Michigan spotted wing Drosophila report for August 12, 2014

Spotted wing Drosophila numbers continue to rise across the monitoring network. Protect susceptible crops where they are detected.

This is the eighth 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 Aug. 4 and shows that SWD activity is continuing to increase, particularly in southwest and west central counties. There was a total of 1,268 male and 513 female SWD trapped from the following counties in our trapping network: Berrien, Van Buren, Allegan, Ottawa, Kalamazoo, Kent, Montcalm, Oceana, Muskegon, Leelanau, Benzie, Grand Traverse, Ingham, and new this week, Ionia. No SWD were captured in Antrim County traps this week. Traps in Genesee, Lapeer, Livingston, Macomb and Oakland counties will be checked later this week with an update to this report at that time.

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 31 sites in the northwest (NW) counties of Antrim, Benzie, Grand Traverse, and Leelanau; two sites in the southeast (SE) county of Ingham; 46 sites in the southwest (SW) counties of Allegan, Berrien, Kalamazoo, Ottawa, and Van Buren; and 19 sites in the west central (WC) counties of Ionia, Kent, Montcalm, Muskegon, and Oceana.

SWD graph

Of the traps that were checked so far this week, 68 percent of traps contained SWD, which is up from 53 percent last week. The average number of SWD per trap is also up from 10 last week to 18 this week across the network, with more than 33 SWD per trap on average in southwest counties. If SWD has not been found 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 and west central regions. Susceptible crops include most thin-skinned fruit, such as raspberries, blueberries and cherries.

Spotted wing Drosophila can only infest fruit when they are ripening or ripe, so the focus of SWD monitoring and management efforts should be in susceptible fruit that should be treated only if SWD are detected to minimize the risk of developing pesticide-resistant populations of SWD. 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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