April 23, 2018

Spotted wing drosophila

With any fruit crop, it is important to monitor and routinely check for insects and disease.  Once such insect that can be especially devastating to a strawberry crop is the spotted wing drosophila (SWD).

In 2014, we changed our trap cup design.  We used a clear plastic quart-size cup, with lid, as seen below.  We drilled 3/16 inch holes all the way around the cup. A wire handle was inserted into the sides of the cup in order to hang the cup.  The bottom black mark indicates the bait level, while the top black line indicates where the holes were drilled.  We suspended yellow sticky traps inside the lid using twist ties.


Trap bait solution:

  • 12 oz water
  • 4 tbls sugar
  • 1 tbls active dry yeast
  • 1 tbls apple cider vinegar
  • 1-2 tbls whole wheat flour


We filled cups with the solution, up to the black line.  Trap cups are monitored weekly throughout the picking season.  A new trap cup with bait is placed each week. 


Bait solution is added, just up to the black line, so that the yellow sticky trap is above the solution, as seen in the photo on the left. After one week, the bait trap has attracted an assortment of insects (right photo).

For the first time this season, on September 29, 2014, we discovered female SWD in our day neutral strawberry plot.  We had placed several trap cups around the strawberry plot in order to monitor for SWD.  Using a 60X magnification microscope in looking at the yellow sticky traps, we identified three females, each coming from a different trap cup.

As of September 29, 2014, no SWD have been found at the St. Paul day neutral strawberry site.