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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Spotted Wing Drosophila Getting Worse

This article was published originally on 8/9/2013

The spotted wing drosophila (SWD), Drosophila suzukii, named for the spot in the outer edge of the male's wing, is present in Iowa, though the extent is not known.  Nearby states to the east and north are reporting major problems with SWD larvae in fruit and adult fruit flies in apple-cider-vinegar-baited traps.  We have received one sample in Iowa so far this summer, a new county record from Chickasaw County.  Other samples shouldn't be too far behind.  The map below shows the reported incidence to date. 
 
SWD is especially troublesome for growers of blueberries, blackberries and raspberries.  The adult females saw through ripening, soft-skinned fruits to lay eggs.  Larvae inside quickly render the fruit unusable.  Monitoring to detect the adult flies is recommended, followed by insecticide applications to control the adult stage.  Sprays are problematic as the fruit are ripening.  Be careful to read and follow label directions concerning pre-harvest interval.  See the insecticide table below from Rick Weinzierl, University of Illinois.
 
Resources:
Spotted Wing Drosophila Now Present in Iowa 
Illinois Fruit & Vegetable News 
Michigan State University SWD Site 
SWD Pest Alert  
 
Short PHI (preharvest interval) insecticides effective against spotted wing drosophila. 

Insecticide PHI (days) in Blueberries PHI (days) in Brambles Days of Residual Activity*
Malathion 1 1 5-7
Imidan 3 Not labeled 7
Mustang Max 1 1 7
Danitol 3 3 7
Brigade 1 3 7
Delegate 3 1 7
Entrust (OMRI) 3 1 3-5
Pyganic (OMRI) (12 hours, REI) (12 hours, REI ) 2

 
*Estimates of residual activity are adapted from work done by Rufus Isaacs and reported on the Michigan State University web site listed above.
 
 
SWD males have a prominent spot in each wing.SWD males have a prominent spot in each wing.  Photo by Laura Jesse.