Possible impacts of climate change on carrot fly’s population dynamics in Switzerland

Abstract: Temperature increase is very likely in the course of the 21st century. Temperature-related impacts such as outbreaks of pests might pose a challenge in agriculture. The carrot fly, Psila rosae (Diptera: Psilidae), is the most serious pest in Swiss carrot production. Since the early 1990s the carrot fly has been able to complete three generations in years with a fully humid and warm summer (e. g. 2007, 2014) under conditions in north and central Switzerland, whereas in 2006, 2013, 2015 and 2017 only weak flight activity of the third carrot fly generation was observed. During the summers of these years heat waves caused an increase of soil temperature (-10 cm) approximately to or above 23 °C. These findings are in line with earlier reports that larval and pupal survival or pupal development of the carrot fly are affected by temperatures within that range. The risk of the carrot fly developing a third generation is expected to be more unlikely in north and central Switzerland during the following decades. Global warming includes potential shifts in population dynamics of pests. Peak activity might vary more pronouncedly between years. Therefore, monitoring and forecasting systems are of increasing importance for sustainable farming systems.