Michigan spotted wing Drosophila report for July 22, 2016

Big jump in trap catches this week – high risk of infestation expected across the state – susceptible crops must be protected.

This is the Michigan State University Extension spotted wing Drosophila (SWD) Statewide Monitoring Network report. Out of the 148 traps collected during the week prior to July 21, 1,426 females and 1,270 males for a total of 2,696 SWD flies were captured from 110 traps, or 74 percent of the traps being monitored. That is a 79 percent increase over last week.

 As of this week, SWD adults have been captured in traps baited with commercial lures in strawberry (Berrien, Livingston, Macomb, Ottawa Counties), blueberry (Allegan, Berrien, Ottawa and Van Buren Counties), raspberry (Allegan, Berrien, Ingham, Kalamazoo, Macomb, Ottawa, Van Buren Counties), grape (Benzie, Berrien, Grand Traverse, Leelanau, Van Buren Counties), cherry (Allegan, Antrim, Benzie, Berrien, Grand Traverse, Leelanau, Lenawee, Kent, Macomb, Manistee, Monroe, Oceana, Van Buren Counties), and peach (Berrien, Kent County) blocks. 

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, and the cumulative total of SWD flies caught in traps by region.


Counties covered in the SWD monitoring network

No. sites*

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:




* Note: not all sites are monitored each week.

** Average is for the week ending July 21, 2016

Average trap catch over the entire network is now over 22 SWD flies per trap in the southern part of the Lower Peninsula and 6 SWD fly per trap in the northwest counties. Traps catching the most flies came from the southwest region, which had an average of more than 27 SWD flies per trap. Some southwest Michigan sites reported more than 100 SWD flies per trap. Ripening fruit throughout the state are at high risk for infestation if not protected.




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 L.P. encompasses all network traps in counties north of and including Clare in the Lower Peninsula (n = 37 traps this week). Southern L. P. encompasses all network traps in counties south of Clare in the Lower Peninsula (n = 111 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 include 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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