Milder winters favour insect pests

In Switzerland, the severity of winters is a key factor influencing the distribution and abundance of various species, particularly insects. Ongoing climate change is likely to favor species that are vulnerable to extreme cold events. In this article, the authors studied the evolution of winter temperatures over the last 40 years, with a focus on daily minima. They also made projections for the next decades using climate scenarios. The objective was to evaluate the potential impact of this evolution for several cold-sensitive insect pests: the green spruce aphid, the pine processionary moth and the green soybean bug. The results show a decrease in severe cold events in recent decades, even though winter temperatures are increasing less rapidly than the annual average. By the end of the century, it can be expected that the critical lethal temperature thresholds will be reached less than one winter out of two for the green spruce aphid and the pine processionary moth, including in mid-mountain areas up to 1700 m altitude. The milder conditions are also expected to favour the establishment of invasive pests such as the green soybean bug in the Swiss plateau.