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Copyright of Revista de Ciências Agrárias is the property of Sociedade de Ciencias Agrarias de Portugal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Large crabgrass (Digitaria sanguinalis) is one of the most problematic weeds in summer crops in Argentina. Emergence throughout the season of several cohorts allows the weed to escape postemergence control. Demographic models are useful tools to understand and compare the effect of different agronomic management decisions on weed population growth, as well as to identify critical functional stages that affect population growth rates. The objectives of this work were (i) to study population dynamics of D. sanguinalis in soybean, (ii) to determine the effect of glyphosate application timing on weed demographic parameters and soybean yield losses, and (iii) to evaluate the effect of weed density on soybean yield loss. A field experiment was conducted in two locations, in a completely randomized design with three replicates. Treatments included a control without glyphosate and glyphosate applied at soybean stages V4 or R1. The demographic stages (initial seedbank, seedlings, and adult plants) and parameters (establishment, survival, and fecundity) were estimated. Reproductive organs were evaluated in each cohort, including raceme per plant, spikelets per raceme, and seeds per spikelet. Weed and crop biomass and yield crop were assessed at harvest. Three cohorts were identified, the first of which emerged in November and contributed 93% of the total seedlings and 71% of the total adults. Glyphosate applied at V4 reduced the survival rate of the first cohort, as well as the total shoot biomass and the fecundity rate, increasing the biomass and crop grain yield. Both application timings affected tillers per plant, racemes per tiller, and fertile spikelets per raceme. Glyphosate at R1 did not effectively reduce weed competition, but reduced seed production as application at V4. Yield losses estimated with the model of the rectangular hyperbola according to weed density showed a yield loss at low densities (I) of 18%, and a maximum yield loss (A) of 82%. To avoid yield losses, herbicide applications targeting the first cohort are more effective than later applications targeting subsequent cohorts. However, at both times glyphosate applications reduced the number of seeds entering the seedbank, and therefore the population growth rate. [ABSTRACT FROM AUTHOR]

Weeds are a major problem in cutting propagation and compete with the main crop for water, sunlight, and nutrients, thus reducing growth and marketable quality of rooted cuttings. Due to the high labor cost of hand weeding, mulches can be an alternative method for weed control in the propagation environment. The objective of this research was to determine the effect of mulches (coarse vermiculite, rice hulls, paper pellets, and pine pellets) on rooting of stem cuttings and weed control when applied at 0.5- and 1-inch depths. Cuttings of three plant species [‘Nanho Blue’ butterfly bush (Buddleja davidii), ‘Catawba’ crape myrtle (Lagerstroemia indica), ‘Phantom’ hydrangea (Hydrangea paniculata)] were stuck in 2.5-inch-diameter containers filled with pine bark substrate and treated with mulch. In a separate study, seeds of four weed species [creeping woodsorrel (Oxalis corniculata), hairy bittercress (Cardamine hirsuta), large crabgrass (Digitaria sanguinalis), mulberry weed (Fatoua villosa)] were sown onto the mulch surface. Rooting percentage was unaffected by mulch type or depth for any of the three crop species (‘Nanho Blue’ butterfly bush, ‘Catawba’ crape myrtle, ‘Phantom’ hydrangea). Pine pellets did not affect root dry weight of any crop species, but root length and volume of ‘Catawba’ crape myrtle was reduced by pine pellets at 1-inch depth. Rice hulls slightly reduced the root length and volume of ‘Catawba’ crape myrtle, but the reduction was less than 50%. Pine pellets and paper pellets (both depths) reduced growth of all four weed species. Even though weed seeds germinated in pine and paper pellets, seedlings did not grow large enough to potentially affect crop rooting. In conclusion, pine pellets and paper pellets at 0.5-inch depth can be effective in suppressing weed populations with minimal effect on rooting.

