Michigan spotted wing Drosophila report for August 6, 2014

Spotted wing Drosophila numbers are up from last week and are now being detected statewide. Protect susceptible crops where SWD is detected.

This is the seventh weekly report of the Michigan State University Extension spotted wing Drosophila (SWD) statewide monitoring program for 2014. Our network of traps across more than 100 sites was checked during the week of July 29 and shows increased activity of this pest, particularly in southwest Michigan counties. There was a total of 663 male and 454 female SWD trapped from the following counties in our trapping network: Berrien, Van Buren, Allegan, Ottawa, Kalamazoo, Kent, Montcalm, Oceana, Leelanau, Benzie, Ingham, Macomb, Oakland, and new this week, Muskegon, Mecosta, Antrim, and Grand Traverse counties. No SWD were captured in Ionia, Genesee, Lapeer or Livingston county this week. 

Comparison of average trap catches by week between 2013 and 2014.

SWD graph

Comparison of average SWD adults captured per trap by region. This week trapping is reported from 35 sites in the northwest (NW) counties of Antrim, Benzie, Grand Traverse, and Leelanau; 12 sites in the southeast (SE) counties of Ingham, Genesee, Lapeer, Livingston, Macomb and Oakland; 46 sites in the southwest (SW) counties of Allegan, Berrien, Kalamazoo, Ottawa, and Van Buren; and 18 sites in the west central (WC) counties of Ionia, Kent, Montcalm, Muskegon, and Oceana.

SWD graph

Of the traps that were checked, 53 percent of traps captured SWD this week, which is up from 40 percent last week. The average number of SWD per trap is also up from four last week to 10 this week across the network, with more than 21 SWD per trap on average in southwest Michigan. If SWD has not been trapped in your monitoring traps, be on alert for this pest as susceptible fruit crops start or continue to ripen as it seems that the mid-late summer increase in population is underway, at least in the southwest region.

Sampling of fruit over the past week in conventionally managed sites has yielded few larvae in either summer raspberries or blueberries. However, unsprayed sites are showing low to moderate fruit infestation depending on the site and fruit variety. This highlights the need for protection of ripe berries over the coming weeks as the SWD population continues to grow.

SWD can only infest berries when they are ripening or ripe, so the focus of SWD monitoring and management efforts should be in these susceptible fruit. In addition to the use of monitoring traps to detect the adult flies, a simple salt solution of 1 cup of salt per gallon of water can be used to assess fruit for larval infestation. Leave the fruit in the solution for a minimum of 15 minutes then check for small white larvae.

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

The weekly SWD statewide monitoring report has been funded through Project GREEEN and Michigan State University Extension. This output is generated through a 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, Brad Baughman, Carlos Garcia, Karen Powers and Nikki Rothwell.

Dr. Isaacs' work is funded in part by MSU’s AgBioResearch.

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