Perennial weeds reproduce both sexually, by setting seeds, and by clonal propagules (Håkansson, 2003). Creeping perennials ensure their lifeforms by subterranean storage organs, like roots, rhizomes or stolons (Anderson, 1999). Their clonal systems facilitate survival and spatial spread in arable fields by sprouting from these vegetative propagules (Harper, 1979; Navas and Goulard, 1991). Classified as geophytes that regenerate their above-ground plant biomass from subterranean sources, creeping perennial weeds may in general occur in different agroecosystems. Farming systems suffer from perennial weed infestations (Turner et al., 2007; Riemens et al., 2010; DeDecker et al., 2014). Some species are strongly adapted to arable land frequently disturbed (Tørresen et al., 2003; Bergkvist et al., 2017; Brandsæter et al., 2017).

The weediness and persistence of perennial weeds mainly depend on their vegetative growth and creeping root system (Håkansson, 1982) which allow the species to store nutritive elements and remain alive for several years (Buhler, 1994). For this reason, perennial weed management strategies require a multi-year approach, including specific preventive measures (e.g., crop rotation), cultural methods (e.g., competitive crops and varieties), and direct weed control tactics (e.g., use of herbicides, stubble management, mowing), which depend on the farm type and farm equipment (Mohler et al., 2021). Perennial weed control is one of the main challenges in organic farming (Bond and Grundy, 2001; Turner et al., 2007), more than in conventional farming. In organic farming systems, preventing perennial weeds by tillage practices, precisely displayed at the adequate moment, is important as synthetic chemical herbicides for weed control are excluded (Gruber et al., 2012). Cultural methods are specially appropriated to minimize gaps in which perennials may proliferate uncontrollably (Melander et al., 2012). Closing gaps in competition by subsidiary crops, e.g., cover crops, catch crops, either under-sown in the main crop or established after harvest, both for the purpose to perform competition in the period between main crops, is an important strategy to manage creeping perennial weeds (Vanhala et al., 2006; Bergkvist et al., 2010; Ringselle et al., 2015; Thomsen et al., 2015; Kolberg et al., 2018).

Such a systemic approach is different to the common trend in conventional farming where perennial weed control commonly includes direct control tactics (Harker and O'Donovan, 2013; Favrelière et al., 2020). Herbicides are central in the conventional approach to manage perennial weeds (McErlich and Boydston, 2014), while inversion tillage by a mouldboard plough and stubble cultivation in the intercropping period are crucial for non-chemical weed control (Brandsæter et al., 2017).

In conservation agriculture, the farmers rely on the same weed management practices as in conventional tillage systems but eliminate most or all of the tillage practices. Those inverting the soil are completely omitted. By reducing tillage kind, depth and frequency in conservation farming, perennial weeds became more prevalent than under conventional tillage systems (Pekrun and Claupein, 2004). Likely, conservation farming is depending much more on cultural (e.g., crop rotation, competitive cultivars, cover crops) and chemical control options (Soane et al., 2012). Indeed, conservation farmers design their cropping systems around the use of the non-selective active ingredient glyphosate (Andert et al., 2018; Pardo and Martínez, 2019; Beckie et al., 2020). Across European countries, one third of the acreage of annual cropping systems and half of the acreage of perennial tree crops are annually sprayed with glyphosate (data from 2013-2017, Antier et al., 2020). In Germany, detailed analyses of on-farm application patterns revealed that glyphosate was used for stubble and pre-sowing application on 34.0% of all fields (Andert et al., 2018). Among the French DEPHY farms (network, which represents more than 3,000 farms) with arable crops, 59% used glyphosate regularly or occasionally (Lapierre et al., 2019).

