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Abstract: Background: Parthenium hysterophorus L. is one of the top ten worst weeds globally and is recorded in the global database of invasive species. Objective: The current study was aimed to evaluate the herbicidal potential of Alternaria brassicicola (Schwein.) Wiltshire and Alternaria gaisen Nagano. culture filtrates against a problematic weed P. hysterophorus. Methods: A. brassicicola and A. gaisen culture filtrates were tested in vitro against the test weed. A. gaisen culture filtrates were found most effective against the test weed, and this test fungus was partitioned with various fractions viz. n-hexane, chloroform, ethyl acetate and n-butanol were isolated. In vitro bioactivity of these fractions were tested against P. hysterophorus. The most productive n-hexane fraction was subjected to GC-MS analysis, and thirteen compounds were identified. Results: A. gaisen original (100%) and diluted (50%) culture filtrates showed significant herbicidal activity against P. hysterophorus. However, culture filtrates of A. gaisen suppressed the germination, root and shoot growth of the test weed to a greater extent compared with culture filtrates of A. brassicicola . Original culture filtrates of A. gaisen significantly reduced germination of P. hysterophorus by 88% as compared to diluted concentration by 56% in comparison with control. On the other hand, original and diluted culture filtrates of A. brassicicola reduced the germination of P. hysterophorus by 69% and 50%, respectively, over control treatment. The n-hexane fraction was found more effective in suppressing the P. hysterophorus growth as compared to other fractions. Both 0.10% and 0.05% concentrations of n-hexane fraction significantly inhibited P. hysterophorus seedlings germination by 88% and 81%, respectively. The n-hexane fraction was subjected to GC-MS analysis, and thirteen compounds were identified. Among these, ocimene (27.63%); benzene 1-ethyl-3-methyl-(20.30%) and n-hexadecanoic acid (10.27%) were major compounds. Conclusion: The present study concludes that A. gaisen culture filtrate has substantial herbicidal potential against P. hysterophorous.

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Abstract Background Goosegrass is one of the most troublesome weed species in Brazil due to its wide dispersion and the ability to evolve herbicide resistance. Objective Investigate the response of goosegrass accessions from Mato Grosso, Brazil to glyphosate, clethodim, and haloxyfop. Methods Goosegrass seed samples were collected from seventeen production fields (accessions) in Mato Grosso and screened with the recommended label rates of clethodim, haloxyfop-methyl, and glyphosate. Six accessions withstood the label rate of the evaluated herbicides and were subjected to a dose-response study. Out of the six accessions, two were selected for further F1 dose-response investigations due to their ability to survive the label rate of the three herbicides individually. All studies were conducted under greenhouse conditions in a completely randomized design with four replications, and the F1 dose-response study was replicated in time. Results All six accessions investigated in the dose-response study presented ED50 values higher than susceptible plants for control and biomass reduction. Haloxyfop-methyl had the highest resistance ratios, followed by clethodim and glyphosate. The two accessions investigated in the F1 dose-response study were confirmed to be cross-resistant to clethodim and haloxyfop-methyl and showed low-level resistance to glyphosate. Conclusions The continuous reliance of POST herbicides for weed management in Mato Grosso cropping systems has selected goosegrass accessions that can withstand high rates of ACCase-inhibiting herbicides, particularly haloxyfop-methyl. Moreover, two accessions with resistance to ACCase-inhibiting herbicides, clethodim and haloxyfop-methyl, and low-level resistance to glyphosate were identified, suggesting the presence of multiple resistance in goosegrass accessions from Mato Grosso, Brazil.

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Abstract Background The presence of weeds in Roundup Ready® (RR) soybean and corn crops compromises yield. Management practices recommended by the consultants and adopted by producers directly interfere in the occurrence of these species. Objective To survey management practices used in RR soybean and corn fields in the Rio Grande do Sul. Methods Data were gathered via the application of questionnaires during the 2018/19 growing season to consultants working with RR soybean and corn cropping in Rio Grande do Sul state. There were 112 responses, covering about 72 municipalities in the state. Results Technical consultants highlighted Conyza spp. and Lolium multiflorum as the most common weed species and classified resistance to herbicides and advanced stages of weeds at the time of herbicide application as the primary causes of low weed control efficacy. They observed an increase in resistance evolution and a two to three-fold increase in the use of herbicides in glyphosate-tolerant crops. Using a mixture of herbicides was the main recommendation for the management of weeds that escape control, while in areas with proven resistance, crop rotation was the main recommendation. Conclusions Crop rotation and herbicide mixtures are the most recommended management practices, with herbicide resistance and advanced stage of development listed as the main reasons for the difficulties of weed control.

