Russian thistle (Salsola tragus L.) is a significant summer annual weed in the semi-arid Pacific Northwest (PNW), causing yield losses of up to 50%. Understanding the biology and ecology of S. tragus is vital for developing effective integrated weed management (IWM) strategies. This study focused on 1) S. tragus emergence and seedbank persistence in two cropping systems: fallow–winter wheat (Triticum aestivum L.) and spring wheat–fallow–winter wheat rotations, and 2) S. tragus plant biomass and viable seed production in fallow and spring wheat fields. A four-year experiment (2020-2023) was conducted at the Columbia Basin Agriculture Research Center (CBARC) in Adams, OR, using a randomized block design with four replications. Salsola tragus seeds were sprinkled only at the beginning of the experiment, and seedling numbers were recorded throughout. Most seedlings emerged in the first year, with the highest rates in spring wheat (72%) and fallow (32%), followed by significantly lower rates (0.25-5%) in subsequent years. Seedling emergence began in late March and early April for the first two years but was delayed to May for the third year. Plant biomass and viable seed production were greater in fallow than in spring wheat, with early-season plants having more biomass than later-emerging plants. Plants emerged between early and mid-May produced the most viable seeds. Viable seed production was very low until it peaked in mid-September. Findings indicated that most S. tragus seedlings emerged in the first year after dispersal coinciding with spring precipitation and lasting approximately two months. Additionally, most S. tragus plants produce viable seeds in September, and seeds persist in the soil for more than two years. These results demonstrate the need for growers to control S. tragus emergence to prevent reinfestations and ultimately the need to control S. tragus plants before September to prevent the species from producing viable seed.

This article reviews the first textbooks focused on weed identification published in the United States. We go on to discuss those species considered the most troublesome weeds in agriculture. Common and scientific names written in the original texts have been cross referenced to current common and scientific names.

Developing an effective weed management strategy is crucial to sustainable rice production in Nigeria. Rainfed lowland ecology contributes significantly to the volume of rice cultivated in terms of yield and land acreage. Nevertheless, increased weed infestation remains one of the major production constraints. This review highlights the strength and weaknesses of weed management practices in rainfed lowland ecology and research gaps, and examines the potential for developing a sustainable weed management strategy for lowland rice. In this review, a rainfed lowland situation is described (where water is limited) to engage flooding as a potential weed control option, due to the undulating land terrains. Effective weed management begins with creating a weed-free environment at the critical crop growth stages, such that broadcasted or transplanted rice seedlings can efficiently use water, nutrients, and light. Sustainable weed management practices in Nigerian lowland ecology would therefore imply that farmers begin to incorporate crop rotation to suppress problem weeds in continuous rice cropping systems; adopt conventional or minimum tillage to enhance herbicide efficacy and early establishment of rice; adopt weed-competitive and high-yielding cultivars; and practice appropriate spacing, seeding rate, and seeding methods that can support easy adoption of mechanical weeders and optimum plant population to suppress weed pressure at a later growth stage. This is feasible where farmers are supported with infrastructure, farm machinery, and other necessary inputs. Future research should engage lowland rice farmers in specific agroecological zones.

A 3-yr field study was conducted in Keiser, AR, to investigate the response of the naturally occurring weed flora, dominated by Palmer amaranth, under various combinations of 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide-based programs and crop rotation sequences. In the first year, corn plots were established with three corn HPPD-based herbicide programs designed to represent a range of efficacies and selection pressures for resistance. In the following two years, corn as monoculture or with soybean and/or cotton crops was included in the rotation sequence for selected herbicide programs. Weed emergence, weed biomass, and soil seedbank were assessed through the entire experimental period. The results show that crop rotation, especially a rotation sequence with corn followed by (fb) soybean fb cotton, and the lowest-risk herbicide program involving seven sites of action over the course of the entire crop rotation was effective in reducing the emergence of naturally occurring weeds, including Palmer amaranth, prickly sida, morningglory species, and grass weeds (broadleaf signalgrass, large crabgrass, barnyardgrass, and johnsongrass) by 88.3%, 57.5%, 28.7%, and 76.3%, respectively. Treatments without crop rotation (corn as monoculture for 3 consecutive years) and poor herbicide programs, with one site of action, increased weed emergence, notably of Palmer amaranth and prickly sida, by 73.5% and 74.1%, respectively. The soil seedbank showed a similar trend to weed emergence. This study highlights the fact that reducing the weed seedbank cannot rely on one management practice but requires a multitactic approach with various control methods. HPPD-inhibiting herbicide programs seem to be effective on Palmer amaranth when coupled with crop rotation and should be used with other best management practices.

