Sustainable strategies for managing weeds are critical to meeting agriculture’s potential to feed the world’s population while conserving the ecosystems and biodiversity on which we depend. The dominant paradigm of weed management in developed countries is currently founded on the two principal tools of herbicides and tillage to remove weeds. However, evidence of negative environmental impacts from both tools is growing, and herbicide resistance is increasingly prevalent. These challenges emerge from a lack of attention to how weeds interact with and are regulated by the agroecosystem as a whole. Novel technological tools proposed for weed control, such as new herbicides, gene editing, and seed destructors, do not address these systemic challenges and thus are unlikely to provide truly sustainable solutions. Combining multiple tools and techniques in an Integrated Weed Management strategy is a step forward, but many integrated strategies still remain overly reliant on too few tools. In contrast, advances in weed ecology are revealing a wealth of options to manage weeds at the agroecosystem level that, rather than aiming to eradicate weeds, act to regulate populations to limit their negative impacts while conserving diversity. Here, we review the current state of knowledge in weed ecology and identify how this can be translated into practical weed management. The major points are the following: (1) the diversity and type of crops, management actions and limiting resources can be manipulated to limit weed competitiveness while promoting weed diversity; (2) in contrast to technological tools, ecological approaches to weed management tend to be synergistic with other agroecosystem functions; and (3) there are many existing practices compatible with this approach that could be integrated into current systems, alongside new options to explore. Overall, this review demonstrates that integrating systems-level ecological thinking into agronomic decision-making offers the best route to achieving sustainable weed management.

Due to the steadily increasing number of putative herbicide-resistant weed populations, the demand for rapid in-season tests is rising. In this study, we introduce a new quantitative herbicide-resistance test system based on chlorophyll fluorescence imaging analysis of photosynthesis-related parameters. Susceptible and herbicide-resistant populations of Alopecurus myosuroides (black-grass) were cultivated in multiwell tissue culture plates containing nutrient agar and different dosages of fenoxaprop-P-ethyl and mesosulfu-ron+iodosulfuron. The maximum quantum efficiency of the PSII was measured 3 h after transplanting (HAT) and then for seven days every 24 h. Data of maximum quantum efficiency of the PSII were compared with standard whole-plant pot tests and molecular tests for target-site mutations. It was possible to fit dose-response curves and calculate corresponding resistance factors for ED90 for all populations tested using the chlorophyll fluorescence imaging. It was possible to distinguish between resistant and susceptible populations. The results of the chlorophyll fluorescence imaging corresponded well with the standard whole-plant pot tests in the glasshouse. However, populations with proved target-site mutations did not differ from other herbicide-resistant populations in the maximum quantum efficiency values of the PSII. We conclude that the chlorophyll fluorescence imaging provides reliable data on herbicide resistance for both modes of action tested in a shorter time and using less space, compared with standard whole-plant pot tests in the glasshouse.

Recently, the acetohydroxyacid synthase (AHAS) amino acid substitution Asp376Glu was detected in a Lolium perenne population originating in France. This is the first documented occurrence of the Asp376Glu single-nucleotide polymorphism in a Lolium species. The effects on herbicide efficacy and plant fitness are presented. Separation of the original population into different genetic subgroups allowed the comparison of different L. perenne AHAS genotypes according to their susceptibility to AHAS-inhibiting herbicides. Root and shoot biomass accumulation as well as tiller production was analysed for resistant and sensitive populations. Genotype-specific AHAS activity and inhibition were studied in vitro, using recombinant Arabidopsis thaliana DNA. Plants expressing the AHAS Asp376Glu genotype were resistant against mesosulfuron ? iodosulfuron, pyroxsulam and propoxycarbazone. To imazamox, reduced susceptibility for dosages below 140 g a.i. ha -1 was observed. In the absence of herbicide, no significant impact of the Asp376Glu genotype on shoot biomass and tiller accumulation could be observed, whereas root biomass of the Asp376Glu genotype was significantly reduced by 68 % compared to the AHAS genetic wild type. The AHAS enzyme study revealed reduced AHAS enzyme rate of 48 % for the Asp376Glu genotype compared to the AHAS genetic wild type. This study highlights the role of the amino acid exchange on resistance profile against the most relevant AHAS-inhibiting herbicides. First indications were found that fitness of the Asp376Glu genotype is hampered.

The sustainable management of unwanted vegetation in agricultural fields through integrated weed control strategies requires detailed knowledge about the maternal formation of primary seed dormancy, to support the prediction of seedling emergence dynamics. This knowledge is decisive for the timing of crop sowing and nonchemical weed control measures. Studies in controlled environments have already demonstrated that thermal conditions and, to some extent, water availability during seed set and maturation has an impact on the level of dormancy. However, it is still unclear if this applies also under field conditions, where environmental stressors and their timing are more variable. We address this question for Alopecurus myosuroides in south‐western Sweden. We quantified the effects of cumulated temperature and precipitation as well as soil water potential during the reproductive growth phase of A myosuroides on primary seed dormancy under field conditions. Empirical models differing in focal time intervals and, in case of soil water potential, focal soil depths were compared regarding their predictive power. The highest predictive power for the level of primary dormancy of A. myosuroides seeds was found for a two‐factorial linear model containing air temperature sum between 0 and 7 days before peak seed shedding as well as the number of days with soil water potential below field capacity between 7 and 35 days before peak seed shedding. For soil water potential, it was found that only the top 10 cm soil layer is of relevance, which is in line with the shallow root architecture of A. myosuroides. We conclude that for this species the level of dormancy depends on the magnitude and timing of temperature and water availability during the reproductive growth phase. Water availability appears to be more important during maternal environmental perception and temperature during zygotic environmental perception.