Switzerland: Fewer carrot flies due to global warming
According to the Intergovernmental Panel on Climate Change (IPCC), temperature rise in the course of the 21st century is considered inevitable. In agriculture, this could promote mass propagation of insects. However, a major agricultural pest reacts the other way around: the carrot fly (Psila rosae). It is one of the vegetable flies and is an important pest in carrot cultivation in Northern and Central Europe. It is monitored in Switzerland by default with traps, which makes their activity visible. From a critical catch number onwards (the so-called damage threshold) damage to crops is to be expected, which is why an insecticide treatment is recommended according to the principle of Integrated Pest Management.
In the summer heat, the fly larvae die
As the data from the traps shows, the carrot fly in German-speaking Switzerland developed three complete generations in years with very wet summers (2007, 2014). In contrast, in many locations the third carrot fly generation after summers with pronounced heat spells was extremely small - as happened in 2006, 2013, 2015 and 2017. In those years, ground temperatures at a depth of 10 cm were over 23° C for several weeks in June or July, which increased the mortality of larvae and pupae of the carrot fly or led to a temporary development stop of the pupae. Even with the second generation of carrot flies, a flight delay was increasingly noticeable.
The carrot fly is therefore sensitive to dryness and heat. Therefore, climate change in German-speaking Switzerland could favor the occurrence of development breaks and possibly reduce the number of generations per year.
Global warming will influence population dynamics
For food security in times of climate change, trap monitoring, field controls and forecasting systems are becoming increasingly important. This is the only way to react in time to the changed appearance of pests or to new immigrant insects.
For this reason, Agroscope maintains a monitoring network against harmful organisms, working closely with the Cantonal Vegetable Development Centers, the Research Institute of Organic Farming and other partners. The information on the infestation situation is supplemented with information on the protection of crops and published weekly for the vegetable producers in special bulletins: in the Horticulture Info, the Info Cultures Maraîchères and the Orto Fito Info. In addition to the early detection of harmful organisms in times of climate change, this will create a basis for risk reduction and the sustainable use of plant protection products, which are required by the Federal Council in the Plant Protection Products Action Plan.
Source: Agroscope