While the use of glyphosate remains by far the most effective practice for controlling perennial weeds in conventional and conservation farming, reduction strategies and acceptable alternatives are urgently required as glyphosate is expected to be increasingly restricted or even banned in Europe (Fogliatto et al., 2020; Kudsk and Mathiassen, 2020; Tataridas et al., 2022; Triantafyllidis et al., 2023). More and better agro-ecological weed management was likewise the specific goal of the European Directive 2009/128/EC on sustainable use of pesticides. Experimental results prove the efficacy of non-chemical control of perennial weeds, e.g., mechanical cutting (Bond and Grundy, 2001; Tiley, 2010), repeated mowing and hoeing (Graglia et al., 2006; Brandsæter et al., 2012; Bergkvist et al., 2017), stubble cultivation (Pekrun and Claupein, 2004), inversion tillage (Thomsen et al., 2015; Brandsæter et al., 2017), competition by cover crops (Vanhala et al., 2006; Kolberg et al., 2018) and vertical and horizontal cutting with minimum soil disturbance (Ringselle et al., 2018; Brandsæter et al., 2020).

Here, we present a survey to gain knowledge about farmers’ perennial weed management on-farm. We analyzed data from a survey among farmers in Northern France and Eastern Germany. We chose these study regions because the restriction or outright ban of the common active ingredient glyphosate is planned or occurring in France and Germany (Tosun et al., 2019; Beckie et al., 2020; Leonelli, 2023).

The 2017 EU-wide renewal of approval of glyphosate (currently approved until 15 December 2023) has caused considerable discontent among Member States, triggering the enactment of several national or regional measures. Despite Glyphosate was the most widely used herbicide active substance (9,700 tonnes in 2018 according to the Ministry of Ecological Transition and Solidarity 2019), France was the first country to announce an intention to ban glyphosate within three years (2017-20) (Kinniburgh, 2023). Nevertheless, instead of instituting a full ban on glyphosate in 2020, France merely announced new regulations which further restrict use authorizations for products containing glyphosate. In general though, France was the first European country with an overall pesticide reduction target of 50% (Ecophyto plan for 2018, proposed by the Grenelle Environment Forum in 2007), equivalent to the EU’s 2030 goal under the Farm to Fork Strategy (European Commission, 2020). Even France has failed to reduce pesticide use (Hossard et al., 2017), the policy adopted by the country (Ecophyto II and II+ plans for 2025) promotes the agro-ecological transition of its farms (Chauvel et al., 2022). Likewise, the German government’s Arable Farming Strategy 2035 sets out the clear direction for the reduction of pesticides (Bundesministerium für Ernährung und Landwirtschaft, 2021a). Starting 2020, the German government has also implemented a glyphosate reduction strategy and proposed to ban the use of plant protection products containing glyphosate in Germany after December 31, 2023 (Bundesministerium für Ernährung und Landwirtschaft, 2021b).

At the same time, many European farmers and farmers’ unions are vigorously opposed to the ban of glyphosate (Bjørnåvold et al., 2023). It is specially challenging for no-till agriculture because these systems can be difficult to set up and lack sustainable solutions for weed management without such type of herbicides (Kassam, 2019). Without glyphosate, fundamental changes in farming practices, and perennial weeds in particular are expected (Kudsk and Mathiassen, 2020) and a systemic approach is needed to design no herbicides systems (Chikowo et al., 2009; Reboud et al., 2019).

The objective of this study was to explore the practical experience of farmers. We wanted to answer the following questions:

The analyses focus the regional and farm type level to see whether differences in production conditions and systems have an influence on farmers’ perceptions and experiences of perennial weeds and their control. Both regions chosen are characterized by arable cropping and include farms of different types.

This study analysed farmers’ perceptions and experiences on perennial weeds and their control in Northern France and Eastern Germany. Opinion surveys offer comprehensive pictures of farmers’ appraisements (Ulber and Rissel, 2018; Andert et al., 2019; Lanker et al., 2020; Matousek et al., 2022).

We aimed to include organic, conservation and conventional farmers from two European countries into our study in order to reveal the range of variations in perennial weed management.

We found a high level of awareness for perennial weeds. On average, 80.0% of Northern French farmers and 65.9% of Eastern German farmers revealed present concerns about perennial weeds ( Table 6 ). Both, Northern French and Eastern German farmers perceived perennial weeds as more damaging to crop production than other pests.