Seed retention, and ultimately seed shatter, are extremely important for the efficacy of harvest weed seed control (HWSC) and are likely influenced by various agroecological and environmental factors. Field studies investigated seed-shattering phenology of 22 weed species across three soybean [Glycine max (L.) Merr.]-producing regions in the United States. We further evaluated the potential drivers of seed shatter in terms of weather conditions, growing degree days, and plant biomass. Based on the results, weather conditions had no consistent impact on weed seed shatter. However, there was a positive correlation between individual weed plant biomass and delayed weed seed–shattering rates during harvest. This work demonstrates that HWSC can potentially reduce weed seedbank inputs of plants that have escaped early-season management practices and retained seed through harvest. However, smaller individuals of plants within the same population that shatter seed before harvest pose a risk of escaping early-season management and HWSC.

Wild mustard (Sinapis arvensis L.) is a widespread weed of the southeastern cropping region of Australia. Seed germination ecology of S. arvensis populations selected from different climatic regions may differ due to adaptative traits. Experiments were conducted to evaluate the effects of temperature, light, radiant heat, soil moisture, salt concentration, and burial depth on seed germination and seedling emergence of two populations (Queensland [Qld] population: tropical region; and Victoria [Vic] population: temperate region) of S. arvensis. Both populations germinated over a wide range of day/night (12-h/12-h) temperatures (15/5 to 35/25 C), and had the highest germination at 30/20 C. Under complete darkness, the Qld population (61%) had higher germination than the Vic population (21%); however, under the light/dark regime, both populations had similar germination (78% to 86%). At 100 C pretreatment for 5 min, the Qld population (44%) had higher germination than the Vic population (13%). Germination of both populations was nil when given pretreatment at 150 and 200 C. The Vic population was found tolerant to high osmotic and salt stress compared with the Qld population. At an osmotic potential of −0.4 MPa, germination of Qld and Vic populations was reduced by 85% and 42%, respectively, compared with their respective controls. At 40, 80, and 160 mM sodium chloride, germination was lower for the Qld population than the Vic population. Averaged over the populations, seedling emergence was highest (52%) from a burial depth of 1 cm and was nil from 8-cm depth. Differential germination behaviors of both populations to temperature, light, radiant heat, water stress, and salt stress suggest that populations of S. arvensis may have undergone differential adaptation. Knowledge gained from this study will assist in developing suitable control measures for this weed species to reduce the soil seedbank.

Navua sedge [Cyperus aromaticus (Ridley) Mattf. & Kük.] is an aggressive perennial sedge native to equatorial Africa that has become problematic in many Pacific islands and wet, tropical Queensland, Australia. It has had a significant impact on the livestock-grazing industry, sugarcane (Saccharum officinarum L.) and banana (Musa acuminata Colla) plantations, and various other ecosystems. A laboratory-based research investigation was conducted to understand germination and emergence requirements under various environmental conditions of three geographically varied populations sourced from South Johnstone (SJ), Mackay (M) and Nyleta Creek (NC) in Queensland. Germination was identified to be stimulated by light, with no germination recorded under darkness. Populations SJ and NC had optimal germination at alternating temperatures of 25/15, 30/20, and 35/25 C, whereas population M had optimal germination at 25/15 and 30/20 C. All populations recorded greater than 85% germination at all pH levels tested. Seeds of population SJ were more sensitive to salinity compared with populations M and NC, with SJ showing no germination at 100 mM, whereas populations M and NC had 23% and 9% germination, respectively. An inverse relationship was observed between osmotic potential and germination, with no germination recorded at osmotic potentials below −0.8 MPa in any population, indicating moisture availability is a critical requirement for germination. Exposing seeds to 120 C radiant heat completely inhibited germination in populations M and NC, whereas 3% of population SJ germinated following a 180-s exposure at 120 C. Seedling emergence decreased as planting depth increased. Emergence was greatest for seeds on the soil surface or at 0.5-cm burial depth, consistent with germination being stimulated by light. Knowledge of these biological characteristics of C. aromaticus seed germination will assist in investigation of suitable control actions for this species, particularly in the early stage of its invasion into new areas, and will contribute to significant reduction in the soil seedbank.