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Abstract Background The limited number of selective herbicides for white oat (Avena sativa L.) cultivation makes it managing weeds a challenge. Currently, few herbicide options are available for selective weed control in winter crops. Previous studies have indicated that ALS-inhibiting herbicides could be potential alternatives, so studies were conducted. Objective To characterize the tolerance level of white oat cultivars to ALS-inhibiting herbicides and to evaluate the level of weed control by applying penoxsulam and bispyribac-sodium. Methods Tolerance (%) was determined for white oat cultivars UFRGS 14, URS Guará, URS Guria, UFRGS 18, and URS Taura for imazethapyr, iodosulfuron, penoxsulam, and bispyribac-sodium dose-response. Also, the control efficiency of different doses of penoxsulam and bispyribac-sodium was determined on weed species of white oat, namely crabgrass (Digitaria horizontalis), siberian motherwort (Leonurus sibiricus), italian ryegrass (Lolium multiflorum), and wild radish (Raphanus raphanistrum). Results Imazethapyr and bispyribac-sodium were the least selective herbicides, whereas iodosulfuron had intermediate selectivity, and penoxsulam was the most selective for the white oat cultivars tested, with average control of 100, 72, 62.7 and 40%, respectively. Overall, bispyribac-sodium had a higher level of weed control (77.1%) than penoxsulam (62%). Label doses of penoxsulam and bispyribac-sodium resulted in low control levels of crabgrass. Conclusions All doses of bispyribac-sodium effectively control wild radish and italian ryegrass. The recommended dose of penoxsulam was selective for some cultivars of white oat and effectively controlled italian ryegrass and wild radish.

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Abstract Background The reserve of viable weed seeds present on the soil surface and scattered throughout the soil profile. Objective A glasshouse study was conducted to determine the special abundance of soil seed bank flora in parthenium invaded maize fields in West Gojjam Zone. Methods The soil samples were collected from 90 fields at 0-5 cm, 5-10 cm and 10-15 cm soil depth with 10 cm width. Results A total of 121 weed species belonging to 27 families were found in the soil seed banks. The most frequent families were Poaceae (31 species), Asteraceae (21 species) and Leguminosae (9 species). The highest importance value was recorded by Parthenium hysterophorus, Ageratum conyzoides and Echinochloa colona with 19.05, 19.02 and 14.37%, respectively at 0-5 cm soil depth. The highest importance values of 20.39, 20.16 and 16.54% were registered by P. hysterophorus, A. conyzoides and Galiansago parviflora, respectively at 5-10 cm soil depth. Likewise, at 10-15 cm soil depth highest importance value was recorded by A. conyzoides, P. hysterophorus and E. colona with 19.12, 17.30 and 116.13%, respectively. The Shannon diversity index at 0-5, 5-10 and 10-15 cm soil depth were 4.46, 4.41 and 4.17, respectively. High similarity (68.10%) was observed between 0-5 and 5-10 and followed by 5-10 and 10-15 cm (60.19%) and 0-5 and 10-15 cm (55.39%). Conclusions These results could help to predict infestation potential and could lead to improved weed management strategies in maize growing areas in the study area.

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Abstract Background: Clearfield® (CL) rice is one of the most successful tools for selective weedy rice control, using imidazolinone herbicides (IMI). However, IMI have residual soil activity and may carryover to non-tolerant crops growing in succession. It is necessary to find options to reduce IMI persistence in paddy rice fields. Objective: Evaluate the effect of water management on IMI dissipation in rice paddy and its carryover to soybean and non-CL rice. Methods: The herbicide mixture of imazapyr and imazapic totalizing 147 g a.i. ha−1 and 49 g a.i. ha−1, respectively, was applied half in preemergence (S3 stage – rice spike stage) and the other half in postemergence (V3-V4 rice stage). After herbicide application, a total of 21 samples were taken for analysis of residues. Soil samples were air dried and herbicides residues were analyzed using high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Results: Calculated field dissipation half-life (DT½) of imazapyr was 182.5 and 42.0 days in continuous flooding and intermittent water management, respectively. Imazapic had a DT½ of 96.3 days on intermittent water management. No adjustment for the dissipation regression parameters was obtained for imazapic in continuous water management. No reduction in yield components was observed in soybean when grown in soil with imidazolinone residues. On the other hand, non-CL rice showed decreased shoot dry weight and stem number. Conclusion: Imidazolinone herbicides have a longer half-life under continuous rice water management than intermittent. Therefore, growers can use intermittent irrigation in ares prone to IMI carryover and can use soybean in rotation.