Context: Different environmental factors occurring during seed development could be responsible for maternal effects on seed dormancy. Understanding these effects on Digitaria sanguinalis (L.) Scop seeds would help to predict it's seedling emergence. Aims: To study D. sanguinalis maternal effects on seed dormancy level under environmental variations imposed by soybean (Glycine max L.) crop, changing (1) nutrient availability, (2) radiation and (3) soybean canopy presence during different phenological stages of the weed. Methods: Field plots experiments under semi-controlled conditions were established to reach these objectives. Key results: Among different factors evaluated, radiation was the most important factor, mainly during the reproductive stages of the weed. The reduction in solar radiation received by the mother plant diminished seed dormancy level even in those panicles receiving full sunlight in shaded plants. Conclusions: Results suggest that solar radiation and temperature operate together in the mother plants to modify seed dormancy level. Implications: Crop management decisions such as long crop cycles, late sowing date and narrow inter-row distances would reduce seed dormancy level and would anticipate a concentrated seedling emergence of the weed. Understanding weed seedling emergence process is very important for researchers and producers to design successful weed management strategies reducing weeds population. In some weeds, seed dormancy is defined during seed development in mother plant, and allows weeds to increase the emerge windows and avoid controls. In our work, we found that the reduction in solar radiation received by the mother plant diminished seed dormancy level which should be considered by producers to establish weed management strategies in the next season. [ABSTRACT FROM AUTHOR]

BACKGROUND: Digitaria sanguinalis has been identified as a species at high risk of evolving herbicide resistance, but thus far, there are no records of resistance to glyphosate. This weed is one of the most common weeds of summer crops in extensive cropping areas in Argentina. It shows an extended period of seedling emergence with several overlapping cohorts during spring and summer, and is commonly controlled with glyphosate. However, a D. sanguinalis population was implicated as a putative glyphosate‐resistant biotype based on poor control at recommended glyphosate doses. RESULTS: The field‐collected D. sanguinalis population (Dgs R) from the Rolling Pampas has evolved glyphosate resistance. Differences in plant survival and shikimate levels after field‐recommended and higher glyphosate doses were evident between Dgs R and the known susceptible (Dgs S) population; the resistance index was 5.1. No evidence of differential glyphosate absorption, translocation, metabolism or basal EPSPS activity was found between Dgs S and Dgs R populations; however, a novel EPSPS Pro‐106‐His point substitution is probably the primary glyphosate resistance‐endowing mechanism. EPSPS in vitro enzymatic activity demonstrated that an 80‐fold higher concentration of glyphosate is required in Dgs R to achieve similar EPSPS activity inhibition to that in the Dgs S population. CONCLUSION: This study reports the first global case of glyphosate resistance in D. sanguinalis. This unlikely yet novel transversion at the second position of the EPSPS 106 codon demonstrates the intensity of glyphosate pressure in selecting unexpected glyphosate resistance alleles if they retain EPSPS functionality. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Digitaria sanguinalis can exhibit a smut caused by Ustilago syntherismae. In the present paper, we deal with the phenotypic expression of the grass that can be observed under field conditions. Plants can be apparently healthy, completely smutted or show both tendencies, inflorescences bearing spikelets and at the same time sori (single individuals). Plasticity in fitness-related traits such as tillering pattern and the proportion of inflorescences with spikelets or completely transformed into sori at individual level was examined in distinctive individuals. In the study period 2011–2014, we observed and collected 244 individual plants (3.2% of the plants reaching the reproductive stage) with between 1 and 12 tillers. The mean number of reproductive structures per plant was 24.2 (20.4 exhibiting sori and 3.7 bearing spikelets). The spatial and temporal dynamics of the single individuals at plot scale was also analysed. We discuss the importance of individual responses from the perspective of plant resistance in the broadest sense: any system that can prevent infection or reduce the impact of fungi. Furthermore, we consider the importance of this subpopulation in disease prevalence. [ABSTRACT FROM AUTHOR]