Hairy fleabane [Conyza bonariensis (L.) Cronquist] is a problematic weed in Australian no-till cropping systems. Consequently, a study was conducted to examine the effect of temperature, light, salt stress, osmotic stress, burial depth, and sorghum crop residue on germination and emergence in two populations (C and W: collected from chick pea [Cicer arietinum L.] and wheat [Triticum aestivum L.] fields, respectively) of C. bonariensis. Both populations were able to germinate over a wide range of alternating day/night temperatures (15/5 to 35/25 C); however, the C population had optimum (and similar) germination over the range of 20/10 and 30/20 C, while the W population showed maximum germination at 25/15 C. A negative relationship was observed between osmotic potential and germination, with 31% and 14% germination of the C and W populations at −0.6 MPa, respectively. These observations suggest that population C was more tolerant to higher osmotic potentials than population W. Seeds of both populations germinated when exposed to a wide range of sodium chloride levels (NaCl, 0 to 200 mM); however, beyond 200 mM NaCl, no germination was observed in either population. Maximum germination of the C (70%) and W (41%) populations was observed on the soil surface with no emergence from a burial depth of 1 cm. The application of sorghum residue at an amount of 6,000 kg ha−1 reduced emergence of the C and W populations by 55% and 58%, respectively, compared with the no-residue treatment. Knowledge gained from this study suggests that the following strategies could be used for more efficacious management of C. bonariensis: (1) a shallow-tillage operation to bury weed seeds in conventional tillage systems, and (2) retention of sorghum residue on the soil surface in no-till systems.

Greenhouse experiments were conducted in 2016 at Pontotoc and Verona, MS. On March 3 (Pontotoc) and March 7 (Verona), landscape fabric was placed in the bottom of polyethylene lugs, each 0.22 m2, then approximately 5 cm of a 1:1 (v/v) blend of soilless potting media and masonry sand was added. ‘Beauregard’ sweetpotato [Ipomoea batatas (L). Lam.] storage roots weighing between 85 and 227 g, and several with emerging sprouts ≤1 cm, were placed longitudinally in a single layer on the substrate, then covered with an additional 3 cm of the substrate. Sprouted yellow nutsedge (Cyperus esculentus L.) tubers were transplanted equidistantly into sweetpotato-containing lugs at six densities: 0, 18, 36, 73, 109, and 145 m−2. Trials were terminated 55 and 60 d after planting at Pontotoc and Verona, respectively. Predicted total sweetpotato stem cuttings (slips) decreased linearly from 399 to 312 m−2 as C. esculentus density increased from 0 to 145 m−2. Predicted total slip dry weight at a C. esculentus density of 145 m−2 was reduced 21% compared with 0 m−2. Predicted rotten sweetpotato storage roots increased from 2.6 to 11.3 m−2 as C. esculentus density increased from 0 to 145 m−2. In response to increasing C. esculentus density, sweetpotato seed roots exhibited increased proximal-end dominance.

