Spotted wing Drosophila detections are increasing in fruit crops

Monitor ripening fruit crops to know where and when to protect against spotted wing Drosophila, a new pest to Michigan.

Captures of spotted wing Drosophila (SWD) in monitoring traps have increased recently, with higher numbers of flies trapped as well as an increasing number of monitoring sites showing activity. In our monitoring network, total captures have climbed from only one female SWD trapped in the week of May 29, to six males and 16 females in the week of June 8. In the past week, we have trapped seven males and 22 females.

At this time, SWD activity has been detected in Van Buren, Allegan and Ottawa counties. The majority (86 percent) of the female SWD trapped this past week have been caught in monitoring traps baited with a yeast-sugar solution, rather than in traps baited with apple cider vinegar. This solution can be made by mixing 1 tbsp of active dry yeast, 4 tbsp of sugar and 12 oz of water. This will make enough liquid for multiple traps. For more information on how to build traps to monitor SWD, take a look at the information on the MSU IPM Spotted Wing Drosophila website.

The catches of SWD a full month earlier than in 2011 highlight the need for monitoring so you know where and when to protect susceptible fruit. It is also important to know that berries become susceptible to infestation by SWD only when the fruit start to soften during ripening. This means that crop protection activities should be focused on the earliest varieties, whereas the later varieties that still have green berries are not yet at risk.

There are a number of insecticide options with activity against SWD, which is best controlled by organophosphate, pyrethroid or spinosyn class insecticides. Full details of the effective options available for blueberry growers are available in the SWD Management Recommendations for Michigan Blueberry Growers.

Dr. Isaacs’ work is funded in part by MSU’s AgBioResearch.