Climate change: advantage to insect pests

Bad news for Swiss agriculture: several species of insect pests would find an advantage if the climate continues to warm up. This is one of the findings of geographer Léonard Schneider, a PhD student at the joint chair of applied climatology at the University of Neuchâtel and the Swiss Federal Research Institute WSL. His PhD aims to model the impact of global warming in Switzerland on pests. He publicly defended his thesis on May 12.

This is the first time that a study has used climatic data, mainly temperature records, to relate them to the reproduction of insect pests in Switzerland. In this study, Léonard Schneider and his colleagues investigated whether changes in daily temperatures could favour the reproduction of certain pest species.

And this is indeed the case, driven by warmer winters overall, and longer, warmer development seasons. This is particularly striking in the case of pests whose annual reproduction cycle includes several generations, such as the box elder moth or the wine moth, or the codling moth," explains Léonard Schneider. A warmer development season, for example, favors the emergence of one more generation per year. ’

To establish predictive models of this evolution, Léonard Schneider took into consideration the average daily temperature of the development season of these insects. This factor, which runs from April to September, determines whether or not an additional generation will appear.

To do this," explains the researcher, "we collected daily average temperature data over the last 40 years (from 1980 to 2021) from 67 MeteoSwiss measuring stations located between 200 and 2300 meters above sea level. We then used two climate scenarios, predicting different increases in greenhouse gases in the atmosphere in the coming years, to derive the daily average temperature from 2022 to 2099. ’

Both scenarios result in one or more additional generations per year of these insects, but the consequences will be much less severe with lower CO2 emissions.

Other species of pests could also overwinter more easily, continues the researcher who worked under the supervision of climatology professor Martine Rebetez. These include the pine processionary (Thaumetopoea pityocampa) and the green spruce aphid (Elatobium abietinum), as well as certain crop pests such as the green soybean bug (Nezara viridula).

Models show that by the end of the 21st century, future temperature conditions favor some crop pests, allowing them to overwinter more easily on the Swiss Plateau, as well as some forest pests, which will likely reach higher altitudes.

• "The effect of climate change on invasive crop pests across biomes", Current Opinion in Insect Science, 2022
• "Increasingly favourable winter temperature conditions for major crop and forest insect pests species in Switzerland", Agricultural and Forest Meteorology 2021
• "Temperatures during the development season are increasingly favourable for polyvoltine pest species in Switzerland", Agricultural and Forest Meteorology, 2023 (in press)