Spotted Wing Drosophila Response Team helps Michigan growers manage the pest

Fly of East Asian origin has migrated to the United States and is infesting fruit crops causing losses for growers.

Spotted wing drosophila (SWD), an exotic vinegar fly of East Asian origin, was first found in southwestern Michigan in late fall 2010. In the western United States, it has already infested numerous fruit crops and caused economic losses to growers.

Unlike the native vinegar fly that is more of an annoyance than a problem, SWD, or Drosophila suzukii, is able to lay eggs in ripe fruit still on the plant, rather than in just overripe or rotting fruit. Populations of SWD can build quickly because there can be multiple generations per year and female flies (who live 20 to 30 days) can lay hundreds of eggs during their life spans. Michigan growers are prepared for this new pest because of the actions of the SWD Response Team, headed by Rufus Isaacs, Michigan State University (MSU) small fruit entomologist.

“In the fall of 2009, I attended a workshop in Oregon presented by research and Extension entomologists who talked about the pest, describing how bad it was for them to deal with,” Isaacs said. “From their presentations, it was clear that much of the eastern U.S. was at risk, and although Michigan’s cold winters might limit the pest, our summer climate and its host range looked appropriate enough to be concerned.”

Isaacs discussed what he’d learned about SWD with fellow MSU fruit entomologists and Extension specialists, highlighting the need for immediate attention. They decided to form the SWD Response Team, and get stakeholders – including the Michigan Department of Agriculture and Rural Development (MDARD), MSU Extension, industry representatives and others – on board. This group got together to decide how and where to monitor for SWD in 2010.

Twenty-eight counties were monitored for SWD in 2010, and none were found until the third week in September, which was after fruit harvest. SWD continued to be found in traps until late November.

“SWD was found in 13 of the counties monitored for the pest in 2010,” Isaacs said. “It was a warm fall season, which accounted for the finds so late in the year because SWD activity is predicated by the weather. But there was no economic impact on fruit.”

Once SWD was found, the SWD Response Team put out the word through the newly created SWD website and informational materials for Michigan growers, as well as presenting SWD information at grower meetings during the winter.

In 2011, the survey was widened, and, as of early December, SWD was found in nine more Michigan counties. During the year, the team studied trap designs and baits; examined the timing and activity of SWD activity; created an SWD detection survey database; conducted chemical control studies; held SWD workshops for growers, crop scouts, consultants and Extension personnel; presented information at grower meetings; published information in grower publications; and created Extension bulletins and a North Central Integrated Pest Management (NC-IPM) Center pest alert.

Though this pest has great potential to create economic losses, being forewarned means Michigan fruit growers are more prepared to deal with it.

“I’m optimistic,” said Isaacs. “Last year, we were facing a pest that we didn’t know much about. This year, growers have been learning more about it, and now know that it is another pest they will need to add to theirIPM (integrated pest management) program. There are pesticides that can be used to control it in the short term, and we will be exploring alternative control tactics. We now have a strategy to manage SWD that will improve as we learn more.

“The downside is that this pest is likely to make fruit farming more expensive for some growers because of the increased costs of production,” he noted.

The SWD Response Team has been “a fantastic example of what can be achieved when people come together to address a problem like this,” Isaacs added. “Researchers from multiple campus labs are linked with the Extension programs in the counties with tree fruit and small fruit growers. Increasing awareness and explaining the solutions has been a really great aspect of this team.”

Isaacs said that Extension educators are actively monitoring for SWD in their areas around the state. Work on SWD in Michigan has led to collaboration with research colleagues in other eastern U.S. states toward the development of strategies that can benefit the entire region, he noted.

“There is much we can learn from other regions, although we have some specific challenges here that MSU scientists are addressing as part of the response team,” Isaacs said.

For more information on SWD and Michigan’s SWD Response Team, go to Project GREEEN, the U.S. Department of Agriculture Specialty Crop Block Grant through MDARD, Michigan grower groups and the United States Environmental Protection Agency provide funding for the SWD Response Team and its activities.

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