Summary: Digitaria sanguinalis is a troublesome annual weed that causes important yield losses in different crops. Despite this, there is scarce information about different aspects of its biology under field conditions. New knowledge about the establishment process of this species will be of paramount importance in order to maximise the effectiveness of weed management. The aims of this paper were to evaluate the effect of stubble found on the surface on seed dormancy levels through the season, the effects of stubble and soyabean crop canopy on seedling emergence and to determine the field emergence pattern as a consequence of seed dormancy level at dispersal time. Seeds on the soil surface, which showed a high dormancy level at the beginning of autumn, were released from dormancy by low winter temperatures and germinated during spring as temperatures rose, showing a transient surface seedbank. Seeds covered by stubbles had delayed the emergence in the field due to lower alternating temperatures perceived by the surface seedbank. On the other hand, the presence of a soyabean crop and stubble together reduced the number of seedlings. Seeds with a high dormancy level at dispersal time showed a delayed emergence in the next season when compared with seeds with a lower dormancy level. However, the final number of seedlings was similar. Both stubble on surface and crop canopy are useful factors to lessen and delay the seedling emergence allowing the design of weed management strategies in order to diminish the population levels of this species. [ABSTRACT FROM AUTHOR]

A wild loose smut–summer annual grass interaction was studied to explore the relative importance of some local spatiotemporal patterns of variation for its existence. The prevalence‐related variable measured was the proportion of diseased plants (PDP). The mean annual PDP of nine consecutive seasons (2009–2017) was analysed using a generalized linear model with a binomial distribution considering covariables related to rainfall. During the seasons 2013–2015, the precise location of each sample within the plot was taken into account. The PDP of these seasons was analysed in various ways by means of generalized linear models, searching for its spatial variation with plant density in a given season, and with sorus and seeded inflorescence densities of the previous season. Symptomless plants were estimated as 6.1% of the 2015 population. The mean annual PDP ranged from 0.08 to 0.42 and covaried positively with precipitation. Within the field, two zones could be repeatedly delimited among seasons: one in which high plant densities and high PDP co‐occurred, and another with lower values of both in which PDP depended on the sorus density. The role played by differences in the encounter rate within and among seasons is discussed; lack of encounter could be as necessary as encounter for plant–pathogen coexistence over time. [ABSTRACT FROM AUTHOR]

Large crabgrass is a major grass weed widely distributed across China. This weed infests maize fields and has evolved resistance to the acetolactate synthase (ALS)-inhibiting herbicide nicosulfuron due to continuous and intensive use. In this study, a total of 25 out of 26 large crabgrass populations collected from maize field demonstrated resistance to nicosulfuron. Amino acid modifications in ALS known to confer resistance to ALS-inhibiting herbicides in other weeds, were not found in the 9 tested resistant populations. The P450 inhibitor malathion significantly reversed resistance to nicosulfuron in 3 tested populations, indicating one or more P450s may be involved. Nicosulfuron was metabolized more rapidly in one resistant large crabgrass population than in a susceptible biotype. This demonstrates that the metabolic resistance mechanisms involving one or more P450s may be responsible for large crabgrass resistance to nicosulfuron in this biotype. [ABSTRACT FROM AUTHOR]

Previous research has shown the effectiveness of an ULV (Ultra-Low Volume) sprayer compared to a conventional sprayer for weed control in row crop applications. This sprayer produced comparable disease control and foliar nutrient applications to a conventional sprayer in turfgrass, but has not previously been evaluated for weed control in established turf. Four weed control field studies were conducted in the spring and summer of 2012 and 2013 at the University of Nebraska-Lincoln: John Seaton Anderson Turfgrass Research Facility near Mead, NE, USA to compare the weed control efficacy between a novel ULV sprayer and a conventional sprayer. The studies compared the two sprayers for the control of: ground ivy and dandelion in established turf in a summer application; preemergence control of large crabgrass in established turf in a late spring application and ground ivy control in established turf in a late spring application. No differences were observed in weed control between sprayer types in the four studies over both years of the study despite a thirty fold decrease in application volume rate across different herbicide modes-of-action in all of the studies. The Kamterter ULV sprayer system may be a useful and effective management option for control of the weeds in turfgrass. [ABSTRACT FROM AUTHOR]