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Abstract: Background: In Thailand, Echinochloa crus-galli (L.) P. Beauv. (barnyardgrass) is the most problematic weed in rice. Quinclorac was first commercialized in 1997 in Thailand and became the primary herbicide option for barnyardgrass control. The intensive use of quinclorac in rice fields increases the risk of the evolution of resistant barnyardgrass. Objective: This study was conducted to survey the occurrence of quinclorac-resistant barnyardgrass in Thailand, investigate the levels of quinclorac resistance, and evaluate alternative control measures for quinclorac-resistant barnyardgrass. Methods: Seeds of barnyardgrass were collected from 165 rice fields, located in 27 provinces of Thailand, and screened for quinclorac resistance. A whole-plant dose-response study was conducted on a susceptible population and three resistant populations to evaluate the resistance level. In addition, effectiveness of alternative herbicides including bispyribac, fenoxaprop, penoxsulam, profoxydim, propanil, and pyribenzoxim were evaluated using the selected populations. Results: Quinclorac-resistant barnyardgrass was identified in 121 rice fields (73%). Five sites (3%) exhibited developing barnyardgrass resistance to quinclorac whereas barnyardgrass populations in thirty-nine sites (24%) were susceptible to quinclorac. The evaluated resistant populations were at least 93-fold more resistant to quinclorac than the susceptible population. Profoxydim and propanil provided effective control of the two quinclorac-resistant barnyardgrass populations. One population (B56) exhibited no shoot biomass reduction after treatment either with quinclorac or bispyribac, suggesting multiple resistance to auxin mimics and ALS-inhibiting herbicides. Conclusions: Quinclorac-resistant barnyardgrass cases were confirmed in Thailand. The resistant barnyardgrass populations were broadly distributed on major rice-production areas of Thailand. Multiple-resistance in a quinclorac resistant population requires further investigation.

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Abstract Background Weeds have high spatial variability and show clustering behavior, with heterogeneity in scales that can be evaluated through multifractal analysis. Objective The objective of this study was to evaluate the spatial variability of weeds using multifractal analysis in a no-till area. Methods Sampling was conducted at 1,015 sampling points in an experimental plot with a regular grid of 5 × 5 m (2.38 ha) with no tillage. The area was cultivated with triticale (Triticum secale), and in the summer of 2011, the area was cultivated with soybean (Glycine max). Data were analyzed using descriptive statistics and multifractal analysis using the box-counting method to determine the scaling properties of the variables. Results The predominance of Raphanus raphanistrum was identified in the winter crop and Commelina ssp. during the summer. The singularity spectrum showed greater asymmetry for Raphanus raphanistrum and Commelina ssp. in relation to the category of other weeds (OW). The degree of multifractality varied throughout the study period, showing the ecological patterns of the studied species. Scale heterogeneity was revealed, with different degrees of multifractality that evidenced the processes of dispersion and colonization of the environment by the different weed species evaluated. Conclusions The species Raphanus raphanistrum and Commelina ssp. showed domains of low measurement values, and OW was the most heterogeneous.