Sample sizes in our study differed between the study regions Northern France and Eastern Germany. The questionnaire-based survey among Eastern German farmers allowed the acquisition of a larger sample size with lower effort compared to the French survey. A potential limitation of the present study is the sample size of participants (Andrade, 2020); increasing the number of respondents to consolidate our findings would further support the study results. Matousek et al. (2022), describe that the recruitment of participants is effortful because many farmers are expected to be blamed for using glyphosate-based herbicides, and thus, were probably sceptical about the related perennial weed control topic. Therefore, our results provide unique indications for future perennial weed management in Europe. Another limitation of our study is that voluntary recruiting participant in the study region Eastern Germany can cause an unwanted pre-selection of participants. This is a general weakness in questionnaire-based samples (Wu et al., 2022). Pre-selecting the Northern French farmers’ by the criterion that they had to manage perennial weeds on their fields, on the other hand may have overestimated the creeping perennial weeds and their need to control. Nevertheless, the findings of this study offer valuable new insight how farmers perceive and control perennial weeds currently and in the future. Moreover, because of their concern about the perennial weeds, farmers could more easily provide a sound advice and share their expertise on solutions to manage the weeds, by soil disturbance or cover crops.

The ability to reproduce vegetatively is a unique characteristic among arable weeds that promotes the survival of perennial species over winters, dry seasons or other unfavorable periods to growth (Håkansson, 1982). Farmers’ awareness of perennial weeds and their suitable control tactics are especially important because the infestations are likely to spread rapidly, and have negative impact lasting several years if effective management is not undertaken. Overall, 100% of the surveyed farmers listed C. arvense as the most important perennial weed species, and more than 50% of farmer participants stated Rumex spp. infestations ( Figure 4 ). The two species are troublesome weeds in both arable lands and grasslands (mainly pastures), but Rumex spp. are also early colonizers of many disturbed areas (Zaller, 2004; Favrelière et al., 2020). Interestingly, field infestations of E. repens are most prominent among farmers in Eastern Germany. Probably, E. repens infestations are favored by common reduced tillage, cereal-dominated crop rotations and high-intensive nitrogen fertilization in this region (Andreasen and Skovgaard, 2009; Andert et al., 2016; Ringselle et al., 2020). Northern French farmers more often reported S. arvensis infestations. This species is especially known and problematic in Nordic countries in arable crops and, to some extent, in grasslands (Vanhala et al., 2006; Tørresen et al., 2010; Andersson et al., 2013). Whilst, temperature and concentration of CO₂ are increasing globally, S. arvensis reacts with higher biomass and reproduction (Tørresen et al., 2019). For this reason, this species is a candidate to profit from climate change (Tørresen et al., 2019), and thus, might potentially spread to other regions.

One of the most interesting results of our study is that farmers in Eastern Germany are more concerned about future perennial weed problems than those in Northern France. We attribute the differences in farmers’ concerns to regional production differences in our study. The farms were significantly smaller and crop rotations were longer in Northern France than in Eastern Germany ( Table 4 ). Perennial weed control of Eastern German farmers is mainly based on chemical herbicide use, while inversion soil disturbance and competition by cover crops is widely used by the surveyed Northern French farmers ( Figure 4 ). As introduced, disturbance and competition are two important processes which are used to manage creeping perennials weeds non-chemically. Obviously, farmers in Northern France are aware of these agro-ecological weed control tools, designing their cropping systems to be less dependent on herbicides. These cropping systems are expected to be more resilient for future farming.

Farmers in the two regions are differently concerned about perennial weeds in the future. In each region, however, farmers’ perceptions of future perennial weed problems were mainly explained by differences between the farm types ( Figure 2 ). The reasons for farmers’ future concerns are fairly obvious and connected to the farming system. In both regions, conservation and conventional farmers heavily rely on herbicides for perennial weed control ( Figure 1 ). Indeed, Andert et al. (2022) observed that C. arvense was more common in fields less frequently treated with glyphosate. Currently, there is a lack of effective alternatives to glyphosate to manage conservation fields without disturbing the soil in the long term (Nichols et al., 2015), because even direct perennial weed control by selective herbicides might be less effective than in the past decades. Tavaziva et al. (2019) stated that 100% of the recommended MCPA (2-methyl-4-chlorophenoxyacetic acid) dosage is required to obtain the strongest control of C. arvense. This finding is in accordance with results from a study of C. arvense and S. arvensis where less reduced herbicide doses of MCPA gave an increase in above-ground biomass as compared with recommended dose (Fogelfors and Lundkvist, 2008).

