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Spotted Wing Drosophila Alert: July 21, 2017

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Male and Female Spotted Wing Drosophila

Male and Female Spotted Wing Drosophila, image by Alan Kenage, Capital Press


Click on photos to enlarge.

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

There has been an increase in spotted wing drosophila activity at most trapping sites this week (see table below). Reports from throughout the northeast suggest a similar trend. This is significantly earlier activity than we have seen in recent years, and some of the trap counts are already well above what we consider potentially damaging to ripening berry crops, especially raspberries and blueberries.  Research suggests that when 6 to 10 flies are caught in a yeast-baited trap in a week, larvae will start appearing in the fruit.

We expect that spotted wing drosophila populations (SWD) will continue to build rapidly in the coming weeks as more eggs are laid in the fruit that is now ripening. Growers should set out traps, if you haven’t already. Start protective sprays on any berries that have begun to ripen when more than four spotted wing drosophila flies are caught in a trap, or any larvae are noticed in the fruit. Look for fruit flies hovering around fruit and symptoms of premature fruit decay. Remember, the flies favor shady, moist regions of the planting.

Insects in Spotted Wing Drosophila Trap

Insects in Spotted Wing Drosophila Trap, Male SWD Circled, photo by Kaytlin Woodman

You can find directions for making a home-made SWD monitoring trap on our SWD blog. An effective commercial trap and bait is now available from Scentry.  The trap is reusable and the bait lasts 4-6weeks.  Cost for both is about $15 plus shipping, it is available from Great Lakes IPM Company (

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 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 7/6/17 Spotted Wing  Drosophila weekly trap catch 7/13/17 Spotted Wing  Drosophila weekly trap catch 7/20/17
Wells 19 8
Sanford 0 4 6
Limington 4 2 7
Limerick 1 3 4
Cape Elizabeth 19 21 37
Buxton 12 6 3
New Gloucester 3 30 298
Bowdoinham 2 10 28
Dresden 0 0 2
Freeport 2 0 4
Poland Spring 1 2 2
Mechanic Falls 14 5 0
Monmouth 2 4 5
Wales 110 121
Farmington 0 3 9
Fayette 6 3 5





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