Continuous use of heavy machinery in fields and frequent farm traffic sometimes result in soil compaction. Soil compaction reduces the oxygen (O2) concentration in soil capillaries and hence lowers the O2 availability for germinating seeds. We investigated how reduced O2 levels changed germination behavior of weeds to elucidate their potential to adapt to O2-deficient soils (compacted, compressed, and waterlogged soils and soils with hard surfaces). Two similar laboratory experiments were conducted with five O2 treatments (20.9%, 15%, 10%, 5%, and 2.5%). The germination percentage of the invasive weed hairy fiddleneck [Amsinckia menziesii (Lehm.) A. Nelson & J.F. Macbr. var. menziesii] and the common weeds common lambsquarters (Chenopodium album L.) and Persian speedwell (Veronica persica Poir) was not significantly reduced at 15% O2. The germination of scarlet pimpernel (Anagallis arvensis L. ssp. arvensis), silky windgrass [Apera spica-venti (L.) Beauv.], catchweed bedstraw (Galium aparine L.), and knawel (Scleranthus annuus L.) was significantly reduced at 15% O2. The highest germination was obtained at 20.9% O2 for blackgrass (Alopecurus myosuroides Huds.), A. spica-venti, G. aparine, annual bluegrass (Poa annua L.), wild mustard (Sinapis arvensis L.), scentless chamomile [Tripleurospermum inodorum (L.) Sch. Bip.], field violet (Viola arvensis Murray) and the less common weeds A. arvensis and S. annuus. Distribution of flora in the landscape may change on O2-deficient soils by reducing germination of some species such as A. arvensis and S. annuus and favoring others like A. menziesii and C. album. The ability to germinate at 2.5% and 5% O2 may contribute to explain why A. myosuroides and A. menziesii have become successful as weeds on O2-deficient soils, as they maintained a germination percentage between 34% and 58% at 2.5% O2.

Effective integrated weed management in agricultural landscapes depends on the ability to identify and manage processes that drive weed dynamics. The current study reports the effects of grazing management and crop rotation strategies on the seedbank and emerged weed flora in an integrated crop-livestock system (ICLS) experiment during a 12-year period under no-tillage in sub-tropical southern Brazil. During winter, Italian ryegrass cover crops were grazed by sheep: grazing management treatments included two stocking methods (continuous and rotational) and two forage allowances (10 and 20 kg of herbage dry matter available per 100 kg animal live weight). During summer, the crop rotation treatments involved either soybean-maize or soybean-soybean in succession with winter-grazed cover crops. The treatments were part of a factorial randomized complete block design. Treatment effects were evaluated on the weed seedbank and emerged weed flora populations during winter-grazed cover crop and summer crop growth as well as during the harvest phase. The current results demonstrate that crop rotation and grazing management exhibited interactive effects on the determination of weed outcomes in an ICLS. However, overall, compared with moderate forage allowance, high forage allowance during the winter-grazed cover crop caused lower emerged weed flora in subsequent crops (20% reduction during crop growth and 90% reduction at crop harvest) and 48% reduction in seedbank size. High forage allowance promoted more residue from winter-grazed cover crop biomass, which remained during the summer crop phases and probably resulted in a physical barrier to weed emergence.

African turnipweed (Sisymbrium thellungii O. E.Schulz) is an emerging problematic broadleaf weed of the northern grain region of Australia. Laboratory experiments were conducted to evaluate the effects of temperature, light, salinity, pH, seed burial depth, and the amount of wheat crop residue on germination and emergence of two Australian S. thellungii weed populations (population C, cropped area; population F, fence line). Both populations behaved similarly across different environmental conditions, except in the residue study. Although the seeds of both populations of S. thellungii could germinate under complete darkness, germination was best (~95%) under light/dark conditions at the 20/10 C temperature regime. Both populations of S. thellungii germinated over a wide range of day/night temperatures (15/5, 20/10, 25/15, and 30/20 C). Osmotic stress had negative effects on germination, with 54% seeds (averaged over populations) able to germinate at −0.1MPa. Complete germination inhibition for both populations was observed at −0.8MPa osmotic potential. Both populations germinated at sodium chloride (NaCl) concentrations ranging from 50 to 100 mM, beyond which germination was completely inhibited. There were substantial reductions in seed germination, 32% (averaged over populations) under highly acidic conditions (pH 4.0) as compared with the control (water: pH 6.4). Seed germination of both populations on the soil surface was 77%, and no seedlings emerged from a burial depth of 1 cm. The addition of 6 Mg ha−1 of wheat (Triticum aestivum L.) residue reduced the emergence of the C and F populations of S. thellungii by 75% and 64%, respectively, as compared with the control (no residue). Information gathered from this study provides a better understanding of the factors favorable for germination and emergence of S. thellungii, which will aid in developing management strategies in winter crops, especially wheat, barley (Hordeum vulgare L.), and chick pea (Cicer arietinum L.).