Understanding host-pathogen evolutionary dynamics needs characterisation and quantification of processes occurring at many spatiotemporal scales. With this aim, the effects of smut on a naturally infected population of the summer annual Digitaria sanguinalis were followed for 4 years in an uncropped field. The main purpose of the study was to quantify the effects of within-population density on the infectivity and the aggressiveness of the pathogen in a range of densities that occurred naturally. The infectivity-related variable measured was the proportion of smutted plants at the end of each growing season; proportions were analysed using a generalised linear model with a binomial distribution considering the year, the density and their interaction as effects. The aggressiveness-related variables chosen were the number of smutted inflorescences per plant and per area, obtained over the last 2 years; they were analysed by means of ancova considering disease status (seeded or smutted), year, density and all the interactions between them. Although the disease is monocyclic, results showed clearly that infectivity increased with plant density. The number of inflorescences per plant was 1.5 times higher in smutted plants than in healthy plants throughout the range of densities. This variable declined when density increased, but as the infectivity increased at a higher rate, the aggressiveness also increased with density. The surprising results on infectivity are discussed in the context of current knowledge of plant-pathogen interaction dynamics, as well as neighbour effects on pathogen aggressiveness. Moreover, the results could be useful to develop weed biological control strategies. [ABSTRACT FROM AUTHOR]

In annual plants affected by inflorescence-invading smut pathogens, avoidance of infection is crucial, while in the event of infection, the existence of different degrees of tolerance could also affect the interaction dynamics. Two experiments were performed with Digitaria sanguinalis spikelets vacuum inoculated with ustilospores of Ustilago syntherismae. In the first experiment, they were sown in pots and mature plants were checked to detect internal hyphae. Observations revealed the presence of symptomless mycelium in a few plants. In the second experiment the spikelets, from two different lots, were grown in a chamber. The objective was to explore the importance of two factors in the degree of seedling infection, one genotypic - type of germination ( TG; radicular or coleoptilar) and one environmental - 48 h dark treatment ( DT) applied just after germination. Analysis of the infection frequency showed that all the main effects (seed lot origin, TG and DT) were significant, while interactions were not. For TG, the estimated least square mean infection percentages were 66% for radicular germination and 46% for coleoptilar germination. Darkness increased seedling infection by 25%. Differences between TG, DT and their relationship with mesocotyl length exposed to the germinating spores are discussed. [ABSTRACT FROM AUTHOR]

Copyright of Revista Caatinga is the property of Revista Caatinga and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: From their introduction in 1996, glyphosate resistant (GR) soybean cultivars have been rapidly adopted by farmers in Argentina and in other countries in the world. The high rate of adoption of this technology seems to be based on the simplicity of use provided by a single herbicide (glyphosate), its high efficacy to control many weeds and, the low costs of the technology relative to that used in conventional crops. During 2001–2002, 2002–2003 and 2003–2004 soybean growing seasons, field surveys and field experiments were performed with the aim of studying the effect of different glyphosate management strategies on the diversity of soybean weed communities, weed control, individual survival, fecundity and crop yield. In addition, the emergence pattern of three important weeds, Digitaria sanguinalis, Cyperus rotundus and Anoda cristata, was also studied. Both field surveys and field experiments were carried out on no-till soybean crops sown immediately after wheat or barley harvest (double cropped system). Experiments were set up in commercial soybean crops and consisted of different times of a single glyphosate application, two glyphosate applications and also the application of glyphosate plus a residual herbicide imazethapyr. A. cristata, D. sanguinalis, Stellaria media, Chenopodium album and Cyperus sp. were the most prevalent weeds recorded at pre-harvest of the soybean crops, showing regional constancy higher than 80% in both years. In three out of four field experiments, crop yield was not increased when glyphosate was applied twice compared with a single application of the herbicide. In addition there was a lower negative effect on weed species richness when glyphosate was applied once during the crop cycle than with two applications of glyphosate or glyphosate plus imazethapyr. D. sanguinalis escaped the glyphosate early treatment because of the long weed emergence period, while A. cristata and C. rotundus survived treatments due to their high individual tolerance. The results suggest that it is possible to manage glyphosate application to get high crop yield with a low impact on weed diversity, depending on the weed species and their abundance. [Copyright &y& Elsevier]

The article presents a study which examines the effects of mesotrione on Digitaria sanguinalis or large crabgrass under a diversified environmental condition. It highlights the consistent effect of mesotrione in large crabgrass which was tested between different temperature and irradiance levels. It notes that treated plant bleaching decreased by 21 days after treatment (DAT). Furthermore, it stresses the possible effectiveness of secondary applications of mesotrione after 21 DAT in controlling large crabgrass.