The demand for reducing both selective and non-selective herbicides will increase the complexity of farm management and decision-making (Rossi et al., 2012; Jussaume et al., 2022) for perennial weed management in conservation and conventional farming. However, as expected and already described by other authors, perennial weed control is a major concern for organic farmers (Turner et al., 2007; Melander et al., 2012; Brandsæter et al., 2020). Likewise, in Northern France and Eastern Germany, organic farmers are concerned about future perennial weed problems ( Table 6 ), as direct physical weeding techniques, like harrowing, inter-row hoeing, brushing and even flaming the crops, have not shown to be effective to control perennials (Melander et al., 2005). Indeed, creeping perennial weeds might threaten the future of organic cereal production (Salonen et al., 2013; McErlich and Boydston, 2014), especially under reduced-tillage (Armengot et al., 2015). Thus, controlling perennial weed is a continuous challenge for farms of all types.

While inversion tillage is of paramount importance to reduce perennial weed infestations, many farmers want to reduce the intensive soil tillage as it consumes much energy and labor costs, compacts the ground and diminishes soil biological activities (Cooper et al., 2016; Zikeli and Gruber, 2017). New ways of applying belowground disturbance without turning the soil include mechanical tools which cut roots/rhizomes horizontally (linked to weed species with deep root systems) or vertically (linked to weed species with shallow root systems) (Thomsen et al., 2015; Brandsæter et al., 2017; Ringselle et al., 2018; Brandsæter et al., 2020; Weigel and Gerowitt, 2022). These techniques may assist to overcome the trade-off between perennial weed control and reduced tillage. As cover crops are already established in farming systems, it will be promising to further develop control tactics which combine non-inversion tillage practices and cover crops. Developing agro-ecological weed management techniques and successfully implementing these in farming systems for consistent perennial weed control will be important for long-term viability of agricultural systems. Organic farmers could help in the way to design new systems. Long-term experiments on weed management demonstrate that it is possible to reduce herbicides dependencies, if a systemic and agroecological approach is engaged (Deytieux et al., 2012; Lechenet et al., 2017). Indeed, the unique characteristics of perennial weeds complicate the task of reducing or even eliminating the use of herbicides. However, the implementation of non-chemical perennial weed control might become an example to transform agriculture, shaping the approach to ensuring food security and fostering sustainable methods of production (Vanbergen et al., 2020).

Farmers in Northern France and Eastern Germany are concerned about perennial weeds in the future. The demand for reducing herbicides will increase the complexity of perennial weed control for conservation and conventional farming. The outright ban of glyphosate could completely challenge the development of conservation agriculture in which the management of perennial weeds highly depends on this active ingredient. Up to now, perennial weed control was especially a major obstacle for organic farming. However, this is expected to change considerably in the future, because perennial weed control might become a challenge to all farmers.

The ability to reproduce vegetatively of those weeds promotes them an uncredible capability to survive over winters, dry seasons or other unfavorable periods and therefore they are a sort of key indicators to assess the successfulness of “no-less herbicides systems”. These specific weeds may give the chance to farmers-advisers to re-design their crop management in a systemic way, all the more as “easy herbicides solutions” do not exist anymore. Therefore, integrating and optimizing non-chemical weed control alternatives is required in all farming systems. We conclude, that perennial weeds as ‘difficult-to-control weeds’ should take a special position in National Action Plans of the EU Member States. Research activities should provide all farmers and extension services with novel and profitable perennial weed management practices. Moreover, the EU countries should long-term monitor perennial weeds and the consequences of their control.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Conceptualization, SA, MV-M, and BG; Data curation, MH and JG; Formal analysis, SA, MH, and JG; Funding acquisition, SA, MV-M, and BG; Supervision, MV-M and BG; Validation, SA and JG; Visualization, SA and MH; Writing—original draft, SA; Writing—review and editing, SA, JG, MV-M, and BG. All authors contributed to the article and approved the submitted version.