Accurate weed emergence models are valuable tools for scheduling planting, cultivation, and herbicide applications. Multiple models predicting giant ragweed emergence have been developed, but none have been validated in diverse crop rotation and tillage systems, which have the potential to influence weed emergence patterns. This study evaluated the performance of published giant ragweed emergence models across various crop rotations and spring tillage dates in southern Minnesota. Across experiments, the most robust model was a mixed-effects Weibull (flexible sigmoidal function) model predicting emergence in relation to hydrothermal time accumulation with a base temperature of 4.4 C, a base soil matric potential of −2.5 MPa, and two random effects determined by overwinter growing degree days (GDD) (10 C) and precipitation accumulated during seedling recruitment. The deviations in emergence between individual plots and the fixed-effects model were distinguished by the positive association between the lower horizontal asymptote (Drop) and maximum daily soil temperature during seedling recruitment. This finding indicates that crops and management practices that increase soil temperature will have a shorter lag phase at the start of giant ragweed emergence compared with practices promoting cool soil temperatures. Thus, crops with early-season crop canopies such as perennial crops and crops planted in early spring and in narrow rows will likely have a slower progression of giant ragweed emergence. This research provides a valuable assessment of published giant ragweed emergence models and illustrates that accurate emergence models can be used to time field operations and improve giant ragweed control across diverse cropping systems.

Harvest weed seed control is an alternative non-chemical approach to weed management that targets escaped weed seeds at the time of crop harvest. Relatively little is known on how these methods will work on species in the US. Two of the most prominent weeds in soybean production in the midsouthern US are Palmer amaranth and barnyardgrass. Typically, when crop harvesting occurs the weed seed has already either shattered or is taken into the combine and may be redistributed in the soil seedbank. This causes further weed seed spread and may contribute to the addition of resistant seeds in the seedbank. There is little research on how much seed is retained on different weed species at or beyond harvest time. Thus, the objective of this study was to determine the percentage of total Palmer amaranth and barnyardgrass seed production that was retained on the plant during delayed soybean harvest. Retained seed over time was similar between 2015 and 2016, but was significantly different between years for only Palmer amaranth. Seed retention did not differ between years for either weed species. Palmer amaranth and barnyardgrass retained 98 and 41% of their seed at soybean maturity and 95 and 32% of their seed one month after soybean maturity, respectively. Thus, this research indicates that if there are escaped Palmer amaranth plants and soybean is harvested in a timely manner, most seed will enter the combine and offer potential for capture or destruction of these seeds using harvest weed seed control tactics. While there would be some benefit to using HWSC for barnyardgrass, the utility of this practice on mitigating herbicide resistance would be less pronounced than that of Palmer amaranth because of the reduced seed retention or early seed shatter.

This study uses two novel archaeobotanical techniques – crop carbon and nitrogen isotope analysis and functional weed ecology – to determine directly how the intensity of agricultural practice changed from the Neolithic to the Early Iron Age in south-west Germany, with the emergence of fortified hilltop settlements (Fürstensitze or chiefly seats) regarded as the first urban centres in central Europe. The crop isotope and functional weed ecological evidence suggest that surplus cereal production in the Early Iron Age was achieved through sustained use of manure combined with expansion in arable cultivation, both developments that are connected with more widespread use of animal traction. The increased scale of cultivation is broadly apparent across rural as well as fortified hilltop centres in the Early Iron Age, and considerable variability in manuring intensity is consistent with agricultural decision-making at a local level rather than centralised control. Additionally, the more intensive manuring of hulled six-row barley, used in beer production, demonstrates that the political importance of drinking and feasting in Early Iron Age society was reflected in crop husbandry practices. In terms of animal husbandry, faunal isotope data reveal a radical decrease in forest cover, potentially reflecting an expansion in the scale of herding accompanying that of arable cultivation. Site-specific patterning points to a range of herding strategies, from specialised herding of cattle at the Heuneburg to generalised patterns of livestock management at rural sites.

