Spotted Wing Drosophila

Published: April 1, 2013

Spotted Wing Drosophila (SWD) is a small vinegar fly (about 0.1 inches in length) that for the last two years has been causing economic damage to berries, grapes, and softer-fleshed fruit such as peach in several areas of the US including the Midwest. SWD is also able to attack some vegetables such as tomatoes and peppers. Unlike most other vinegar flies that reproduce on damaged / fermenting fruits, SWD females can cut into healthy fruit using their serrated ovipositor (see Figure 1) to inject eggs under the skin. The adult SWD lives for about two weeks and each female can lay more than 300 eggs. The larvae hatch and feed inside the fruits, causing them to rot. This insect reproduces so quickly that a few adults can give rise to thousands of flies in just a couple of months. It is very important that farmers learn how to monitor for this invasive pest to determine whether SWD is present.

Spotted Wing Drosophila males have one black dot on each wing.

Spotted Wing Drosophila female's wings lack the dot but have a serrated egg-laying structure at the tip of the abdomen.

The most effective and economical trap can be prepared using a clear plastic deli-type cup baited with a mixture of water, dry active yeast, and sugar, as shown in Figure 2. Note the small holes that are made on the sides of the trap which allow flies to enter. A small yellow sticky card can be placed inside the cup so that flies that are attracted by the bait and enter the trap are retained by the card. This allows for easier fly identification.

Diagram of how to make a monitoring trap.
Source: Michigan State University.

For small acreage (or in a high tunnel), researchers suggest setting up one trap for one acre or less whereas for larger farms a minimum of three traps per 5 acres should be placed. Monitoring traps need to be placed inside the vegetation, in the shade. It is also a good idea to put a trap in adjacent woods where activity can be earlier if there are wild berry-bearing plants. Put traps out just before fruit starts to ripen. Check traps and replace yeast + sugar bait on a weekly basis.

On May 30, 2013, starting at 2:00 PM Lincoln University will be offering a field day showcasing IPM among other activities at the organic Busby farm in Jefferson City, MO. At this event, ready-to-use traps and baits will be provided free of cost to farmers that wish to monitor for SWD.

Registration fee for this field day is $5.00. Dinner will be provided at no additional charge. For more information about SWD or about the field day, contact Jaime Pinero (573-681-5522, or at pineroj@lincolnu.edu) or Jacob Wilson (573-681-5591, or at wilsonj@lincolnu.edu).