Spotted Wing Drosophila

Drosophila suzukii

Insectalso: SWD, Vinegar fly

An invasive vinegar fly that, unlike its harmless kitchen-fruit-fly cousins, attacks sound, ripening berries and cherries rather than only rotten fruit. The females saw into firm fruit to lay eggs, and the maggots turn the berries soft and mushy from the inside as they ripen.

🔎 How to spot it

The adults are tiny tan flies, about a sixteenth of an inch, with red eyes; the males have a single dark spot near the tip of each wing, while females lack the spot but carry a large, saw-like egg-laying organ. The maggots are small white grubs inside the fruit. Tell-tale signs are soft, sunken, leaking spots on berries, pinprick holes in blueberries, and juice weeping where a raspberry was picked.

🥀 Damage it causes

Females cut into ripening, undamaged soft fruit and lay eggs just under the skin; the hatching maggots feed inside, so berries collapse, soften, and rot quickly, often only after picking. Raspberry, blackberry, blueberry, strawberry, and cherry are the main targets, and a planting can go from fine to infested within days of ripening.

🛡️ Prevent it

Harvest ripe fruit frequently and completely, and remove and destroy every overripe, dropped, or culled berry so the flies have nowhere to breed; do not compost infested fruit loosely. Where pressure is high, exclude the flies with very fine insect netting (mesh under one millimeter) installed before fruit colors. Prune plantings open so fruit dries and is easy to pick clean.

🧯 If it is already here

There is no rescue for fruit already infested, so sanitation is everything: strip and bag spoiled fruit, and chill picked berries promptly, since refrigeration stops the maggots. Hang cup traps baited with apple cider vinegar or yeast-sugar water to detect when adults arrive and time action. Spinosad is the main organic spray when monitoring shows the flies are active.

💡 Good to know

Monitor traps tell you when SWD has arrived so you can tighten harvest and sanitation before damage shows. Because the flies breed explosively over a season, gardeners who keep fruit picked clean and drops removed fare far better than those who rely on sprays alone. A week of plastic-bagging infested fruit in full sun also kills the eggs and larvae.

🌱 Plants it attacks

53 plants in the library can be attacked by this pest

For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.