The effect of tillage systems on depth of emergence and densities of giant and green foxtail under different environmental and cropping conditions were evaluated from 1985 to 1987 at Arlington, Hancock, and Janesville, WI. Mean emergence depths in no-till were the shallowest, followed by chisel plow and conventional tillage at each location. At least 40% of the giant and green foxtail plants emerged from the upper 1 cm of soil in no-till compared to about 25% in chisel plow and less than 15% in conventional tillage. As many as 25% of the plants emerged from greater than 4 cm in conventional tillage compared to about 10% in chisel plow and less than 5% in no-till. Seedlings emerged from greater depths in a loamy sand than in a silt loam soil regardless of tillage system. At Arlington, green foxtail was the dominant species in conventional tillage, while giant foxtail dominated in chisel plow and no-till. Foxtail densities were greater in chisel plow and no-till than in conventional tillage at all three locations.

The species composition and density of weed seed in the soil vary greatly and are closely linked to the cropping history of the land. Altering tillage practices changes weed seed depth in the soil, which plays a role in weed species shifts and affects efficacy of control practices. Crop rotation and weed control practices also affect the weed seedbank. Information on the influence of cropping practices on the weed seedbank should be a useful tool for integrated weed management. Decision aid models use information on the weed seedbank to estimate weed populations, crop yield loss, and recommend weed control tactics. Understanding the light requirements of weed seed may provide new approaches to weed management. Improving and applying our understanding of weed seedbank dynamics is essential to developing improved weed management systems. The principles of plant ecology must be integrated with the science of weed management to develop strategies that take advantage of basic plant responses in weed management systems for agronomic crops.

Survival and growth of five collections of big sagebrush were compared in reciprocal transplant gardens. The study was designed to further the understanding of seedling ecology of this important rangeland plant. Survival of transplanted seedlings was not tied to their origin, but antagonism for collection site in survival was apparent for some collections. The site with the highest environmental potential as indexed by native plant community, soil development, and precipitation had the poorest seedling survival. The site with the lowest environmental potential produced seedlings that had the highest survival across all reciprocal gardens. The average mortality level after 3 yr was 11%, indicating that seedlings of big sagebrush can be transplanted successfully. In dry years, the collection from the driest location had the highest amount of juvenile biomass accumulation. However, during a season with much above-normal precipitation this was reversed and the amount of growth for this source was below levels observed for the dry years. The relation between subspecies of big sagebrush and survival or growth of the collections used in this study was not clear. Because collections were made on arid extremes of the subspecies they may reflect introgressive populations among subspecies.

Yellow and purple nutsedge and southern root-knot nematode are common pests in intensively managed chile pepper production. Greenhouse studies were conducted to identify relationships among nutsedge species, chile peppers, and root-knot nematode. All practical combinations of the plant species and nematodes were grown together in pots for 14 wk. Both nutsedges and root-knot nematode reduced chile pepper height over time with no interaction. Competition from purple nutsedge or either nutsedge species plus nematodes reduced chile pepper top weight more than yellow nutsedge or nematodes alone. All pest combinations reduced chile pepper root weight. Chile pepper and nematodes individually reduced rates of shoot production, as well as top and belowground weights of yellow and purple nutsedge. Chile pepper and purple and yellow nutsedge hosted root-knot nematode host race 3. Nematode egg production was greater on chile pepper roots than on either nutsedge species. Purple nutsedge growing with chile pepper increased nematode production g−1 of chile pepper root. Purple nutsedge grown with chile pepper was the most detrimental for chile pepper growth, but most efficient for maintaining the root-knot nematode population on the least amount of root biomass. Since root-knot nematode infests yellow and purple nutsedge, and few nematicides are available for nematode control, root-knot nematode cannot be managed with crop rotation if nutsedge is not controlled.