Michigan spotted wing Drosophila report for August 31, 2015

Susceptible crops must be protected or risk infestation by spotted wing Drosophila across the state.

In the 12th week of monitoring spotted wing Drosophila (SWD) this season, all of our traps caught SWD. There were 2,456 females and 2,171 males for a total of 4,627 flies captured in 105 out of the 105 traps, which is 44 percent more than last week.

It is essential to maintain fruit protection on ripe or ripening susceptible fruit throughout the state: maintain coverage with effective insecticides, re-apply after rain, alternate among insecticides with different modes of action to reduce the risk of creating insecticide-resistant SWD populations, and do not stretch your spray intervals too far. Growers can consult the Michigan State University’s Spotted Wing Drosophila website where there are crop recommendations posted for berry crops, or contact your local Michigan State University Extension fruit educator for more information on management strategies.

If you are not using traps to monitor for adults of this pest, finding fruit that is softer than expected is a telltale sign of infestation by SWD in cherries, blueberries, raspberries and other thin-skinned fruit. A salt test is strongly recommended prior to harvest to help determine whether protective measures are working or if your management program needs to be adjusted. For instructions on how to conduct a salt test, please refer to the July 28 SWD report.

The purpose of the Michigan State University Extension spotted wing Drosophila (SWD) monitoring network is to provide growers with regional trends in SWD population growth. Traps in the network are baited with Trece lures and placed near susceptible crops and wild hosts in each of the major fruit growing regions across the state. Commercial plantings include strawberries, blueberries, raspberries, grapes, tart and sweet cherries, peaches and plums. Wild hosts in the trapping network include autumn olives, black cherries, pin cherries, choke cherries, blackberries, honeysuckle, mulberries and wild grapes. For instructions on how to construct your own traps and use them for monitoring for SWD, please visit the MSU Spotted Wing Drosophila website.

SWD graph

Average number of spotted wing Drosophila flies caught in traps in four Michigan fruit production regions. This week: NW = 61 traps in Antrim, Benzie, Grand Traverse, Leelanau and Manistee Counties; SE = 5 traps across Ingham, Lenawee and Monroe; SW = 26 traps across Allegan, Berrien, Ottawa and Van Buren; and WC = 13 traps in Ionia, Kent and Oceana.

SWD graph

Average number of spotted wing Drosophila (SWD) captured per trap (red bars) and the percentage of traps that captured any SWD (blue line) across the entire trapping network by week starting in June 30, 2015.

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