Experiments were conducted to compare growth characteristics, biomass production and glucosinolate content of seven autumn-planted glucosinolate-producing cover crops that were terminated the following spring. The control of Digitaria sanguinalis and Amaranthus palmeri following cover crop incorporation into soil was characterised and fruit yields of bell pepper transplanted into cover crop-amended soil were determined. Differences in glucosinolate concentration and composition were noted between cover crop roots and shoots and among cover crops. Total biomass production by cover crops ranged from 103 g m−2 for garden cress to 894 g m−2 for Indian mustard (F-E75), but cover crop biomass was not correlated with D. sanguinalis and A. palmeri control. D. sanguinalis and A. palmeri control in bell pepper varied by cover crop. D. sanguinalis control by cover crops ranged from 38% to 79%, and A. palmeri control was 23% to 48% at 4 weeks after transplanting (WATP) bell pepper in 2004. D. sanguinalis control was positively correlated with total glucosinolate production, but A. palmeri control was not. D. sanguinalis control in 2005 ranged from 0% to 38% at 2 WATP. In the absence of weeds, cover crops did not negatively affect fruit yields which were often higher than in the absence of a cover crop. Glucosinolate-producing cover crops are not a stand-alone weed management strategy, but some will provide early season control of D. sanguinalis and A. palmeri without having a negative effect on transplanted bell pepper. [ABSTRACT FROM AUTHOR]

Abstract: Drechslera gigantea, a fungal pathogen isolated from large crabgrass (Digitaria sanguinalis) and proposed as a potential mycoherbicide of grass weeds, produces phytotoxic metabolites in liquid and solid cultures. Ophiobolin A and three minor ophiobolins i.e., 6-epi-ophiobolin A, 3-anhydro-6-epi-ophiobolin A and ophiobolin I were obtained from the liquid culture broths. Interestingly and unexpectedly, ophiobolins also appeared in cultures of this fungus and they were isolated together with the known ophiobolins B and J, and designed as ophiobolin E and 8-epi-ophiobolin J. They were characterized using essentially spectroscopic methods. It is noteworthy that D. gigantea produces such a plethora of bioactive organic substances. Some structure-activity relationship results are also discussed in this report. [Copyright &y& Elsevier]

A pathogen isolated from lesions on blighted leaves of crabgrass in three different locations of China was identified as Curvularia eragrostidis . Isolate QZ-2000 was the most virulent of six isolates tested. Experiments on morphology, pathogenicity, effect of environmental factors, and host-range of isolate QZ-2000 were conducted in the laboratory, greenhouse and field to assess the potential of this isolate as a biocontrol agent for grassy weeds. Pathogenicity was quantitatively determined based on mortality and dry-weight reduction of infected large crabgrass. Inoculum concentration, rapeseed oil concentration in formulaton, post-inoculation dew temperature and duration, and plant growth age all significantly influenced the efficacy of the isolate. A total of 85-100% control of large crabgrass was obtained when inoculum concentrations were ≥1×10 6 conidia mL -1 , oil concentrations ≥0.9% (v/v), dew period ≥24 h and air temperatures 20-30°C in the greenhouse. A total of 51 plant species in 20 families were screened against isolate QZ-2000 in host-range studies. Six other species of grassy weeds were susceptible to isolate QZ-2000, but no mortality or significant dry-weight reduction was observed for maize (Zea mays), rice (Oryza sativa), soya bean (Glycine max), cotton (Gossypium hirsutum), or any other economically important crops and plants. In field trials, with 5×10 6 conidia mL -1 inoculum density, 60-7% reduction in dry weight was achieved for large crabgrass seedlings under natural dew-free conditions. These results indicate that isolate QZ-2000 is a potential microbial bioherbicide for control of large crabgrass in crops such as corn, soybean, cotton, water-melon, and peanut. [ABSTRACT FROM AUTHOR]

