SummaryMikania micrantha (mile‐a‐minute) reproduces both by seed and vegetatively. A study to determine the possible pollinators, seed production rates, temperature and salinity limitations to germination and its seedbank size and persistence was conducted in Viti Levu, Fiji. Representatives of the Diptera had the greatest percentage of all floral visits (38%), followed by Hymenoptera (34%) and Lepidoptera (27%), while the honeybee was the most recurring visitor (18% of all visits). Flower heads (capitula) within the inflorescence commonly formed four viable seeds, resulting in 60 820 filled seed being produced per m2. However, the seedbanks formed were not massive (600 seed m−2) and they were moderately persistent (T50: 1–3 years). Seed germination from both high and moderate rainfall regions occurred rapidly, under a wide range of temperature regimes, with no primary dormancy being observed. This study indicates that the seed reproductive success of M. micrantha in the two rainfall regions of Fiji is due to a number of factors, including the production of large numbers of flowers, successful pollination by local insects and the subsequent production of a large number of viable seeds. These seeds have high viability, no dormancy and are capable of forming small‐to‐medium seedbanks that are moderately long‐lived. In addition, seeds can germinate under a wide range of temperature and salinity conditions. This knowledge on seed production, biology, longevity and salt tolerance is vital in the development of management plans of M. micrantha in Fiji.

SummaryThis study describes the seedbank persistence of glyphosate‐resistant (GR) Kochia scoparia at two sites in western Canada and examines if GRK. scoparia from western Canada and mid‐western United States (USA) differ from their susceptible counterparts in seed germination and early growth characteristics at low‐temperature regimes. Site or depth of seed burial (surface, 2.5 cm, 10 cm) did not affect seed viability over time and time to 50% and 90% loss of viability averaged 210 and 232 days respectively. Glyphosate‐resistant K. scoparia generally germinated later and had lower cumulative germination than glyphosate‐susceptible (GS) K. scoparia from Saskatchewan, Canada; and Kansas, USA; but not Colorado, USA. Similarly, time to 10% first leaf of GSK. scoparia from Saskatchewan and Kansas tended to be sooner than that of GRK. scoparia, with a greater percentage of GS vs. GR seedlings of populations from all regions having attained first leaf by the end of the experiment. The short seedbank longevity and delayed and reduced germination and time to first leaf of GRK. scoparia may potentially be exploited to maximise management efficacy through delayed preseeding weed control or alternatively by early seeding date to enhance crop competitiveness.

SummaryEcological niche models are widely used in the study of weed invasions, yet best approaches for selecting ecologically relevant environmental predictors for weeds remain unresolved. Here, we evaluate niche model transferability based on diverse environmental data sets for an invasive herb, Flaveria bidentis. This species is native to South America, but has established populations in China that pose a threat to agriculture and animal husbandry. Relevant environmental data sets were selected via five statistical approaches: permutation importance (PI) and jackknife test (JK) in Maxent, variable importance identified by boosting regression trees (BRT), ecological niche factor analysis (ENFA) and a newly released algorithm based on a fluctuation index (FI). Climate spaces occupied by native South American and introduced Chinese populations were compared based on these environmental data sets. Native niche model predictions in China were compared across environmental data sets and model settings (i.e. default versus fine‐tuned Maxent settings). Results suggest that native and introduced populations occupy two distinct climate spaces, but that this divergence likely results from background effects. Niche models based on fine‐tuned Maxent settings generally showed better discrimination ability than those based on default settings. The best model discrimination in China was attained in the FI model using fine‐tuned settings, followed by the BRT model on default settings. The best models suggest that highly suitable areas at risk of invasion in China are to the west and north‐east of present distributional areas. Results presented here provide predictions for F. bidentis in particular, but also shed light on procedures for selecting ecologically relevant predictors for invasive species distributional predictions more generally.

SummaryThe genus Echinochloa (Poaceae) includes numerous problematic weeds over a wide range of ecoregions in the world. To date, molecular markers for species identification and assessing phylogenetic relationship are still limited in the genus Echinochloa. In this study, we developed seven chloroplast molecular markers based on divergent chloroplast regions of E. crus‐galli and E. oryzicola. Furthermore, Marker #1 (psbA) was examined in more than 200 Echinochloa accessions and a phylogenetic tree grouped these Echinochloa accessions into four clades. Additionally, two different E. crus‐galli varieties (E. crus‐galli var. crus‐galli, E. crus‐galli var. praticola) and E. colona were successfully distinguished by this marker. The developed molecular markers contribute to better identification of Echinochloa taxa.

