Spotted Wing Drosophila Update: 7/23/2021

Spotted Wing Drosophila Update:  July 23, 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


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

While we continue to find spotted wing drosophila fruit flies in raspberry plantings and blueberry fields in Maine this week, the situation has not changed much since last week. Counts of flies in vinegar/yeast traps remain in the three to ten range, meaning that growers should consider protecting ripening fruit to protect against infestation. When six to ten flies are caught in a yeast-baited trap in a week, larvae will start appearing in the fruit. A seven-day spray interval should be adequate at this point, but if growers are seeing drosophila flies around ripening fruit during harvest, or have found larvae in the fruit, they should tighten the spray schedule to every five days.  This was the situation at one raspberry field this week, as flies were readily visible while I was setting up a trap, and ripe fruit near the ground was soft and infested with larvae.

Expect spotted wing drosophila populations to increase in the coming weeks as more fruit becomes available. Set out traps, if you haven’t already, to monitor the flies. See last week’s SWD Alert 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…ies/spotted_wing_drosophila

University of New Hampshire


David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                      Pest Management Office
P.O. Box 179                           17 Godfrey Dr.
Monmouth, ME 04259           Orono, ME 04473
207.933.2100                          1.800.287.0279

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