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Fruit Growers Alert 8/2/13: Spotted Wing Drosophila Populations Remain Low

Fruit Growers Alert – August 2, 2013

For full page print version, please see link at the bottom. Click on photo to enlarge.


Spotted wing drosophila (SWD) flies were captured in traps in Wells, Dresden, New Gloucester and Bowdoinham this week. Trap captures continue to be fairly low, with many locations not yet recording any flies.  We’re still seeing higher numbers near the coast and in the south, with nine flies caught in Dresden, six in New Gloucester and three in both Wells and Bowdoinham.

We have had several reports of maggots in blueberry fruit this week, but in each case the pest was blueberry fruit fly (aka blueberry maggot), not spotted wing drosophila.  Blueberry maggot is a common pest of blueberries in Maine and populations of this insect have been very high this season, according to Frank Drummond, Professor of Entomology at the University of Maine.

For a good fact sheet on this pest, visit our web site. If you are finding larvae in harvested blueberry fruit, there is a fact sheet on the North Carolina State University website to help identify which insect is causing the problem.

There is no valid threshold for spotted wing drosophila in berry fields.  At this point we believe that if any SWD have been captured in your area and you have ripe or nearly ripe fruit in your fields, the crop should be protected with a recommended insecticide.

Spotted wing drosophila poses the greatest threat to raspberries, blackberries, blueberries and other soft fruit that is beginning to ripen (elderberries, peaches, nectarines, etc.). Products that provide good control of drosophila on berries include Delegate®, Brigade®, Bifenture®, Danitol®, Mustang Max®, malathion and Assail®. Research carried out at the Connecticut Agricultural Experiment Station suggests that adding table sugar to group 4A insecticides such as Assail®, may improve their effectiveness. The recommended rate would be 1-2 lbs. sugar per 100 gallons of spray. Effectiveness of these products can range from three to seven days.  Repeated applications throughout the harvest season will likely be required to prevent larvae from infesting the fruit.  Please check product labels for rates, post-harvest intervals and safety precautions. Keeping the fields clean of over-ripe and rotten fruit can also help reduce the incidence of this insect.

For information on identifying spotted wing drosophila and making your own monitoring traps, visit the Michigan State University’s Spotted Wing Drosophila website.  There is also a good fact sheet series on Management of Spotted Wing Drosophila from Penn State on their website.

David T. Handley
Vegetable & 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

IPM Web Pages:

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.

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Image Description: Spotted Wing Drosophila Trap with One Male SWD Circled


University of Maine Cooperative Extension

Contact Information

Cooperative Extension at Highmoor Farm
52 U.S. Route 202
Monmouth, Maine 04259-0179
Phone: 207.933.2100
The University of Maine
Orono, Maine 04469
A Member of the University of Maine System