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Abstract Background Quinclorac- main herbicide targeting to barnyard grass, has been used for decades in rice fields. Echinochloa species have been reported evolving into quinclorac resistance.Objective: Quinclorac resistance and its mechanism remain undisclosed in Echinochloa oryzoides (Ard.) Fritsch that needs to be uncovered. Methods Dose-response assays were performed, followed by ethylene synthesis, and related enzyme activities along with gene transcription were studied. β-CAS activity and its molecular docking were investigated. Results E. oryzoides evolved into 21 times resistance to quinclorac from Jiangsu province of China. The increment in ethylene levels in this biotype was correlated negatively with the level of resistance and positively with quinclorac-induced growth inhibition. Ethylene response pathway determination showed that resistant biotype decreased 1-aminocyclopropane-1-carboxylic acid (ACC) contents, related enzyme activities, and transcription of ACS and ACO genes. These results indicated that ethylene biosynthesis inhibition and quinclorac resistance possessed a positive correlation. Resistant biotype exhibited ~ 2-fold more β-CAS activity than susceptible ones. Resistant EcCAS gene depicted nucleotide changes as compared to susceptible ones, which resulted in two amino acid substitutions (Met-287-Lys and Thr-352-Ala). Consequently, resistant β-CAS enzyme exhibited an increase in binding residue in active site (simulation modelling); that can be the probable reason for higher enzyme activity in the resistant biotype. Conclusions The study concludes that variation in response pathway of auxin and potentially improved cyanide degradation were plausible mechanisms endowing quinclorac resistance in E. oryzoides .

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Abstract Background Aroeira or Brazilian peppertree, Schinus terebinthifolia Raddi (Anacardiaceae: Rhoeae), is one of the worst invasive plants in California, Florida, and Hawaii, USA because of its wide distribution, adaptation to various habitats, toxicity, and demonstrated negative impacts on biodiversity. Chemical and mechanical methods provide only temporary control, are expensive, may damage native plants, and often create disturbance conducive to reinvasion by Brazilian peppertree and other invasive weeds. The leaflet galling psyllid Calophya terebinthifolii Burckhardt & Basset (Calophyidae: Calophyinae) is native to South America and recent studies have shown this insect attacks only Brazilian peppertree. Nymphs complete their development in open pit galls that create nutrient sinks, which divert resources away from normal plant growth and reproduction. Objective The objective of this study was to confirm the biological control potential of C. terebinthifolii . Methods We used a randomized complete block design with four treatments (chemical exclusion [control], natural infestation, low and high psyllid densities) replicated in space. Results At low densities, C. terebinthifolii significantly reduced flower production by 80.6% and 93.9%, respectively, compared to the chemical exclusion treatment. At high densities, the psyllid completely inhibited fruit production. Furthermore, leaf and stem biomass were significantly reduced following sustained attack by the psyllid C. terebinthifolii . Conclusions Overall, our results confirmed that feeding damage by this psyllid negatively impacts above ground vegetative growth and reproduction of Brazilian peppertree. Therefore, C. terebinthifolii should be considered for introduction into Florida for biological control of this invasive shrub.

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Abstract Background Transferring herbicide resistance genes to plant cultivars is one of the most effective methods for managing weed growth in agricultural land. The RePAT gene, previously isolated from the marine bacterium Rhodococcus sp . strain YM12, was found to provide glufosinate resistance to plants. Objective In this study, we further investigated the protein structure and function of RePAT isolated from the marine. Methods The physicochemical properties, two-dimensional structure, three-dimensional structure, and functional domains of the RePAT protein were analyzed and predicted using bioinformatics tools, and RePAT was optimized according to codon bias present in Arabidopsis thaliana . Site-directed mutagenesis of RePAT was performed, and the wild-type ( RePAT ) and mutant ( RePAT V120I ) genes were successfully transferred into A. thaliana . Results Our results showed that RePAT was an unstable hydrophilic protein, and six phosphorylation sites and two N-glycosylation sites were predicted. In addition, conserved domains containing the NAT_SF super family and coenzyme A-binding pocket were predicted in RePAT. Transgenic experiments and glufosinate resistance assays showed that the glufosinate resistance of A. thaliana containing the mutant gene ( RePAT V120I ) was lower than that of plants containing the wild-type gene, indicating that the missense mutation in RePAT V120I had a significant effect on its glufosinate resistance. Conclusions Our study provided improvement result for knowing the transferring herbicide resistance gene RePAT .

