic Falls, Monmouth and Wayne. (see table below).  


Spotted Wing Drosophila Larva in Blackberry
SWD Larvae in Blackberry, photo by David Handley

Fall raspberries, blackberries and day neutral strawberries are now coming into harvest and will need to be protected. Growers should maintain a 5-7-day spray schedule once fly numbers have exceeded the threshold of 6 SWD flies in a trap per week, or larvae are noticed in the fruit. Look for fruit flies hovering around fruit and symptoms of premature fruit decay.


Keep berry fields clean of over ripe and rotten fruit as much as possible.  Rotten fruit on the plants or on the ground will greatly increase the number of fruit flies present, by providing them with food and egg-laying sites.   


For more information on identifying spotted wing drosophila (SWD) and updates on populations around the state, visit our SWD blog at:


Other IPM Web Pages
Michigan State University: 

Penn State University: 


David T. Handley
Vegetable and Small Fruit Specialist


Highmoor Farm Pest Management Office
P.O. Box 179 491 College Avenue
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 8/5/22 Spotted Wing  Drosophila weekly trap catch 8/12/22 Spotted Wing  Drosophila weekly trap catch 8/19/22
Wells 17 13 14
Springvale 1 5 42
Limerick 3 11 290
New Gloucester 18 84 39
Bowdoinham 52 574 24
Mechanic Falls 0 0 26
Monmouth 11 23 76
Fayette 0 3 4
Wayne 2 6 15