Monitoring the adult flight of spotted-wing drosophila will be important before grape development in the spring. The presence of the pest is the first step in choosing future management strategies. Monitoring can persist throughout the growing season. All growers are encouraged to do their own on-site monitoring for this pest.
- Clear plastic disposable cup.
- Fitted plastic cap.
- Yellow sticky trap.
- Metal hanger or wire.
- Apple cider vinegar or sweet white wine.
Steps to constructing trap
- Drill four to five 3/16–3/8-inch holes inside of the container for entry of the flies. Leave 3 inches pour space for vinegar.
- Cut a cross-section in the top of the lid to allow hanging of the sticky trap.
- Affix a twist-tie or wire to the top of a yellow sticky card and affix it to the top of the lid for easy removal.
- Pour 1 1⁄2 inches of apple cider vinegar in the bottom of the cup, making sure to keep the sticky trap above the liquid.
- Close the top and place the traps in areas you wish to monitor in the vineyard.
- One trap will service 1 acre. Place in or near the fruiting wire of the trellis or on the ground later in the season where thinned fruit may persist.
Begin monitoring when the daily temperature climbs above 50oF for several days. Collect the sticky traps each week for observation. Identify and count the flies on the yellow trap and in solution.
SWD are larger than the typical drosophila melanogaster fruit flies (also known as vinegar flies) and males are easily distinguished by the black dot on their wings. A 30X hand lens can help you identify the black dot on the wings (males only) and the red eyes. They may also be seen with the naked eye. Females do not have these black dots on the wings, but have a distinctive saw-like ovipositor on their posterior.
Replace the sticky card and vinegar once a week.
Monitoring for SWD in vineyards will help determine its presence and management if required.
Once you identify the presence of SWD, you can refer to management guidelines online. This is a new pest to the West Coast, and management recommendations may change in the future as researchers study SWD.
We are still uncertain how SWD impact wine grapes and production. The best method is to monitor and manage the pest before it becomes a significant problem for grape and other fruit industries in the state.