Have we given up on IPM? Lessons from the Nordic cereal frontier - a critical review

Integrated Pest Management (IPM) promises a sophisticated integration of biological, cultural, genetic, and chemical tactics to manage pests sustainably (Kogan, 1998;Ehler, 2006). This vision remains central to modern crop protection discourse (Barzman et al., 2015). However, the translation of this ideal into widespread practice has been uneven, especially in large-scale cereal production. The Nordic region presents a compelling paradox: despite strong scientific capacity and ambitious sustainability goals, agriculture continues to rely heavily on prophylactic chemical treatments. Current trends illustrate this disconnect (Figure 1A,B).While the EU aims for a 50% reduction in pesticide use, sales across the continent have plateaued (Figure 1A), and in Sweden, fungicide use remains stubbornly high, fluctuating with seasonal weather rather than showing a structural decline (Figure 1B). We contend that this discrepancy is not rooted in a lack of will but in formidable biophysical realities. In high-latitude cereal systems, the classical IPM model encounters a structural ceiling imposed by adaptation constraints, compressed seasonal timelines, and an incomplete decision-support infrastructure (Olesen et al., 2011;Peltonen-Sainio et al., 2016). Recent assessments also highlight how climate variability intensifies disease risk windows and complicates timing-sensitive interventions in northern European cereal systems (Newton, 2024;Lahlali et al., 2024). In the following sections, we therefore use a small set of representative examples, including polycyclic foliar diseases in cereals and aphid vectors of BYDV, to illustrate how specific biological constraints shape the feasibility and design of IPM in Nordic systems.In this paper, we use four related terms with specific meanings that build on established IPM literature. IPM is understood as a framework for systems-based crop protection that integrates biological, cultural, physical and chemical tactics to maintain pest populations below economically damaging thresholds while minimizing environmental risks, as formalized by the Food and Agriculture Organization of the United Nations (FAO) and the European Union (EU) (FAO, 2022; EU Directive 2009/128/EC). Within this framework, an IPM strategy denotes the decision logic governing how tactics are sequenced and combined over time. For example, prioritizing host resistance and cultural practices, with chemical or biological interventions deployed only when monitored pest pressure exceeds predefined action thresholds (Kogan, 1998; Barzman et al., 2015). We use IPM levers to describe the principal tactic classes available for manipulation in practice: cultivar selection, crop rotation, biological control agents, cultural methods, and pesticide application timing (Ehler, 2006;Parlevliet and Zadoks, 1977). Finally, the IPM network refers to the emergent system arising from interactions among multiple levers and pest complexes, encompassing both vertical integration of tactics within individual pesthost systems and horizontal integration across multiple pest groups; a concept central to recent critiques of insufficient integration in contemporary IPM implementation (Barzman et al., 2015;Stenberg, 2017).The theoretical power of IPM lies in its multi-lever approach, combining host resistance, cultural practices, biological control, and monitoring to keep pest pressure below economic thresholds. In northern cereal systems, however, several of these levers are inherently compromised. While IPM principles theoretically apply to all pest classes, the specific constraints and solutions discussed below (and summarized in Table 1) primarily reflect the region's most pressing challenges: polycyclic fungal pathogens (such as Zymoseptoria and Puccinia spp.) and insect vectors of viral diseases (such as Rhopalosiphum padi). These fungal and vector systems are not treated as comprehensive case studies here, but as illustrative examples of distinct bottlenecks, such as high regional inoculum for polycyclic foliar diseases and phenological mismatch between aphid flights, virus transmission, and natural enemy activity in spring cerealsEffective IPM leverages host diversity through the rotation or mixing of cultivars with complementary resistance profiles. However, in countries like Sweden, the harsh climate, with its specific photoperiod and temperature demands, significantly narrows the pool of adapted cultivars for spring barley, oats, and wheat. The dominant varieties often share similar vulnerabilities, diminishing the effectiveness of resistance rotation strategies. This genetic bottleneck allows polycyclic foliar pathogens, such as leaf blotch in wheat and net blotch in barley, to escalate rapidly under high regional inoculum pressure, even with careful variety selection (Jalli et al., 2020). Continued emergence of fungicide resistance and shifts in pathogen virulence spectra underscore the need for diversified resistance portfolios and coordinated stewardship (FRAG-UK, 2025; Minadakis et al., 2025).Cultural tactics are similarly constrained by climatic and phenological limits. Short seasons compress sowing and harvesting into tight windows, making practices like delayed sowing to avoid early infection a high-risk strategy that can lead to significant yield penalties. Cover crops and green manures often struggle to accumulate enough biomass to effectively alter soilborne disease dynamics, and the cool, slow decomposition of crop residues allows pathogens like Zymoseptoria and Fusarium to persist between seasons. While the agronomic logic of these practices is