Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.
Fruit Growers Alert – July 9, 2013
For full page print version, please see link at the bottom. Click on photos to enlarge.
SPOTTED WING DROSOPHILA HAS BEEN FOUND IN MAINE!
David Handley, Vegetable & Small Fruit Specialist; James Dill, Pest Management Specialist; Frank Drummond, Professor of Insect Ecology/Entomology
Male spotted wing drosophila flies were captured in traps in Dresden and Whitefield on July 3rd in wild blueberry fields. On Saturday, July 6th, a male fly was caught in a Winterport blueberry field. We have traps set out in raspberry and highbush blueberry fields in southern and central Maine, but have not yet captured any spotted wing drosophila in those fields. However, the presence of spotted wing drosophila in the wild blueberry fields indicates that this insect is now becoming active in the state, slightly earlier than our first captures last year. Research and Extension staff in Connecticut, Massachusetts, New Hampshire and New York have all reported captures of spotted wing drosophila over the past two weeks, although in all cases the numbers have been low.
- Photo by David Handley
- Photo by James Dill
|Raspberries before and after infestation, 48 hours at room temperature after picked.
Spotted wing drosophila (Drosophila suzukii) is a new pest which is a concern for raspberries blueberries and day neutral strawberries, as well as many other soft fruits. This insect is a small fruit fly, similar to the type that fly around the over-ripe bananas in your kitchen. However, this species will lay its eggs on fruit before it ripens, resulting in fruit that is contaminated with small white maggots just as it is ready to pick. As a result, the fruit quickly rots and has no shelf life. This insect first came into Maine in 2011, and caused significant losses in raspberry and blueberry plantings last year. Spotted wing drosophila can complete a generation in less than two weeks, with each adult female laying hundreds of eggs, so populations can explode rapidly when conditions are right. This makes them very difficult to control, and frequently repeated insecticide sprays (1 to 3 times per week) are often needed to prevent infestations once the insect is present in a field. It appears that spotted winged drosophila can successfully overwinter here, although it has not been able to build up to damaging levels until late summer. June-bearing strawberries and early ripening varieties of raspberries and blueberries may escape infestation, but later ripening varieties and everbearing types of strawberries and raspberries will likely become infested if they are not protected. Now that spotted wing drosophila has been confirmed in Maine, growers should 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 lb. 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 on the Penn State Extension 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
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