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Insects - Spotted Wing Drosophila Traps

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Prepared by Frank Drummond, Professor of Insect Ecology/Entomology, The University of Maine, Orono, ME 04469.  April 2013.

Monitoring for Spotted Wing Drosophilia – This video demonstrates how to use red cup traps in fields for monitor of the spotted winged drosophila, how to identify males and females, and how to monitor berries for larvae using the “salt extraction method.”

Spotted Wing Drosophila Traps (PDF)


  • Live yeast (1 Tbsp)
  • Sugar (4 Tbsp)
  • 12 ounces water
  • 4 to 6 foot stake and large clamp holder ( for hanging cup)
  • One-Pint RED transparent deli containers with lids
  • Electric drill or punch with 1/8 -inch punch size drill bit. Note hole size is important -if it is larger you will trap all kinds of flies making ID much harder.

For the bait: Stir together live yeast, sugar and water in a container large enough to handle some expansion. Let the mixture ferment 24 hours. One can use pure apple cider vinegar as bait. It is easier to deploy and lasts longer in the field, but it is less effective in attracting SWD.

For the traps: Drill seven or punch 1/8-inch holes near the top of the deli containers, evenly spaced, leaving 1/8 of the rim diameter without a hole so you can pour used bait out that side without it leaking out of a hole. This works better if the drill bit or punch is hot.

Place stake at the edge of the field with the cup attached at about eye height 4-6 feet. In large fields, traps should also be placed in the field interior at 3-4 ft high.

Add fermented bait to containers (about 1 ½ inches of fluid in the bottom of the cup is enough, snap on the lids, and hang the traps. 

Traps should be placed in multiples about 25-50 ft apart, so at least 2 traps along the field edge and 2 traps in the field interior in larger fields where the edge is a considerable distance from the field. Traps should be visited at least once per week, but preferably twice a week. During each visit, fly samples should be collected from the traps and then the traps should be emptied and replaced with fresh bait.


The adults are small (2-3 mm) flies with red eyes and a pale brown thorax and abdomen with black stripes on the abdomen, see Figure 1.  The most distinguishable trait of the adult is that the males have a black spot towards the tip of each wing. 

Fig. 1.  Spotted Wing Drosophila.

Spotted wing drosophila

Fig. 2.  Trap and holder, not holes on left, for monitoring spotted-wing drosophila.

 Red Cup Close up for SWD traps     SWDTraponStake

Information in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of products or services mentioned. No endorsement of products or companies is intended, nor is criticism of unnamed products or companies implied.

© 2013
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