sound, their efficacy and feasibility are greatly diminished in these environments (Aronsson et al., 2016;Peltonen-Sainio et al., 2016).Biological control agents are frequently out of phase with pest and pathogen life cycles. As illustrated in the Nordic spring barley model (Figure 1C), natural enemies of cereal aphids, for instance, often build up their populations too late to prevent the initial flights of Rhopalosiphum padi and Sitobion avenae, leaving young crops vulnerable to Barley Yellow Dwarf Virus. We highlight this aphid-BYDV system because its phenology is relatively well characterized in Nordic spring cereals and thus offers a concrete, data-informed example of the broader timing mismatch that also constrains other biological control opportunities. Similarly, many microbial antagonists show inconsistent performance at the low temperatures typical of Nordic springs.While research into cold-tolerant strains is ongoing, field-scale reliability remains a significant hurdle under typical Nordic spring conditions (Smera et al., 2021). Furthermore, the ecological dependency of biological control efficacy greatly reduces its role in disease management, compounded by pathogen adaptation problems that, while potentially as severe as those affecting chemical control, receive considerably less attention and research focus (He et al., 2021;Dehbi et al., 2023). This dual challenge of environmental synchronization and pathogen evolution further constrains the practical deployment of biocontrol strategies in Nordic cereal systems. The development of seed-applied endophytes, antagonistic microbial consortia, and residuedecomposing microbiomes selected for their ability to thrive in cool conditions is a promising frontier, but current results are highly context dependent. Field reliability is constrained by several failure modes, including reduced activity at low temperatures, mismatches in timing between application, pathogen infection and crop growth, formulation stability, and the ability of introduced strains to establish in resident microbiomes (Dehbi et al., 2023;Newton, 2024).These approaches can therefore complement other IPM tactics only when their performance has been validated through multi-year, on-farm trials that capture the variability of short Nordic seasons and management regimes. Beyond these biological constraints, commercial development of biocontrol products faces a structural economic barrier in Nordic systems: the region represents a relatively small market compared to major cereal-producing areas in southern and central Europe, North America, and Asia. Consequently, commercial BCA formulations are typically optimized for persistence, shelf stability, and efficacy under the temperature and moisture regimes characteristic of these larger markets, rather than for the cooler, shorter growing seasons of northern latitudes (Alabouvette et al., 2009;Parnell et al., 2016;Köhl et al., 2019). This market-driven mismatch between formulation design and local environmental conditions compounds the inherent biological challenges, rendering many otherwise-promising BCAs unreliable under Nordic field conditions unless region-specific development programs are pursued; an investment that remains economically marginal for most commercial producers.A lack of locally validated data hinders risk-based decision-making. Many forecasting models used in advisory systems were developed for different climates and often fail to accurately predict infection dynamics under Nordic weather patterns. In the absence of reliable, local risk indicators, prophylactic spraying becomes the default, economically rational choice for many growers. Although Nordic-tuned models and surveillance systems are being developed and refined, their widespread implementation is still a work in progress (Folkedal and Brevig, 2003;Jørgensen et al., 2020;Hjelkrem et al., 2021). Recent advances in spatial decision-support systems and precision agriculture platforms demonstrate potential for field-specific risk advisories, although adoption barriers persist in advisory pipelines and data integration (Yi et al., 2024;Lanucara et al., 2024).Crop rotation, often the cornerstone of IPM, has reduced leverage in regions where break crops are agronomically or economically challenging. In much of Sweden and Finland, agroclimatic conditions and market factors limit the cultivation of grain legumes and oilseeds. Marketing challenges for alternative crops create additional barriers, as farmers may struggle to find reliable buyers and stable prices for non-cereal crops. Furthermore, transitioning to new crops requires substantial investment in specialized machinery and equipment, alongside the acquisition of new agronomic knowledge and management skills for crops that farmers may be less familiar with growing. These economic and technical barriers compound the agronomic limitations. Recent studies indicate that while diversified rotations improve yields and ecosystem services in many environments, the magnitude and feasibility of such benefits are ). As a result, the knowledge base available to operationalize IPM 2.0 is structurally richer for some disease systems than for most arthropod pests, and this asymmetry has to be acknowledged in any realistic redesign of IPM.Acknowledging these limitations allows us to move beyond an idealized IPM framework and design a more pragmatic approach: IPM 2.0. Unlike the classical model, which often assumes a fully functional toolkit of rotational and biological levers, IPM 2.0 in the Nordic context is defined as a system-redesign focused on compensatory resilience. It abandons the universal application of IPM in favor of a functional