Spotted wing drosophila (SWD), Drosophila suzukii has become a potential concern for strawberries following its damage to cherries, blackberries, raspberries, and blueberries in coastal California. Other species of Drosophila are morphologically not equipped to attack ripening strawberries.  Their ovipositors or egg laying parts are not strong enough to penetrate unripe or ripening berries.  They may damage overripe strawberries left on the crop, but since such berries are not marketed, they have not been an issue for growers.  However, SWD has a heavily sclerotized, serrated ovipositor that enables it to lay eggs in fruits that are not fully ripe.

In response to the concern that SWD could be a potential pest to strawberries, I monitored some fields in Santa Maria last year.  Five fields – four conventional and one organic – in various parts of Santa Maria were monitored for five months from March to July, 2011.  Two kinds of traps, one with apple cider vinegar and the other with yeast-sugar extract were used in each location and were observed every week.  During this monitoring there were no signs of SWD in any of these traps.  However, I recently received some samples in which I found what seemed to be the females of SWD among other Drosophila sp.  There were no males with their obvious characteristic of spotted wings, but the following and other characters of the females suggest these were SWD:

 

• Hard and dark (sclerotized) ovipositor with prominent serrations or saw-teeth that enable the fly to lay eggs in intact ripening fruit.

• Antennae with branched bristle-like part called arista.

 

 

According to Dr. Brian Cabrera, Santa Barbara County Ag Commissioner Entomologist, there haven’t been any SWD infestations that were brought to his attention.  So, it appears to be the first report of SWD in Santa Maria strawberries.  Sanitation, trapping, and chemical control are among the available options to manage SWD.  Close monitoring is necessary in vulnerable areas.  More details about identifying and managing SWD can be found in the listed references.  Here is a brief note about this pest.

SWD belongs to the group of flies that are generally known as vinegar flies or lesser fruit flies.  It was initially known as cherry fruit fly in 1930s and is now referred to as spotted wing drosophila.