An invasive fruit fly is threatening berry crops in Minnesota and forcing many growers to either change their techniques or get out of the business.

Spotted wing drosophila (SWD) primarily attacks raspberries, blackberries and blueberries but can also infest strawberries, grapes and stone fruit, according to the University of Minnesota Extension. 

"Its affected our raspberries, our strawberries, our grape tomatoes," said Paul Nelson with the Vegetable Farm in Montrose.

Nelson said they spend more hours keeping their high tunnels clean--picking up berries that have naturally fallen to the ground--to help stop the spread of SWD. 

"Without spraying at all, your berries will become infected quite rapidly," Nelson said. "So as much as we dont like to spray, we do need to spray to control this pest."

According to Bill Hutchison, a UMN professor of entomology and extension entomologist, about 20 percent of the states growers have either had to suspend berry production or have gone out of business because of SWD.

UMN researchers have been working with a vineyard near Hastings on how to control SWD. This summer, they used exclusion netting on wine grapes.

"Exclusion netting is just a fine-mesh netting thats small enough to exclude SWD from getting in but it still allows... the climate to stay the same for the crop its covering," said Dominique Ebbenga, a first-year masters student.

After reviewing some preliminary data, Ebbenga said, "We have some promising results showing that exclusion netting is excluding SWD."

Hutchison added, "It can literally completely eliminate the need for insecticides or greatly reduce it."