Temporal and spatial variability results of fungicide use in winter wheat (Triticum aestivum L.) recommend region-specific fungicide reduction targets

To address the imperative for sustainable agricultural practices and navigate the ongoing debate on the proposed Sustainable Use of Pesticides Regulation (SUR), it is crucial to understand pesticide application and formulate strategies that meet farmers’ requirements. This study provides a detailed analysis using data on chemical plant protection measures for winter wheat ( Triticum aestivum L.) taken from 40 farms across four regions in northern Germany between 2010 and 2018. These high-yield winter wheat regions correspond to administrative districts characterized by distinct regional patterns. This study analysed on-farm fungicide use intensity, described as treatment frequency (TF) and treatment frequency index (TFI), for each region. Linear mixed-effects models examined the effect of fungicide use intensity and management factors, including region, farm, year, soil, previous crop, and the growth stage at which fungicides were applied, on winter wheat yield. Major temporal and regional variations in fungicide use were identified. Temporal variability in fungicide use was mainly attributed to climatic factors. Regional contrasts along north-south and west-east axes were observed, with the two northern regions having a higher fungicide use intensity than their more southerly counterparts and the two western regions having a higher fungicide use intensity than their more easterly counterparts. The results concerning the application of fungicides throughout the entire phenological growth stages (BBCH) of winter wheat indicated the greatest diversity of fungicide products used at around BBCH 31 and 61. The two northern regions showed higher frequencies of usage and a larger number of different fungicide products. Based on the on-farm data, this study determined that the regional-level baseline for a potential 50 % reduction in TFI either exceeded or fell short of the nationally recommended reference baseline generated from JKI reference data. This presents some regions with challenges if they are to meet the consistent national objective of decreasing fungicide usage. These results highlight the importance of customising fungicide reduction targets according to temporal and regional factors, and demanding a comprehensive approach that incorporates scientific innovations, practical production methods, and policy and economic aspects. While this research uses Germany as a case study, the implications of region-specific fungicide reduction targets will also be relevant for other European member states in supporting efforts to achieve sustainable winter wheat production across diverse regions. • Nine-year long-term data analysis combined with commercial model data provided a comprehensive overview of winter wheat fungicide use patterns. • Temporal and regional variations in fungicide use on winter wheat were observed. Compared with more southern regions in Germany, the northern regions exhibited higher fungicide use intensity and greater diversity in the fungicide products applied. • On-farm data showed that fungicide use intensity and geographic, temporal and management factors, e.g., region, tillage and previous crop, significantly influenced winter wheat yield. • Tailored fungicide reduction strategies are necessary to achieve sustainable winter wheat production at European and global levels, using Germany as an example.