Copyright of American Journal of Potato Research is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Integrated weed management strategies maintain sub-threshold levels of weeds. The remaining weeds may impact the feeding and habitation patterns of both potato leafhoppers and bean leaf beetles in a snap bean agroecosystem. The objective of our study was to determine the effect of interference between snap beans (Phaseolus vulgaris L.) and either redroot pigweed (Amaranthus retroflexus L.) or large crabgrass (Digitaria sanguinalis L.) on populations of potato leafhopper [Empoasca fabae (Harris)] and bean leaf beetle [Cerotoma trifurcata (Forster)]. Plots were seeded with redroot pigweed or large crabgrass at either the same time as snap bean planting (early) or when snap bean had one trifoliate leaf open (late). The weed density averaged two plants per meter of row. Bean leaf beetle populations, snap bean pod damage, and leaf defoliation were lower in weed-free plots compared to those with either early emerging pigweed or crabgrass. Leafhopper nymphs and adults were 31% to 34% less in plots with crabgrass emerging with snap beans compared to those in weed-free snap bean plots. Thus, the effect of sub-threshold densities of pigweed and crabgrass on insect pests in snap bean varied depending on the species and should be considered when deciding to integrate weed management approaches. [ABSTRACT FROM AUTHOR]

Curvularia intermedia, anamorph of the fungus Cochliobolus intermedius, was isolated from diseased crabgrass (Digitaria sp.) plants and evaluated in greenhouse studies for its potential as a microbial herbicide for control of large crabgrass (Digitaria sanguinalis). The objectives were to evaluate the host range of the fungus and to determine mortality and dry-weight reductions of large crabgrass as influenced by concentrations of inoculum and Silwet L-77 (an organosilicone surfactant), post-inoculation dew temperature, and post-inoculation dew duration. In addition, control of large crabgrass growing in mixed stands with soybeans was evaluated. Ninety to 100% control of large crabgrass, as indicated by mortality and dry-weight reduction, was obtained when inoculum concentrations were ⩾1×106 conidia/ml, Silwet L-77 concentrations were ⩾0.1% (v/v), and dew periods were ⩾10 h (20–35 °C). Forty plant species in 10 families were screened against C. intermedia in host-range studies. Species that exhibited mortality and/or significant dry-weight reductions due to fungal inoculations included: redroot pigweed (Amaranthus retroflexus), beet (Beta vulgaris), chenopodium (Chenopodium amaranticolor), wild oat (Avena fatua), broadleaf signalgrass (Brachiaria platyphylla), bermudagrass (Cynodon dactylon), large crabgrass, barnyardgrass (Echinochloa crus-galli), red rice (Oryza sp.), green foxtail (Setaria viridis), shattercane (Sorghum bicolor), johnsongrass (Sorghum halepense), one cultivar of grain sorghum (Sorghum vulgare), and two cultivars of corn (Zea mays). No mortality or significant dry-weight reductions were noted for peanut (Arachis hypogaea), soybean (Glycine max), cotton (Gossypium hirsutum), centipedegrass (Eremochloa ophiuroides), St. Augustinegrass (Stenotaphrum secondatum), zoysiagrass (Zoysia sp.), or 23 other species. When C. intermedia was applied to mixed plantings of soybeans and large crabgrass, 80–96% reductions in dry weight occurred for large crabgrass seedlings. No significant dry-weight reductions were observed for the soybean plants when compared to the control plants. These results indicate that C. intermedia could be a potential microbial herbicide for control of large crabgrass in crops such as soybean, cotton, and peanut. Additional studies are needed to assess the potential for use of C. intermedia for control of Digitaria spp. in turf grasses such as centipedegrass, zoysiagrass, and St. Augustinegrass that exhibited resistance to the fungus. [Copyright &y& Elsevier]