Spotted Wing Drosophila

spotted wing spotted wing pattern


All fruits, especially soft fruits


Overwinter as adults and pupae; adults lay eggs inside fruit and maggots feed on pulp.  SWD adults have been trapped in Utah orchards, but no fruit injury has been detected.


Sunken fruit; holes in fruit.


SWD has been found in northern Utah in low numbers, and in north-central Idaho in high numbers.  It is established in northwestern Montana in Lake and Flathead Counties.  Monitoring should be done using traps containing a cider vinegar or sugar-yeast bait.  See the USU Spotted Wing Drosophila factsheet for more detailed information on monitoring techniques.

Treatment Threshold

None determined yet.

Degree Day Model

  • Lower threshold:  50°F
  • Upper threshold:  88°F
  • Start date:  Jan 1
  • Peak adult emergence:  755 DD after Jan 1

Management Considerations

Monitoring will help to determine if this pest has been introduced to your area.