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Abstract Background This manuscript presents data of screening and dose-response curves of a goosegrass population from Primavera do Leste, MT, Brazil, which results in the first official report of multiple resistance of goosegrass to ACCase and EPSPs inhibiting herbicides in Brazil. Objective Evaluate the control of a goosegrass population from Primavera do Leste, MT, Brazil, suspected of resistance to the glyphosate, fenoxaprop-p-ethyl, and haloxyfop-methyl herbicides, using dose-response curves. Methods The study was carried out in two stages, the first in Brasília, DF, Brazil, and the second in Piracicaba, SP, Brazil. The first stage consisted in the initial evaluation and identification of resistance, which was confirmed in the second. In the first stage, the herbicides glyphosate, fenoxaprop-p-ethyl, and haloxyfop-methyl were applied to susceptible and resistant goosegrass populations (F1 and F2 generations) with plants with 2 and 3 tillers, using nine rates (0, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 times the recommended rate). In the second stage, the herbicides were applied to susceptible and resistant populations with plants with 4 leaves, using 12 rates (0, 0.03125, 0.0625, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, and 32 times the recommended rate). Results The high sensitivity of susceptible plants combined with the high resistance level of resistant ones resulted in high resistance factors for fenoxaprop-p-ethyl and haloxyfop-methyl, with values greater than 27.8. The resistance factor for glyphosate ranged from 3.3 to 11, depending on growth stage at application time. Conclusions The goosegrass population from Primavera do Leste, MT, Brazil, presented resistance to EPSPs (glyphosate) and ACCase (haloxyfop-methyl and fenoxaprop-ethyl) inhibiting herbicides.

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Abstract Background Phytosociological surveys of weeds in agricultural regions, such as the coffee growing Cerrado Mineiro Denomination, are essential for understanding the predominant species in a cultivation area. Objective This study aimed to determine the predominant weed species in coffee crops in Cerrado Mineiro through phytosociological surveys during two periods of the year. Methods 26 coffee farms in 12 municipalities within the Cerrado Mineiro Denomination of Origin of were visited. The inventory square method was used for the phytosociological surveys. In each area, 40 m2 was evaluated and divided into two study periods (summer and winter). Calculations of the variables were performed using the following data: frequency, density, abundance, importance value index, similarity coefficient, rarefaction curve, Shannon index, and hierarchical grouping analysis using Jaccard’s similarity. Results In the summer (rainy period), 54 species from 16 families were found, with Poaceae, Asteraceae, and Amaranthaceae predominating. In winter (dry season), 56 species from 16 families were found, predominantly Asteraceae, Poaceae, and Brassicaceae. There was a predominance of 17 and 16 species, with similarity levels (Jaccard) of 45.58% and 40.78% for summer and winter, respectively. Conclusions The weed community in the Cerrado Mineiro coffee plantation is dominated by two main families, Poacaeae and Asteraceae, with Eleusine indica (summer) and Conyza spp. (winter) being the species with the highest importance values.

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Abstract Background Dicamba is a herbicide with a moderate volatility profile and low dose effects on broadleaf weeds. Dicamba volatility can be strongly reduced with formulation technology and volatilization reducers. Objective This literature review on the dicamba herbicide aims to present new perspectives for its use, characteristics, volatilization risks, technologies to mitigate these risks and the main methods used to assess volatility in Brazil and worldwide. Conclusions Dicamba volatility can be mitigated with appropriate formulations and/or the use of adjuvants to reduce volatility. There has been an evolution in adapting new salts and technologies to reduce dicamba volatility. There are different methods of evaluating herbicide volatility, in particular, for the quantification of volatilized dicamba either in laboratory or field studies. Available methods can be fast and consistent and can assess volatilization from different surfaces, weather conditions and technologies to reduce volatilization. Under some conditions it is desirable to combine this method with bioassays.

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Abstract Background Populations of yam dry rot nematodes Scutellonema bradys, Pratylenchus coffeae and P. brachyurus can be sustained on weed hosts. Objective Evaluate the reaction of 10 weeds frequently found in Alagoas to P. coffeae under greenhouse conditions. Methods Two experiments were carried out in a completely randomized design, with 11 treatments, constituted of 10 weed species and the control (Dioscorea cayenensis) with eight replications. Plants were inoculated with 2,000 nematode specimens, nematode populations were evaluated in roots and soil 60 days after inoculation and the reproduction factor (RF) defined as RF = final population/initial population was calculated. Results Euphorbia hyssopifolia showed RF=0 and was considered as non-host, whereas Chenopodium album, Amaranthus sp., Panicum maximum, Eleusine indica, Senna occidentalis, Emilia coccinea and Richardia brasiliensis, showed RF<1, being rated as poor hosts. Ricinus communis and Macroptilium lathyroides showed RF>1 only in the second trial and were classified as good hosts. Conclusion Ricinus communis and M. lathyroides are potential sources of nematode inoculum for dry rot disease development.

