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Fruit Growers Alert 8/30/13: Spotted Wing Drosophila Continues to Spread

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Fruit Growers Alert – August 30, 2013

Click on photos to enlarge.


All sites that we are monitoring in southern and coastal Maine now have spotted wing drosophila flies and fly counts have increased at some sites this week.  We also have more reports from growers of larvae in fruit, indicating that that even low trap captures signal a significant threat.  Spotted wing drosophila (SWD) flies were captured in traps in Wells, Cape Elizabeth, Limington, Springvale, New Gloucester, Gray, Mechanic Falls, Monmouth, Wales, Livermore Falls, Farmington, Oxford, Bowdoinham, Dresden, Warren, Stillwater and Levant.  Trap captures continue to be very variable, ranging from just one fly to nearly 200, with most still catching fewer than 100 per week.  The coastal sites tend to have more flies than any other locations, but counts have been up and down from week to week at many sites. We expect fly populations to rise further in the coming days and weeks.  If you haven’t yet done so, we recommend that growers set up their own traps to monitor for SWD, and learn to distinguish it from other species that will get into the trap.  We recommend that all ripening fruit be protected with an approved insecticide. Regular and repeated treatments are needed to keep fruit from becoming infested. In some locations a 7-day spray interval has not been adequate to prevent infestation, so we have tightened the spray schedule to every 4 to 5 days. Chilling fruit to as close to 32ºF immediately after harvest can significantly reduce the activity and emergence of any larvae.  Keeping the fields clean of over-ripe and rotten fruit can also help reduce the incidence of this insect.

Fall Raspberries

photo by David Handley

Spotted Wing Drosophila Emerging from Fall Raspberries

photo by James Dill

Raspberries before and after infestation, 48 hours at room temperature after picked.

Recommended insecticide products that provide good control of drosophila on berries include Delegate®, Brigade®, Bifenture®, Danitol®, Mustang Max®, malathion and Assail®.  Effectiveness of these products can range from three to seven days.  Please check product labels for rates, post-harvest intervals and safety precautions.

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

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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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