subset of tactics-specifically intra-crop diversity and digital precision-that collectively compensate for the lack of rotation and biological control options. At the same time, IPM 2.0 must explicitly integrate context-dependent ecology and genetics, which can shift roles between 'pest' and 'ally' as host genotype, climate and management change (Table 2).A practical example is wheat leaf blotch management in the Nordic-Baltic region. Under current practice, fungicide use is often guided by coarse calendar windows and visual scouting, with limited integration of cultivar resistance profiles or modelled risk, leading to both under-and over-treatment in different years (Jalli et al., 2020;Hjelkrem et al., 2021). Under an IPM 2.0 approach, mixtures of varieties with quantitative resistance, combined with locally calibrated leaf blotch DSS and spore-based surveillance, would allow growers to adjust both the need for and timing of fungicide applications at field scale (Jørgensen et al., 2020;Hjelkrem et al., 2021). This shift does not eliminate chemical control, but reframes it as a targeted, model-informed intervention embedded within a more diverse and resilient cropping system (Parlevliet and Zadoks, 1977;Brown, 2015;Rimbaud et al., 2019).For insect vectors such as cereal aphids transmitting BYDV, the transformation is necessarily more incremental because the empirical base is thinner. At present, many decisions in Nordic spring cereals default to prophylactic early-season insecticide use whenever aphids are observed or expected, in the absence of robust, locally validated thresholds or DSS (Larsson, 2005;Ghita, 2015;Sigvald, 2015). An IPM 2.0 scenario would combine existing phenology and flight information, simple field monitoring, and emerging BYDV risk tools to focus insecticide interventions on years and locations with demonstrably high risk, while omitting treatments when monitored risk is low (IPM Decisions, 2024; IPM Decisions BYDV DSS factsheet). Here, the same pillars (diversified host backgrounds where feasible, higherresolution surveillance, and participatory evaluation) still apply, but the operational framework is built around a smaller and more uncertain dataset than for fungal leaf blotch. Thus, a redesigned IPM 2.0 for constrained environments must prioritize the following:When diversification between crops is limited, we must focus on diversification within crops.Cultivar mixtures and multiline blends, which combine varieties with similar phenology but different resistance profiles, can effectively slow epidemics and the evolution of pathogen virulence (Yang et al., 2019;Huang et al., 2024). For Swedish spring barley and oats, where adapted cultivar choice is narrow, developing mixture-ready lines would embed IPM at the seed level, shifting from a reactive to a proactive strategy. This is particularly relevant for diseases like crown rust in oats, where even modest, stable reductions in pathogen reproduction can provide significant protection over a short growing season (Østergård, 2005 The credibility of IPM hinges on replacing risk-averse, prophylactic spraying with data-driven interventions. This transition relies on the integration of precision agriculture technologies (specifically the Internet of Things (IoT), automated surveillance, and cloud-computing), into cereal disease management. Current forecasting models often fail because they lack local granularity. However, the emerging generation of Spatial Decision Support Systems (SDSS) offers a solution by processing real-time environmental data to generate site-specific risk advisories. Recent reviews of precision agriculture emphasize that shifting from regional forecasts to field-level predictions is essential for reducing pesticide loads in volatile climates (Lanucara et al., 2024;Yi et al., 2024). Where basic phenological and flight data exist for key insect vectors (for example, cereal aphids involved in BYDV transmission) these can be integrated alongside pathogen risk models to design unified, field-specific decision around early-season the Nordic DSS must be validated under local climates and cropping systems, not only calibrated This multi-year, that models both where interventions are and where they can be and that yield We need to ecological that is at low The development of seed-applied endophytes, antagonistic microbial consortia, and microbiomes selected for their ability to thrive in cool conditions is a promising frontier, but current results are highly context dependent. Field reliability is constrained by several failure modes, including reduced activity at low temperatures, mismatches in timing between application, pathogen infection and crop growth, formulation stability, and the ability of introduced strains to establish in resident microbiomes (Dehbi et al., 2023;Newton, 2024).These approaches can therefore complement other IPM tactics only when their performance has been validated through multi-year, on-farm trials that capture the variability of short Nordic seasons and management work with the fungal biocontrol both the potential and the of microbial in IPM as summarized in Table such that an from may fail to establish or in southern Finland, or even when to the same crop et al., et al., 2020). these underscore that ecological host genotype, resident and temperature is central to BCA performance in IPM and that, chemical are decision-support tools to predict which will be both and 2.0 implementation in Nordic cereal systems requires through participatory on-farm research that the of multiple tactics under commercial Unlike this IPM as an system where and performance and decision on observed (Kogan, 1998; Barzman et al., examples