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Abstract Background Eragrostis plana is the main invasive plant in the Pampa Biome of southern Brazil. This plant is highly competitive, tolerant to abiotic stresses, and very difficult to manage. Plants exposed to abiotic stresses and herbicides develop mechanisms that help alleviate or reduce damage caused by stressors and transmit this ability to the progenies. Objective The study’s objectives were to ascertain whether acclimatization to stress due to drought and sub-lethal doses of glyphosate may decrease plant sensitivity to glyphosate and investigate the possible memory mechanisms involved in this process. Methods A population of E. plana was submitted to drought, glyphosate, or a combination of drought plus glyphosate for two generations. The progenies were analyzed for sensitivity to the herbicide glyphosate and for biochemical, metabolites, and molecular responses. Results When testing sensitivity to glyphosate in the G 2 generations, the DRYxGLY (plants stressed with drought plus glyphosate) was the least sensitive (ED50 443.0 g a.e. ha-1), while CHK (without stresses) was the most sensitive (ED50 278.0 g a.e. ha-1). Evaluating the effects of glyphosate, the CHK population showed a greater accumulation of oxidative damage and shikimic acid. While DRYxGLY had greater antioxidant activity and higher expressions of the EPSPS and ABC-carrier MRP10 genes. Conclusions Recurrent selection with drought stress and sub-lethal rate of glyphosate (DRYxGLY) showed reduced sensitivity to glyphosate in the second generation ( G 2 ). The conjunction of factors, including the upregulation of EPSPS and the ABC MRP10 transporter, antioxidant enzymes seem to decrease the sensitivity of the DRYxGLY population to glyphosate.

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Abstract Background Glyphosate is the most effective herbicide to control the invasive and perennial Eragrostis plana in Southern Brazil. However, one application has not been sufficient to prevent the regrowth of plants.Objective: The aim of this research was to evaluate the efficacy of glyphosate sprayed alone or mixed with fluazifop-p-butyl or flumioxazin on E. plana control and to investigate 14C-glyphosate absorption and translocation. Methods Plants with 2-3 tillers were treated with glyphosate (700 g a.e. ha-1), fluazifop-p-butyl (47 g a.i. ha-1), flumioxazin (100 g a.i. ha-1), glyphosate + fluazifop-p-butyl (700 g a.e. ha-1 + 47g a.i. ha-1), glyphosate + flumioxazin (700 g a.e. ha-1 +100 g a.i. ha-1). Weed control was evaluated visually for 28 d after treatment (DAT) when plants were harvested for shoot dry biomass determination. 14C-glyphosate absorption and translocation were measured at 24 and 72 h after treatment. Results Glyphosate at 700 g a.e. ha-1 controlled E. plana plants at 2-3 tillers. The mixture with fluazifop-p-butyl or flumizin did not significantly increase the level of control (87 and 86% at 7 DAT, respectively) but increased 14C-glyphosate translocation to the roots. Conclusions Glyphosate is effective on E. plana. However, applied with fluazifop-p-butyl could improve the control of this weed, especially when perennial plants of E. plana dominate the field, preventing their fast regrowth.

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Abstract Background The presence of straw on the soil contributes to the management of weeds in several production systems and this understanding needs to be extended to annual crops under no-tillage systems. Objective This study aimed to evaluate the effect of covering the soil with 5 Mg ha-1 of maize straw on the germination and growth of Digitaria insularis, Conyza spp., Bidens pilosa, Amaranthus hybridus, Euphorbia heterophylla, and Eleusine indica. Methods For this purpose, completely randomized design was used with sixteen and third two replicates. Four assays were conducted between the years 2019 and 2020 in a greenhouse. The number of emerged seedlings was evaluated at 7, 14, and 21 days after sowing (DAS) and the shoot dry weight of the seedlings and the correlation between these variables were evaluated at 21 DAS. Results The covering of the soil with straw decreased the weed infestation of all species, except E. heterophylla, which presented positive correlation for the variables evaluated, denoting that the straw had no effect on the germination and growth of this species. The variables evaluated showed no correlation for the other species, denoting that the soil cover with straw suppress the germination and growth of plants. Conclusions We conclude that soil cover with 5 Mg ha-1 of maize straw is a tool for the control of weeds of the species evaluated, except E. heterophylla, and an option for integrated weed managements that can complement the residual effect of herbicides.

