Michigan spotted wing Drosophila report for July 8, 2016

Julianna Wilson<jkwilson@msu.edu>, Rufus Isaacs and Larry Gut, Michigan State University Extension, Department of Entomology - July 08, 2016

Numbers are up throughout the network this week; susceptible crops need to be protected.

This is the Michigan State University Extension spotted wing Drosophila (SWD) Statewide Monitoring Network report. Out of the 147 traps collected during the week prior to July 7, 139 females and 131 males for a total of 270 SWD flies were captured from 56 traps, or 38 percent of the traps being monitored. That is a 31 percent increase over last week and an 81 percent increase over two weeks ago.

As of this week, SWD adults have been captured in traps baited with commercial lures in strawberry (Berrien, Livingston and Ottawa counties), blueberry (Allegan, Berrien, Ingham, Ottawa and Van Buren counties), raspberry (Allegan, Berrien, Van Buren counties), grape (Benzie, Berrien, and Grand Traverse counties) and cherry (Allegan, Antrim, Benzie, Berrien, Grand Traverse, Leelanau, Kent, Macomb, Monroe, Oceana and Van Buren counties) 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.
Region	Counties covered in the SWD monitoring network	No. sites*	Cumulative SWD Total
SE	Genesee, Ingham, Lenawee, Livingston, Macomb, Monroe, Oakland	19	22
SW	Allegan, Berrien, Kalamazoo, Ottawa, Van Buren	79	410
Ridge	Ionia, Kent, Muskegon	14	104
WC	Mecosta, Oceana	9	16
NW	Antrim, Benzie, Grand Traverse, Leelanau, Manistee	61	79
	Grand Total:	182	631
* Note: not all sites are monitored each week.

Average trap catch over the entire network is now over 2 SWD flies per trap in the southern part of the Lower Peninsula and 1 SWD fly per trap in the northwest counties. Some sites reported more than 20 SWD flies per trap. Ripening fruit throughout the state are likely to be at risk for infestation if not protected, especially in southwest and fruit ridge counties.

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 = 50 traps this week). Southern LP encompasses all network traps in counties south of Clare in the Lower Peninsula (n = 97 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, Mecosta, Monroe, 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.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).