Assessing climate change impacts on fruit plant and pest phenology and their synchrony: the case of apple and codling moth

Temperature is a main climatic driver of plant phenology and the dominant abiotic factor directly affecting insect pests. Global warming is therefore expected to accelerate the development of plants and insects alike. In the case of multivoltine pest species, it was shown that higher temperatures lead to the appearance of additional generations toward the end of the warm season (Stöckli et al., 2012), which also has implications for pest management. The same effect was shown for the timing of flowering termination of apple trees (Stöckli and Samietz, 2015), the time when a pest can attack a fruit. In practice, however, much would depend on whether plant and pest phenology remain synchronized or not. Focusing on Switzerland, in this contribution we present an analysis of potential impacts of climate change on plant and pest phenology. and their interlinkages at the example of the apple tree (Malus pumila L.) and the codling moth (Cydia pomonella L.), a fruit crop of economic relevance worldwide. Key developmental stages of the apple and the codling moth were simulated by means of two heat summation models. The models were calibrated with lab and field data from Switzerland and subsequently run with observed weather data and various climate change scenarios. The time period between flowering termination and the harvest of the apples was compared to the appearance of the second and third generation of codling moth larvae to study the interlinkage between host and pest. To illustrate the potential for practical applications of the phenology models, we used spatial temperature data of Switzerland to produce risk maps that can serve as a basis for further studies and decision support