New economic research reveals high cost of invasive species for Minnesota-grown raspberries
ST. PAUL – Minnesota raspberry growers lost an estimated $2.3 million in sales to the invasive fruit fly known as spotted wing drosophila in the 2017 season. Researchers funded by the Minnesota Invasive Terrestrial Plants & Pests Center (MITPPC) used local grower surveys in combination with field research and USDA census data to evaluate the economic impact of the state raspberry industry’s most significant pest. Their findings were recently published in the Journal of Integrated Pest Management.
The team’s electronic survey of 45 raspberry growers included questions about farming practices, spotted wing drosophila infestation rates, yield losses and plans for the future.
The survey found:
raspberry growers reported the highest levels of spotted wing drosophila infestation among the state’s fruit growers, with yield losses ranging from 2 to 100 percent and a median of 20 percent;
74 percent of raspberry growers surveyed reported actively managing to control spotted wing drosophila;
24 percent of raspberry growers surveyed said they would ‘probably’ or ‘definitely’ reduce acreage the following season as a result of spotted wing drosophila infestation
In 2017, the Twin Cities metro was named the raspberry consumption capital of America – households reportedly ate 132 percent more fresh raspberries than the national average.
According to the study, Minnesota produced roughly 2 million pounds of raspberries each season prior to detection of the invasive spotted wing drosophila.
“By our calculations, Minnesotans would readily consume more than 3.5 million pounds of ‘locally-grown’ raspberries worth nearly $24 million each season,” said study lead Gigi DiGiacomo, research fellow in the Department of Applied Economics. “Spotted wing drosophila is holding Minnesota raspberry growers back by limiting their ability to capture local consumer demand.”
DiGiacomo is working alongside faculty members from the departments of horticultural science and entomology to deliver new pest management techniques and economic decision-making tools to fruit growers facing this challenging pest.
“This research suggests that Minnesota berry growers, suppliers and retailers would benefit economically from a significant investment in spotted wing drosophila control strategies,” said DiGiacomo.
To control fly populations, 55 percent of surveyed non-organic growers practiced increased harvest frequency, 41 percent practiced field sanitation and 36 percent thinned plants. Organic grower numbers ranked similarly with 40 percent, 30 percent and 10 percent, respectively.
Mary Rogers, one of the study’s co-authors and assistant professor in the Department of Horticultural Science, is examining the efficacy of several alternative organic pesticides, along with the use of exclusion netting in high tunnel systems.
“At this point in time, our research suggests that exclusion with fine mesh netting on high tunnels may be one way for growers to reduce spotted wing drosophila pressure and delay infestation, particularly in fall-bearing raspberries,” said Rogers.
This study was funded by the MITPPC through the Environment and Natural Resources Trust Fund, with additional support from the UMN Extension IPM Program.