SummaryThe germinability and viability of mature seeds of five grass (Hordeum spp., Bromus diandrus, Vulpia spp., Avena fatua and Lolium rigidum) and seven broad‐leaved weed species (Echium spp., Physalis hederifolia, Solanum elaeagnifolium, Raphanus raphanistrum, Marrubium vulgare and Malva parviflora) that were either untreated, ensiled for a minimum of three months, underwent 48 h in sacco digestion in steers or ensiled prior to digestion were tested for germinability and viability. Ensiling and digestion both reduced seed viability, although the extent varied with species. The effect of ensiling was generally greater compared with digestion and differed between years for some species. Ensiling or ensiling plus digestion rendered all seeds of Hordeum spp., B. diandrus, Vulpia spp., A. fatua, Echium spp., P. hederifolia (in one year only), S. elaeagnifolium, R. raphanistrum and M. vulgare non‐viable; ensiling and ensiling plus digestion reduced viability of L. rigidum by 74.4% and 92.7% respectively. Viability of M. parviflora displayed the greatest tolerance to damage, with seed viability reduced on average by 31.4%, 27.6% and 27.4% for ensiling, digestion and ensiling plus digestion treatments respectively. These results indicate that ensiling can provide an effective non‐chemical weed management option, as a component of an integrated weed management package, for certain weed species responsible for significant crop and pasture production losses in Australian and world temperate and Mediterranean agricultural systems.

Non-chemical weed management covers all management practices that influence weeds except herbicides. This chapter summarises the major achievements in European research, as well as work undertaken in North America. Research groups from both continents have interacted strongly on the topic over the years and shared common interests on the development of non-chemical tactics. The chapter encompasses preventive, cultural and direct weed control methods, explaining the basic principles and the integration of these tactics in weed management strategies for agricultural and horticultural crops and in some cases amenity areas as well. Preventive methods reduce weed germination, cultural methods improve crop competition and direct physical weed control reduces weed survival. Non-chemical weed management is mainly adopted in organic crop production, as conventional growers still perceive it as more costly and less reliable than herbicide-based weed control programmes.

Weeds must be considered in any conceptual framework that seeks to explain, explore and analyse biodiversity if the focus is on human activities and utilisation of natural systems. This chapter concentrates on weeds in annual and perennial crops associated with terrestrial systems used for agricultural purposes: weeds of non-terrestrial or nonagricultural sites are not considered. Genetic diversity within weed species; weed species diversity in the context of conservation; and the particular role of weeds and their seeds for food webs are discussed. The size of seed-based food webs in agroecosystems is largely determined by the amount of energy produced by weed seeds. The chapter describes how aspects of weed biodiversity, besides the conservation of rare species, can be used to induce, guide or evaluate sustainable development in arable production. The local weed species diversity is shaped by both site conditions and arable management adapted to those conditions.

SummaryVolunteer summer‐annual oilseed rape (sOSR; Brassica napus) is an ongoing concern in Canadian crop production. Large harvest seed losses and secondary dormancy in this species generate a persistent volunteer seedbank. Yield loss in subsequent crops, potential sOSR oil profile contamination and herbicide‐resistance trait introgression create a need for effective sOSR seedbank management. This field study evaluated the effects of timing and type of implement of post‐harvest soil disturbance and seeding a winter cereal on volunteer sOSR population persistence and demographic life‐stage transition rates at five locations in Manitoba, Canada. Following sOSR harvest and supplemental seed rain, seedbank densities ranged from 6770 to 15360 and 50 to 2610 seeds m−2 among sites in autumn and spring respectively. In contrast to European research on winter‐annual oilseed rape, early autumn soil disturbance, shortly after sOSR harvest, was the best strategy to decrease volunteer sOSR persistence (3% population persistence from autumn to spring, compared with 6% in zero tillage). Substantial autumn seedling recruitment (38% of the autumn seedbank) and subsequent winterkill contributed to lower population persistence. Soil disturbance in spring stimulated spring seedling recruitment compared with other disturbance timings (11% and 3% of the spring seedbank, respectively). The implement used for soil disturbance and seeding winter wheat (Triticum aestivum) had minimal effect on population persistence. This research showed that timing of post‐harvest soil disturbance should be utilised as an effective tactic to decrease population persistence of volunteer sOSR via stimulation of autumn seedling recruitment and concomitant winterkill.

SummaryGlyphosate‐resistant Ambrosia trifida is a competitive and difficult‐to‐control annual broad‐leaved weed in several agronomic crops in the Midwestern United States and Ontario, Canada. The objectives of this study were to compare treatments for control of glyphosate‐resistant A. trifida with tillage followed by pre‐emergence (PRE) and/or post‐emergence (POST) herbicides in glyphosate‐resistant maize and to determine the impact of A. trifida escapes on maize yield. Field experiments were conducted in 2013 and 2014 in grower fields infested with glyphosate‐resistant A. trifida. Tillage prior to maize sowing resulted in 80–85% control compared with no tillage. Tillage followed by PRE application of saflufenacil plus dimethenamid‐P with or without atrazine resulted in 99% control compared with ≤86 and 96% control with PRE herbicides alone at 7 and 21 days after application respectively. Tillage or POST‐only herbicides resulted in 4–14 A. trifida plants m−2, whereas a PRE and POST programme had <3 plants m−2. Maize yield was greatest (13.1–14.2 tonnes ha−1) with tillage followed by PRE and POST herbicide programme. The relationship between maize yield and late‐season density of A. trifida escapes showed a 50% maize yield reduction irrespective of control measures when A. trifida density was 8.4 plants m−2. It was concluded that the combination of tillage with PRE and/or POST herbicides reduced A. trifida density and biomass accumulation early in the season and provided an integrated approach for effective management.