Michigan spotted wing Drosophila update – July 24, 2019

Julianna Wilson<jkwilson@msu.edu>, Rufus Isaacs<isaacsr@msu.edu>, Larry Gut, Michigan State University Extension, Department of Entomology - July 24, 2019

Spotted wing Drosophila are present and abundant; take action to protect susceptible fruit.

Graph — A comparison of average weekly trap captures of SWD in Michigan through the third week of July by year. Each year SWD has been monitored at more than 70 sites in 17 counties where the majority of fruit production happens in Michigan. The majority of sites being monitored include conventionally-grown strawberries, saskatoons, caneberries, blueberries and sweet and tart cherries.

Warm weather and high humidity have produced a bumper crop of spotted wing Drosophila (SWD) in all fruit production areas being monitored this season. Over the past week, the number of SWD flies caught in Michigan State University Extension monitoring network traps increased 10-fold, which is higher at this time of year than in any previous season since coordinated monitoring began for the pest in Michigan. With more than 90% of traps being monitored catching SWD flies last week, if you have blueberries, cherries or caneberries that are ripe or ripening this week, they are at risk.

Crops at a susceptible stage should have a cover spray of an insecticide that is rated excellent against SWD to prevent infestation. Reapplication after a rain event, tightened spray intervals and properly calibrated sprayers are vital. Remember to rotate insecticide classes once you begin your spray program. Growers can determine how well their program is working by sampling fruit using the salt or sugar test to look for larvae in fruit in the days prior to harvest.

Check out the most recent versions of SWD management guides offered by MSU Extension.

Refresh your ability to identify SWD with MSU Extension’s Spotted Wing Drosophila Identification Guide.

For more information on effective insecticides registered for use to control SWD, refer to MSU Extension’s Michigan Fruit Management Guide for 2019 (E-154).

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).