Small Fruit Alert: Spotted Wing Drosophila (SWD) - 2026

This includes late-season strawberries, red and black raspberries, blueberries, blackberries, cherries and late-season peaches.

It is easier to identify the males since their characteristic wing spots differentiate SWD from other fruit flies.  If males are present, it means females are also present to lay eggs in the fruit. Signs that SWD is present include soft areas on strawberries, juice on the receptacles of raspberries once the berry is pulled off, light-colored or soft individual drupelets on blackberries, and pinprick-sized holes in blueberries. Sunscalding on strawberries and blueberries, which often occurs when hot sunny spells follow cool cloudy ones, can be mistaken for SWD presence.

If you wish to monitor for SWD, you can use SWD lures and traps, apple cider vinegar traps, or red sticky cards.

Monitoring over the past few years has shown that an SWD wasp parasitoid is present in very many locations - essentially everywhere we checked.  This parasitoid emerges at about the same time as SWD emerges in the spring, and is found in the same overwintering locations as SWD.   We no longer recommend removing wild plant hosts of SWD from wooded locations, in part because monitoring also raised the question of whether removing wild hosts may tend to concentrate SWD in managed plantings.        

Other cultural controls should be used to the extent possible. Fruit should be harvested frequently and thoroughly. Any cull fruit should be removed from the field and bagged. Landscape fabric in raspberry plantings makes it easier to keep cull fruit cleaned up off the ground. Fruit should be refrigerated as close to 32 degrees as possible immediately after picking. Plantings should be kept weeded and pruned, which will make the environment less favorable to SWD and allow sprays to better infiltrate the canopy.

Many different insecticide sprays have very good efficacy on SWD, but this is dependent on good coverage and roughly a weekly spray schedule. That means that rotating pesticide chemistries is important to avoid resistance development. Effective pesticides are in certain chemical classes, specifically the pyrethroids (Mustang Maxx, Brigade, Danitol), spinosyns (Delegate, Radiant), diamides (Exirel, Verdepryn), certain organophosphates (malathion and for blueberries, Imidan) and carbamates (Lannate, for blueberries only).  Malathion works best at higher rates; therefore, for blueberries, PA and some other states have a Special Local Needs (Section 24C) label that allows a higher rate with a longer (2-day) PHI compared to the typical (Section 3) label.  Lannate, Brigade, Danitol, and Mustang Maxx are restricted-use products.  

Those using organic practices can use Pyganic or Entrust, but be aware that some SWD resistance to these products has already been found elsewhere. 

Spotted wing drosophila may not appear on all labels for all products listed above. In PA, a pesticide can be used for a pest not on the label as long as the timing, rate, site of application, re-entry, and pre-harvest intervals, and any other specifications stated on the label are observed. If you are outside PA, consult the label and your state’s registration requirements for allowable products in your state.

For information in more detail, please see the following:

• Spotted Wing Drosophila Part 1: Overview and Identification
• Spotted Wing Drosophila, Part 2: Natural History
• Spotted Wing Drosophila, Part 3: Monitoring
• Spotted Wing Drosophila Part 4: Management