Spotted wing drosophila (Drosophila suzukii, or SWD) attacks several fruits in Oregon. It is crucial that growers identify an infestation early. Trapping can determine the presence of adult SWD in fields. The fruit-dunk method can be used to identify larval fruit infestation, but larvae must be large enough to be easily identified in the liquid mixture. In addition to these methods, early field identification of damage symptoms may be a tool to help growers identify SWD in fruit.
This publication shows damage caused by SWD on blueberries (Duke), raspberries (Malahat), strawberries (Seascape), cherries (Bing, Montmorency and Rainier) and grapes (pinot noir, chardonnay). Pictures show each fruit type a day or two after egg-laying, three to four days later, and approximately one week after egg-laying. Some pictures show uninfested berries and symptoms observed among fresh commercial fruit in Oregon fields
Summary of symptoms
Observed symptoms due to SWD infestation
- Early mold, wrinkling and softening seen at two to three days
- Soft spots and collapse of berry structure
- Small holes created by larvae for breathing. Sometimes breathing tubes visible.
- Expulsion of berry sap from oviposition holes
- Scarring of tissue
- Dark spots in white grapes, light spots in dark grapes. (Do not confuse with lenticels.)
- Splitting of grape berries
- Larvae emerging from berries
- Pupae in or outside berries
Observed damage likely due to aging
- Most mold in approximately four to five days
- General wrinkling and softening without specific soft spots
- Darkening of skin
Recognize fruit damage from spotted-wing drosophila
Strawberries
Infested fruit
Infested fruit
Infested fruit
Uninfested fruit
Raspberries
Infested fruit
Infested fruit
Infested fruit
Uninfested fruit
Cherries
Infested fruit
Blueberries
Infested fruit
Infested fruit
Infested fruit
Infested fruit
Infested fruit
Uninfested fruit
Grapes
Infested fruit
Field-infested fruit
