Invasive fruit fly presence confirmed

The presence of an invasive insect that can damage berry crops has been detected and confirmed by researchers at the University of Minnesota and the Minnesota Department of Agriculture.

The Spotted Wing Drosophila flies have been found in Dakota, Rice and Ramsey counties. Unlike other fruit fly species, this one feeds on healthy, intact, ripening fruit, entomologist Mark Asplen said.

The real problem is you have this degradation of the fruit occurring on the inside that's not readily visible to growers," Asplen said. "Often times the damaged fruit is being picked and harvested, and the shelf life of that fruit is generally zero.

Raspberries, strawberries, grapes, blackberries, blueberries, cherries and plums are most susceptible to the flies, Asplen said. There's no known health risk associated with eating fruit infested with the flies, he said.

The pest could be present in other metro-area counties, as well Rochester and St. Cloud. Last year, researchers detected the flies in 29 Minnesota counties. Raspberries losses are estimated between $1 million and $1.5 million.

Spotted Wing Drosophila is a small fly, 2 to 3 millimeters in length, with a yellowish brown color and prominent red eyes. It was first detected in California in 2008, and then spread to the east coast by 2009 and the Midwest by 2010.

Researchers encourage growers and gardeners to use yeast-based or apple cider-based vinegar traps for early detection of adult flies; harvest fruit in a timely manner to avoid leaving over-ripe fruit on the ground; and use insecticidal sprays as needed.

A county map of the insects' activity is available at the MDA website, as well as the University of Minnesota's "VegEdge" Web page.