Michigan spotted wing Drosophila report for July 29, 2016

Trap catches remain high, especially near untreated plantings – high risk of infestation continues to be expected – susceptible crops must be protected.

This is the Michigan State University Extension spotted wing Drosophila (SWD) Statewide Monitoring Network report. Trapping has concluded in plantings where harvest is already complete (June-bearing strawberries, southwest cherry orchards, etc.), but continues in most blueberry, raspberry and grape sites in the network and also in northwest cherry orchards. Out of the 111 traps collected during the week prior to July 28, 2,210 female and 1,886 male SWD were captured for a total of 4,096 SWD flies. We found SWD in 93 traps, or 84 percent of the traps being monitored.

Average SWD catch in the traps being monitored this week is now over 46 SWD flies per trap in the southern part of the Lower Peninsula, which is a doubling from the numbers trapped last week. In contrast, the numbers are much lower at 3 SWD flies per trap in the northwest counties. Ripening fruit throughout the state are at high risk for infestation if not protected. Check with local Extension staff or crop consultants, and refer to the "2016 Michigan Fruit Management Guide” for recommendations for your crop(s). 

Table 1. The regions that are being monitored for SWD in 2016, how each region is defined (by the counties listed), the number of sites in each region that were monitored this week, the cumulative total of SWD flies caught in traps by region and the average number of SWD flies caught per trap.


Counties covered in the SWD monitoring network

No. sites this week

Cumulative SWD Total

Avg SWD flies per trap*


Genesee, Ingham, Lenawee, Livingston, Macomb, Monroe, Oakland





Allegan, Berrien, Kalamazoo, Ottawa, Van Buren





Ionia, Kent, Muskegon





Mecosta, Oceana





Antrim, Benzie, Grand Traverse, Leelanau, Manistee





Grand Total:




* Average is for the week ending July 28, 2016

Northern LP bar graph

Southern LP bar graph

All sites bar graph

Bars represent the average number of SWD flies caught in monitoring network traps each week. Dots represent the percent traps that captured SWD that week. The shaded bar across each graph represents the proposed threshold for triggering management of the pest in susceptible crops. Northern Lower Peninsula (LP) encompasses all network traps in counties north of and including Clare in the Lower Peninsula (n = 24 traps this week). Southern LP encompasses all network traps in counties south of Clare in the Lower Peninsula (n = 87 traps this week).

Traps in the network are baited with commercially available lures and placed in susceptible crop fields or orchards, or in a location adjacent to susceptible crops, in areas where SWD infestation has been recorded in the past. Commercial plantings included strawberry, blueberry, raspberry, grape, tart and sweet cherry, peach and plum. Counties included in the 2016 trapping network are Allegan, Antrim, Benzie, Berrien, Genesee, Grand Traverse, Ingham, Ionia, Kalamazoo, Kent, Leelanau, Lenawee, Livingston, Macomb, Manistee, Mecosta, Monroe, Muskegon, Oakland, Oceana, Ottawa and Van Buren.

For the most current recommendations for monitoring this pest, please refer to “Monitoring traps for catching spotted wing Drosophila.” You can find out more about how to identify and manage this pest in fruit crops by visiting MSU’s Spotted Wing Drosophila website.

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