demonstrate this in In on-farm trials coordinated through of have cultivar mixtures combined with fungicide applications across diverse environments, both yield and where mixtures under specific disease for regional (Jørgensen et al., et al., 2020). Similarly, Swedish field trials seed-applied biocontrol agents for cereal pathogens have both disease and to environmental the empirical for deployment windows and management practices et al., 2016). These participatory that as thresholds for Zymoseptoria on cultivar resistance profiles or BYDV risk models for regional aphid from field rather than theoretical (Jørgensen et al., 2020;Hjelkrem et al., to this is of both and which allows the research to context-dependent constraints and avoid from site-specific results et al., et al., 2024). For instance, of reduced fungicide programs in spring barley that while cultivar resistance delayed economic thresholds still intervention in the of even in systems (Jalli et al., 2020). embedded within regional advisory IPM 2.0 to as a system calibrated to local climate pest pressure dynamics, and risk et al., et al., IPM 2.0 in constrained Nordic cereal systems is defined by prioritizing intra-crop genetic diversity and quantitative resistance as the locally validated surveillance and decision-support systems to and when chemical or biological interventions are and decision thresholds through participatory on-farm (Parlevliet and Zadoks, et al., et al., In practice, this shifts from spraying to risk the and timing of fungicide the of cultivar and the of DSS the season on monitored disease pressure and resistance profiles (Kogan, et al., to widespread DSS adoption hinges on these tools within existing advisory infrastructure and through The this approach: developed through among and integrates disease regional pest monitoring and cultivar resistance to generate field-specific (Folkedal and Brevig, et al., 2021). has been by field that interventions fungicide use by in years yield integration with management used by and model on from advisory (Jørgensen et al., the IPM Decisions has that and DSS use of cropping systems, disease to weather and crop phenology and with to model with on-farm decision constraints (IPM Decisions 2024; et al., 2024;Yi et al., 2024). For Nordic this a integration model where advisory services The Swedish of Agriculture in host DSS data from on-farm weather and monitoring and participatory trials that economic and with regional pest broader et al., this infrastructure must regional a leaf blotch DSS validated for southern Sweden may for northern Finland, where spring phenology and temperature thresholds alter infection windows et al., 2021). through such deployment can IPM 2.0 decision in constrained northern cereal Nordic cereal a in contemporary the classical model assumes a functional toolkit of diverse biological control, and cultural practices that be fully under climatic and agronomic constraints characteristic of northern Short growing crop phenological mismatches between pests and natural and limited economic scale for region-specific biocontrol formulations collectively several IPM levers or This does not a failure of IPM as a but rather that its universal application has ecological and practical in constrained IPM 2.0 for Nordic cereals (Figure offers a framework built on prioritizing intra-crop genetic diversity through cultivar mixtures and quantitative resistance as the for limited rotation locally calibrated surveillance and decision-support systems to prophylactic chemical interventions with and participatory through on-farm trials that both and context-dependent This redesign explicitly that some classical IPM tactics are in Nordic systems, while on the subset of interventions that under of IPM 2.0 implementation are and For insect pest management, the integration of aphid flight monitoring, cultivar resistance and emerging BYDV risk models (IPM Decisions can shift decisions from prophylactic seed treatments to foliar only when monitored aphid pressure and virus risk validated reducing insecticide use in years while protection in seasons 2015). For fungal pathogen management, combining cultivar mixtures with fungicide applications by the reductions in fungicide applications in years yield while intervention capacity when disease pressure (Jørgensen et al., 2020;Hjelkrem et al., 2021). these on resistance quantitative resistance within mixtures pathogen adaptation compared to the functional of both genetic and chemical tools (Parlevliet and Zadoks, et al., these requires IPM 2.0 from concept to operational practice through the adoption in must of DSS under Nordic models both high-risk intervention and where treatments can be services and must integrate validated DSS into existing decision and on-farm that build in risk-based management. this transition requires of alongside when and DSS predictions or when cultivar mixtures fail to the empirical to adjust and the environmental within which tactic remains reliable et al., et al., 2024). IPM not as a but as an data-driven system calibrated to regional constraints, we that pest management remains and even in where classical IPM not This evolution is essential for the of IPM as a IPM principles be in constrained systems through they risk from realities. The Nordic that ecological on functional and within advisory infrastructure can pesticide reductions and system that IPM 2.0 as a evolution of integrated pest management for the climate of modern thresholds and integration into existing advisory infrastructure with on-farm and and with for regional benefits reduced prophylactic pesticide yield stability, resistance through and pest management to regional