Michigan spotted wing Drosophila report for July 16, 2013

Spotted wing Drosophila catches increase slightly in southwest Michigan.

Although overall spotted wing Drosophila (SWD) numbers remain quite low throughout Michigan, we have seen an increase in trap catch in southwest Michigan. Most SWD caught this week were reported in farms producing small fruits: strawberries, raspberries, grapes and blueberries. We saw an increased catch in Berrien County in a tree line next to a cherry and raspberry farm where we trapped six females and two males. Also in Berrien County, we trapped two females in a wood edge in blueberries; one female in high-tunnel strawberries; two males and one female at a strawberry/grape operation; and two females at a vineyard edge.

In Van Buren County, we trapped one SWD in raspberries in high tunnels. We trapped 23 SWD at farms in Allegan County over the past week: three SWD in raspberries; one fly in Niagara grapes; and the remaining flies were trapped in or around blueberry fields. These numbers somewhat reflect the intensity of trapping in the different crops. However, we do have an extensive trapping system in tart and sweet cherries across the state.

Six SWD were trapped in blueberry fields in Ottawa County. Overall, we are catching 0.41 flies per trap and 16.5 percent of all the traps in the state are catching flies, which is an increase from last week’s average catch of 0.91 flies per trap and 5.8 percent positive traps.

As raspberry and blueberry harvest is underway throughout the state, Michigan State University Extension advises growers to be sure to keep this fruit protected through harvest. Growers should make their decisions to spray based on the presence of SWD flies and ripening or ripe fruit that are susceptible, plus the history of pest management inputs to each field. A monitoring program in these crops is recommended throughout the harvest season.

Cherries are another crop at high risk from SWD infestation. Tart cherry harvest in ongoing in southwest and west central Michigan and sweet cherry harvest has started in the north. From preliminary tests conducted at MSU, ripening and coloring sweet and tart cherry fruits are susceptible to SWD infestation. In the last two weeks, we have detected two SWD in tart cherry orchards—one fly in southwest and a second fly in west central Michigan. No SWD have been found in the 60-plus traps in northwest Michigan yet this season.

MSU Extension SWD statewide monitoring
SWD monitoring graph

For more information on SWD and to read past reports, visit MSU‘s Spotted Wing Drosophila website.

The weekly SWD scouting report has been funded through Project GREEEN and Michigan State University Extension.  This output is generated through a scouting and reporting network of MSU Extension field staff and campus specialists. We would like to acknowledge the following team members and thank them for their weekly scouting efforts and input into this report: Rufus Isaacs, Keith Mason, Steve VanTimmeren, Larry Gut, Peter McGhee, Michael Haas, Bob Tritten, Mark Longstroth, Diane Brown, Carlos Garcia, Karen Powers and Nikki Rothwell.

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