Michigan spotted wing Drosophila update – July 30, 2019

Julianna Wilson<jkwilson@msu.edu>, Rufus Isaacs<isaacsr@msu.edu> and Larry Gut, Michigan State University Extension, Department of Entomology - July 31, 2019

Spotted wing Drosophila numbers are higher than ever recorded at this time of year in Michigan; take action to protect susceptible fruit.

Male spotted wing Drosophila — Sample of male spotted wing Drosophila (SWD) from a single trap that was collected from a tart cherry orchard in southeast Michigan. Photo by Julianna Wilson, MSU.

Continued warm weather, high humidity and an abundance of susceptible fruit have resulted in the highest recorded numbers of spotted wing Drosophila (SWD) caught in Michigan State University Extension monitoring network traps at this time of the season in Michigan. With more than 98% of traps being monitored catching SWD flies last week, pressure is high and is expected to continue to be tremendous for this pest through the rest of the season in all susceptible crops that are ripe or ripening.

If you have blueberries, cherries or caneberries that are ripe or ripening this week, they are at risk of infestation. A program for managing this pest should already have begun in susceptible crops. See the most recent versions of SWD management guides offered by MSU Extension.

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. Please note that this will be the final SWD update for the 2019 season.

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).

SWD graph — A comparison of average weekly trap captures of SWD in Michigan through the fourth 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, sweet cherries and tart cherries.

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).