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Abstract: Due to the negative environmental effects of herbicides, restrictions are imposed in many developed countries and the transition to alternative methods is encouraged. Upon these restrictions and prohibitions, non-chemical weed control methods have been started to be developed. One of these alternative weed control methods is the electric current method. Background: Using multiple electrodes, the mortality rates were measured by exposing the plants germinated in laboratory conditions to AC and DC currents for different periods. Objective: In this study, the effects of direct current (DC) and alternating current (AC) on the mortality rates of plants were investigated. Methods: By comparing the NDVI (normalized difference vegetation index) values measured before and 1 week after the plants were exposed to electrical current, the effect of AC/DC on the mortality rate was determined. Results: While mortality was between 11% and 17% for AC, mortality occurred at a rate of 31% in plants that had 300 volts DC applied for 350 s. Conclusions: The degrees (r) of these relationships were 79.7% and 95.7%, respectively. According to these results, mortality rates increased as the voltage increased.

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Abstract: Background: Eragrostis plana is an invasive plant in native grassland areas associated with degradation of the Pampa biome. Selective control of E. plana is difficult due to its similarity to other grassland species. There is a lack of information about E. plana control using selective herbicide application equipment. Objective: The present study aimed to evaluate the efficacy of a pressurize rope wick applicator for controlling the invasive plant E. plana as function of different salts of glyphosate, application volumes, and year seasons. Methods: The studies were carried out under field conditions and repeated. The first study evaluated glyphosate salts of isopropylamine, dimethylamine, monoammonium, diammonium, and potassium at doses of 720 and 1440 g ha-1 and clethodim at 60 and 120 g ha-1. The second study assessed application volumes of 8, 24, 40, and 56 L ha-1 using isopropylamine and potassium salts of glyphosate. Results: Glyphosate applied in summer was more effective at controlling E. plana, with less regrowth than glyphosate application in winter. The glyphosate diammonium was more effective at controlling E. plana than isopropylamine, dimethylamine, monoammonium, or potassium salt formulations at 1440 g ha-1. Application volume of glyphosate between 8 and 40 L ha-1 provided similar control of E. plana and pasture selectivity. Conclusions: Glyphosate applied with a rope wick selective applicator was effective in controlling E. plana clumps and was selective to grassland. The control efficacy varied as a function of glyphosate salts and year season, but not due to application volume of 8 and 40 L ha-1.

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ABSTRACT Background: Cyperus aromaticus (Navua sedge) is a creeping perennial sedge common to tropical environments, currently threatening many agroecosystems and ecosystems in Pacific Island countries and northern Queensland in Australia. Objective: A glasshouse study was conducted to evaluate the efficacy of florpyrauxifen-benzyl on C. aromaticus plants with and without established rhizomes. Methods: The plants with established rhizomes were treated at three application times being mowed, pre-flowering and flowering growth stages and plants without established rhizomes were treated at seedling, pre-flowering and flowering growth stages. At each application time, plants were treated with four rates of florpyrauxifen-benzyl: 0, 15, 30 and 60 g a.i. ha−1 and control. Results: There was no mortality in the plants with established rhizomes. Reduction in the number of tillers was observed at four weeks after treatment (WAT) in plants treated with 30 and 60 g a.i. ha−1 of herbicide, however, there was new growth from the rhizomes and the number of tillers increased at 8 WAT. Conversely, florpyrauxifen-benzyl provided above 95% control in plants without established rhizomes. Conclusions: These results indicate florpyrauxifen-benzyl can help manage a new C. aromaticus infestation prior to the establishment of rhizomes. However, it has little to no impact on C. aromaticus plants with established rhizomes, and other management options should be employed to control them.

