ABSTRACT Intraspecific variation in seed germination traits can strongly influence weed persistence and spread, yet its relationship with climate remains poorly resolved. We quantified population‐level variation in germination temperature and water requirements, germination speed and synchrony and seed mass in 12 Alopecurus myosuroides populations from contrasting macroclimatic regions across Europe and West Asia. To minimize maternal environmental effects, all seeds were produced under common‐garden conditions. Germination assays across controlled temperature and water‐potential gradients revealed restricted variation in lower and upper thermal limits, whereas the thermal optimum and water‐potential thresholds varied among populations, with no consistent association with macroclimatic variables. In contrast, germination speed, synchrony and seed mass showed clear geographic structuring: populations from colder and wetter regions germinated faster and more synchronously and produced heavier seeds, whereas populations from warmer and more seasonal regions germinated more slowly, less synchronously and produced smaller seeds. Multivariate analyses confirmed that geographic and climatic variation aligned primarily with germination dynamics and seed mass rather than with hydrothermal germination limits. These results indicate that population differentiation in A. myosuroides is expressed mainly through variation in the timing, coordination and vigour of early establishment rather than through divergence in physiological germination thresholds. For weed management, regional differences in emergence dynamics are therefore likely to influence the effectiveness of cultural and chemical control measures: rapid and synchronous emergence in colder, wetter systems may reduce the efficacy of delayed sowing or stale seedbeds, whereas slower and more asynchronous emergence in warmer, seasonal regions may increase escape from pre‐emergence control. Accounting for population‐level variation in germination dynamics is thus important for designing effective, regionally adapted management strategies for A. myosuroides .
ABSTRACT Arable weeds are a key component of agrobiodiversity, providing both ecosystem services and disservices: while they can reduce crop yields (disservice), they also support higher trophic levels by serving as hosts and providing floral and seed resources that sustain pollinators and natural enemies, alongside additional benefits such as reducing erosion and improving the microclimate (services). Identifying management practices that promote neutral weed communities optimising the trade‐off between their services and disservices, is essential. Organic farming and non‐inversion tillage are promoted for their environmental benefits, but weed management remains a key limitation to wider adoption of reduced tillage (RT) systems. In an organic agronomic trial initiated in 2018, we compared the effect of conventional tillage (CT) resulting in inversion tillage to a maximum depth of 25 cm and RT, defined as non‐inversion tillage at a maximum depth of 10 cm, on weed seed bank and weed standing vegetation, assessing weed species composition, diversity and functional trait‐based potential ecosystem services and disservices calculated by functional trait data extracted from published datasets. Arable weed communities were surveyed during the flowering stage over 3 years (2021–2023) for maize and 2 years (2022–2023) for winter wheat–faba bean. Compared to CT, RT resulted in a denser, richer and more even weed seed bank, without changes in dominant species. In both crops, arable weed standing vegetation under RT showed higher density, species richness and diversity. RT enhanced the potential support of weed communities to pollinators (bees, bumblebees and hoverflies) in maize, while crop‐specific responses were observed in winter wheat–faba bean, with significantly increased support mainly for bumblebees. In both crops, RT consistently increased the potential support to natural enemies (farmland birds, carabid beetles and parasitoid wasps). However, RT also increased the potential competitiveness of weed communities and, in maize, enhanced potential seed bank enrichment, indicating a higher risk of future infestations. As weed communities may still be stabilising following conversion to organic farming, longer‐term monitoring will help confirm whether these patterns persist over time.
ABSTRACT Hirschfeldia incana is a widely distributed Brassicaceae species that has become a weed in temperate cropping systems worldwide. In the Argentine Pampas, its increasing prevalence in winter cereals has raised concerns because acetolactate synthase (ALS)‐inhibiting herbicides are extensively used for broadleaf weed control. This study aimed to characterise the mechanism of resistance to ALS‐inhibiting herbicides in two putatively metsulfuron‐methyl‐resistant H. incana populations and evaluate their cross‐resistance patterns. This work constitutes the first report of ALS‐inhibitor resistance in H. incana and provides the first ALS coding sequences available for this species. Sequencing identified the Trp‐574‐Leu substitution as the only non‐synonymous mutation associated with resistance, while five synonymous polymorphisms distinguished the resistant populations, indicating two distinct resistant haplotypes. Whole‐plant dose–response assays demonstrated broad cross‐resistance to nine herbicides representing the five chemical families of ALS inhibitors, with resistance indices ranging from 10 to 22 and exceeding 31.6 for flucarbazone‐sodium. Cross‐resistance extended to the sulfonylaminocarbonyltriazolinone and pyrimidinyl benzoate families despite the absence of previous field exposure to either group. Molecular docking predicted reduced binding affinity of all evaluated herbicides towards the Trp‐574‐Leu ALS variant, although the magnitude of this effect varied among compounds and was accompanied by herbicide‐specific changes in the ligand‐binding environment, including loss and compensatory reorganisation of noncovalent interactions. These findings demonstrate that selection imposed by a limited number of ALS‐inhibiting herbicide families can compromise the efficacy of chemically distinct ALS inhibitors, highlighting the need for integrated weed management programs based on diversification of herbicide sites of action across crop rotations.
