Monitoring Drosophila suzukii in Switzerland in 2012

BACKGROUND: Drosophila suzukii is a highly polyphagous vinegar fly native to Asia, which invaded Switzerland in 2011. The pest was found in all regions of the country, from low altitudes to the timberline. Due to its fast reproduction rate and the infestation of fruits shortly before harvest D. suzukii is difficult to control. OBJECTIVE: Our main objective was to establish an efficient monitoring campaign all over Switzerland. RESULTS: In 2012, a total of 60,000 D. suzukii were captured in 200 monitoring traps, whereupon it represented between 25 and 75% of all vinegar flies trapped. The range of host plants is very broad, not only affecting crops, but also wild fruits. In 2012 most individuals were captured close to or within cultivated raspberry, blackberry and grapevine as well as in wild shrubs such as elderberry. It is likely that as a result of a consequent application of the recommended sanitation measures, only very few cases of economic damage were reported by the producers in 2012. CONCLUSIONS: Monitoring traps can reliably detect the occurrence of the pest in a region. The trap must be very selective to small insects (diameter of 3 mm) to avoid other beneficial insects such as Lepidoptera and Hymenoptera being caught. In case of local presence, setting up a dense net of mass-traps around the crop or between a hedge and the crop should guarantee capture of most vinegar flies before they attack ripe fruits. In close collaboration with national and international partners, Agroscope will try to identify pragmatic and sustainable crop protection measures against D. suzukii.