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Abstract: Background: Ryegrass is considered an important weed in crops in the state of Rio Grande do Sul, Brazil, for being resistant to the herbicide glyphosate. Objective: This study evaluates ryegrass control by applying different spray volumes and doses of clethodim alone or in combination with glyphosate and/or 2,4-D. Methods: Two field experiments were conducted in a 5 x 3 factorial design. In experiment I, factor A consisted of clethodim (96 g a.i. ha-1); clethodim (96 g a.i. ha-1) + glyphosate (1,080 g a.e. ha-1); clethodim (96 g a.i. ha-1) + 2,4-D (1,047 g a.e. ha-1); clethodim (96 g a.i. ha-1) + glyphosate (1,080 g a.e. ha-1) + 2,4-D (1,047 g a.e. ha-1); and control without treatment. Factor B consisted of three spray volumes (40, 80, and 120 L ha-1). In the second experiment, factor A consisted of the same herbicides and their associations aforementioned and factor B consisted of three increasing doses of the herbicide clethodim (96, 192 and 288 g a.i. ha-1). The herbicides were applied at the milky stage of ryegrass grains. Ryegrass control at 10, 20, and 30 days after application (DAA) of herbicides and dry matter were evaluated. Results: Spray volume reduction did not interfere with ryegrass control by clethodim and glyphosate or clethodim, glyphosate, and 2,4-D at 30 DAA, but it did interfere with the application of clethodim alone or associated only with 2,4-D. Doses above 192 g a.i. ha-1 of clethodim alone or in mixture were efficient for ryegrass control. Conclusions: Greater clethodim doses and spray volume increased control of ryegrass at the milky grain stage and decreased the antagonism in the associations with 2,4-D.

Resumo em Inglês:

Abstract Background The use of glyphosate on glyphosate-tolerant soybean crops led to improved control of a wide range of weeds, which resulted in reduced costs with the no-till system. The emergence of the first herbicide-resistant weeds have driven an increase in glyphosate applications, and even though those soybean materials have a low sensitivity to glyphosate, the rhizobial symbionts could be affected by the herbicide, and plants might be indirectly injured. Objective This study aimed to determine the effect of multiple glyphosate applications throughout the soybean crop cycle on plant growth, nodulation and biological nitrogen fixation (BNF). Methods The effects of one, two and three treatments of a recommended dose of glyphosate on BNF and growth of glyphosate-tolerant soybean plants were evaluated in greenhouse and field experiments. Results Two or more applications of glyphosate inhibited the BNF and growth of soybean plants. Under controlled conditions, at least one glyphosate application at V1 affected the number and mass of nodules per plant, and successive applications in advanced phonological stages resulted in the inhibition of nodule growth. With two and three sprayings of glyphosate, the proportion of N derived from the air in plants was reduced by 41% compared with the treatment without glyphosate. In field experiments, detrimental effects of three sequential applications of glyphosate on number of nodules per plant (-25%), biomass production (-21%) and grain yield (-36%) were detected. Conclusions Multiple glyphosate applications of glyphosate inhibited the BNF and growth of soybean plants and it could be as damaging as +weed interference. Nomenclature: Glyphosate; soybean, Glycine max (L.) Merril

Resumo em Inglês:

Abstract Background The use of carbonaceous materials for environmental remediation is attractive due to low expense and high sorption capacity. However, their efficiency in contaminant removal is affected by substrate composition and sorption mechanism. Objective This study investigated atrazine sorption and desorption in three carbon-rich substrates. Data were evaluated considering isotherm models and sorbent chemical composition. Methods Sorption was performed by the batch equilibrium method with three substrates obtained from pig slurry composting with different proportions (w/w) of charcoal fines (CF): CF0, CF9 (9% CF), and CF18 (18% CF). The substrates were characterized by elemental analysis, 13C NMR CP/MAS spectroscopy. The Freundlich and Dubinin-Radushkevich (DRK) models better fitted the sorption data (0.96>R2>0.81), followed by Temkin (0.95>R2>0.76). Charcoal addition to composting substrates increased carbon content and the aromaticity in the order CF0<CF9< CF18. However, the sorption affinity decreased in the opposite order as indicated by the Kf values: 675, 335 and 290 L kg-1, respectively. Values of the E parameter (DRK) varied from 8.05 to 8.29 kJ mol-1, suggesting a predominant physical sorption mechanism, whereas the Bt coefficient (Temkin) indicated an endothermic process. Desorption was only observed at higher atrazine concentrations (>10 mg L-1), and the desorption Kf values were greater than the respective sorption values. Conclusions Atrazine sorption in the tested C-rich substrates is not governed by the carbon content or aromaticity. The low sorption reversibility implies a low atrazine mobility from the tested substrates and suggests their potential for herbicide removal in the environment.