ABSTRACT Due to the increasing emergence of herbicide‐resistant weeds and the pesticide reduction targets of the European Union, new solutions for effective and sustainable chemical weed management are required. Herbicide adjuvants used in combination with reduced herbicide rates may improve herbicide efficacy and facilitate the use of lower‐than‐recommended rates. To investigate the impact of two adjuvants on herbicide efficacy, two herbicides commonly used for weed control in maize, mesotrione and foramsulfuron, were evaluated under field conditions in a two‐year trial. Herbicides were applied solo and as an herbicide mixture without and tank‐mixed with adjuvants (nonionic surfactant and methylated seed oil adjuvant) at a herbicide rate of ¼× and ½×, where 1× represents the recommended field rate. As a comparison, the 1× herbicide and mixture rate was tested without addition of an adjuvant. The majority (90%) of the total weed population was represented by three species. In 2023, Chenopodium album L. and Chenopodium hybridum L. were the predominant weed species, whereas in 2024, C. album and Sorghum halepense [L.] Pers. predominated. Our results showed an increased weed biomass reduction with the addition of an adjuvant to the reduced herbicide rates, especially for the ½× rate of both herbicides. For those treatments, herbicide efficacy was increased by 20%–30% with adjuvant addition. Benefits of adding adjuvants were also noticed at the ¼× dose of both herbicides, although maximum biomass reduction was only up to 45%. The results indicate that lower herbicide rates of mesotrione and foramsulfuron may be sufficiently effective when combined with an adjuvant.
ABSTRACT Sustainable intensification in rice ecologies is critical for food and livelihood security in the Indo‐Gangetic Plains (IGP) of South Asia. Conventional tillage (CT) in the rice–wheat (R–W) system often degrades soil health, increases weed infestation and reduces resource‐use efficiency. Reduced tillage (RT) with added crop residues offers potential to address these challenges. Weed seedbanks are the primary source of recurrent weed infestation in cereal‐based production, yet their dynamics under CA remain poorly documented. This study hypothesized that RT and added residues in diversified cropping would suppress weed seedbank density, alter weed diversity and enhance crop productivity compared to CT and residue removal. A 10‐year field experiment (2012–2022) was conducted in a factorial randomized block design with CT, RT and RT with 30% residue retention (RTR30) under three rotations of R–W, rice–maize (R–M) and rice–chickpea (R–C). Weed seedbank density and diversity were assessed using the seedling emergence method. After 10 years, viable weed seed density varied for CT and RT under crop rotations. In the 0–10 cm layer, RTR30 lowered Echinochloa colona (L.) Link by 65.9% in R–M but increased Leptochloa chinensis (L.) Nees by 48.4% in R–C. Trianthema portulacastrum L. increased by 40.8% under RT in R–M but declined by 52.7% with RTR30 in R–W. In the 10–20 cm layer, densities were generally lower, with T. portulacastrum declining by 83.4% under RT in R–C, while E. colona increased by 27.6% under RTR30 in R–W. Within CT, R–C exhibited 2.1%–9.2% higher weed diversity than R–W and R–M. Under RTR30 in surface soil, weed diversity declined in R–C, with the Shannon index 29.2% lower than in R–W. For system productivity, RTR30 in R–M maintained higher productivity (11.3 Mg ha −1 ), with 11.9% and 21.6% greater than R–W (10.1 Mg ha −1 ) and R–C (9.29 Mg ha −1 ). These results demonstrate that combining RT with residue retention and diversified rotations, particularly R–M and R–C, can suppress the weed seedbank, simplify weed community structure and improve productivity. This approach offers a scalable strategy for sustainable production of IGP, reducing weed pressure while enhancing yield and system resilience. Findings provide critical insights for designing integrated weed management and cropping strategies adaptable across South Asian rice ecologies.
