Monitoring and controlling Drosophila suzukii in Switzerland

Abstract: Drosophila suzukii is a highly polyphagous vinegar fly native to Asia, which invaded Switzerland in 2011. The monitoring survey begun in 2012 and the network consisted of about 200 traps distributed according to the importance of fruit growing areas. Drosophila suzukii was found in all regions of the country, from low altitudes to the timberline. The range of the pest’s host plants is very broad and does not only include crops, but also wild fruits. Most individuals were captured close to or within cultivated raspberry, blackberry and grapevine as well as within wild shrubs such as elderberry. Monitoring traps can reliably detect the occurrence of the pest in a region. In 2013, an intensive survey was set up in order to study the attractiveness of different host towards D. suzukii Results showed that cherry and raspberry were highly attractive throughout the season. Even when there were no more fruits on the plant, they continued to capture lager numbers of D. suzukii. Cherries and raspberry therefore seem to be good host plants for installing survey traps that monitor population dynamics over the whole seasonDue to its fast reproduction rate and the infestation of fruits shortly before harvest D. suzukii is difficult to control. When D. suzukii was found in a monitoring trap in a region, sanitary measures and mass trapping were immediately set-up in the berry crops of the particular region. Sanitary measures included a shorter picking interval and the immediate destruction of all unmarketable fruits. Mass-traps were either deployed in a dense net around the crop or between hedges and a culture in order to capture D. suzukii before they attack ripe fruits. These control measures were satisfying, although economic damages differed between 2012 and 2013. Whereas fewer attacks were reported in 2012, many economic damages were reported in 2013 especially in late harvested crops such as raspberries and blackberries.