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Fruit Growers Alert 7/19/13: Spotted Wing Drosophila Counts are Rising

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Fruit Growers Alert – July 19, 2013

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


Spotted wing drosophila flies were captured in traps in Warren (6 males, 3 females) and Wells (2 females) this week in a strawberry field and raspberry field, respectively. These trap captures indicate that this insect is becoming more active in Maine. Last week we had low numbers caught in wild blueberry fields in Winterport, Whitefield and Dresden. Although the numbers are still quite low, and don’t pose an immediate threat to berry crops, populations are expected to increase in the coming weeks to damaging levels.  Research and Extension staff in Connecticut, Massachusetts, New Hampshire and New York are all reporting increasing numbers of spotted wing drosophila in traps over the past week, and one grower in Massachusetts claims to have found larvae in recently harvested fruit, although this is unconfirmed.

Spotted Wing Drosophila Larvae in Raspberry

Spotted Wing Drosophila Larvae in Raspberry, photo by David Handley

Spotted Wing Drosophila Larvae in Blueberry

Spotted Wing Drosophila Larvae in Blueberry, photo by David Handley

At this point in the season, spotted wing drosophila will pose the greatest threat to raspberries, blueberries and any other soft fruit that is beginning to ripen. They are able to lay eggs in fruit as soon as it starts to color. Spotted wing drosophila can complete a generation in less than two weeks and, with each adult female laying hundreds of eggs, populations can explode rapidly when conditions are right. Last year populations did not reach damaging levels until late August, but weather conditions can alter how quickly the flies will build up. Frequently repeated insecticide sprays (1 to 3 times per week) may be needed to prevent infestations once the insect is present in a field. Growers should now be on the alert and look for fruit flies on their fruit and symptoms of premature fruit decay. 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. 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.

Highmoor Farm Field Day
Please join us for the Highmoor Farm Field Day and Summer Tour to be held on Wednesday, July 31, starting at 9:00 a.m. Growers will have an opportunity to tour the fruit and vegetable research plots at the farm, part of the Maine Agricultural and Forest Experiment Station, and hear Extension specialists and guest speakers discuss current research on apples, grapes and vegetables. Maine State Legislators will also be on hand to offer updates on programs and legislation effecting farming in Maine.  Please join us for the program, farm tours and lunch. Visit the Field Day website for more information.

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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