Amaranthus retroflexus L. is one of the malignant weeds which can cause a reduction in the soybean yield. We found a population of A. retroflexus (R-Q) resistant to fomesafen through the initial screening of whole-plant dose response bioassay in the research. The resistance index of the population (R-Q) was 183 times of the sensitive population (S-N). The resistant and sensitive populations were used as experimental materials in the paper. Strand-specific RNA-Seq analyses of R‒Q and S‒N populations obtained from herbicide-treated and mock-treated leaf samples after treatment were conducted to generate a full-length transcriptome database. We analyzed differentially expressed genes (DEGs) among the R-Q and S‒N A. retroflexus populations treated with recommended dose and mock-treated on the 1st (24 h) and 3rd (72 h) days to identify genes involved in fomesafen resistance. All 82,287 unigenes were annotated by Blastx search with E-value < 0.00001 from 7 databases. A total of 94,815 DEGs among the three group comparisons were identified. Two nuclear genes encoding PPO (PPX1 and PPX2) and five unigenes belonging to the AP2-EREBP, GRAS, NAC, bHLH and bZIP families exhibited different expression patterns between individuals of S‒N and R-Q populations. The A. retroflexus transcriptome and specific transcription factor families which can respond to fomesafen in resistant and susceptible genotypes were reported in this paper. The PPX1 and PPX2 genes of the target enzyme were identified. The study establishes the foundation for future research and provides opportunities to manage resistant weeds better.

The herbicides glyphosate (Gly) and imazamox (Imx) inhibit the biosynthesis of aromatic and branched-chain amino acids, respectively. Although these herbicides inhibit different pathways, they have been reported to show several common physiological effects in their modes of action, such as increasing free amino acid contents and decreasing soluble protein contents. To investigate proteolytic activities upon treatment with Gly and Imx, pea plants grown in hydroponic culture were treated with Imx or Gly, and the proteolytic profile of the roots was evaluated through fluorogenic kinetic assays and activity-based protein profiling.

Photosystem II (PSII) herbicides have been detected in nearshore tropical waters such as those of the Great Barrier Reef and may add to the pressure posed by runoff containing sediments and nutrients to threatened seagrass habitats. There is a growing number of studies into the potential effects of herbicides on seagrass, generally using large experimental setups with potted plants. Here we describe the successful development of an acute 12-well plate phytotoxicity assay for the PSII herbicide Diuron using isolated Halophila ovalis leaves. Fluorescence images demonstrated Diuron affected the entire leaf surface evenly and responses were not influenced by isolating leaves from the plant. The optimum exposure duration was 24 h, by which time the inhibition of effective quantum yield of PSII (∆F/F(m)') was highest and no deterioration of photosystems was evident in control leaves. The inhibition of ∆F/F(m)' by Diuron in isolated H. ovalis leaves was identical to both potted and hydroponically grown plants (with leaves remaining attached to rhizomes), indicating similar reductions in photosynthetic activity in these acute well-plate assays. The sensitivity of the assay was not influenced by irradiance (range tested 40 to 400 μmol photons m(-2) s(-1)). High irradiance, however, caused photo-oxidative stress in H. ovalis and this generally impacted in an additive or sub-additive way with Diuron to damage PSII. The bioassay using isolated leaves is more rapid, uses far less biological material and does not rely on specialised aquarium facilities in comparison with assays using potted plants. The development and validation of this sensitive bioassay will be useful to reliably screen and monitor the phytotoxicity of existing and emerging PSII herbicides and contribute to risk assessments and water quality guideline development in the future.

Urena lobata is becoming a noxious and invasive weed in rangelands, pastures, and undisturbed areas in the Philippines. This study determined the effects of seed scarification, light, salt and water stress, amount of rice residue, and seed burial depth on seed germination and emergence of U. lobata; and evaluated the weed's response to post-emergence herbicides. Germination was stimulated by both mechanical and chemical seed scarifications. The combination of the two scarification methods provided maximum (99%) seed germination. Germination was slightly stimulated when seeds were placed in light (65%) compared with when seeds were kept in the dark (46%). Sodium chloride concentrations ranging from 0 to 200 mM and osmotic potential ranging from 0 to -1.6 MPa affected the germination of U. lobata seeds significantly. The osmotic potential required for 50% inhibition of the maximum germination was -0.1 MPa; however, some seeds germinated at -0.8 MPa, but none germinated at -1.6 MPa. Seedling emergence and biomass increased with increase in rice residue amount up to 4 t ha(-1), but declined beyond this amount. Soil surface placement of weed seeds resulted in the highest seedling emergence (84%), which declined with increase in burial depth. The burial depth required for 50% inhibition of maximum emergence was 2 cm; emergence was greatly reduced (93%) at burial depth of 4 cm or more. Weed seedling biomass also decreased with increase in burial depth. Bispyribac-sodium, a commonly used herbicide in rice, sprayed at the 4-leaf stage of the weed, provided 100% control, which did not differ much with 2,4-D (98%), glyphosate (97%), and thiobencarb + 2,4-D (98%). These herbicides reduced shoot and root biomass by 99-100%.

The continuous and sole dependence on imidazolinone (IMI) herbicides for weedy rice control has led to the evolution of herbicide resistance in weedy rice populations across various countries growing IMI herbicide-resistant rice (IMI-rice), including Malaysia. A comprehensive study was conducted to elucidate occurrence, level, and mechanisms endowing resistance to IMI herbicides in putative resistant (R) weedy rice populations collected from three local Malaysian IMI-rice fields. Seed bioassay and whole-plant dose-response experiments were conducted using commercial IMI herbicides. Based on the resistance index (RI) quantification in both experiments, the cross-resistance pattern of R and susceptible (S) weedy rice populations and control rice varieties (IMI-rice variety MR220CL2 and non-IMI-rice variety MR219) to imazapic and imazapyr was determined. A molecular investigation was carried out by comparing the acetohydroxyacid synthase (AHAS) gene sequences of the R and S populations and the MR220CL2 and MR219 varieties. The AHAS gene sequences of R weedy rice were identical to those of MR220CL2, exhibiting a Ser-653-Asn substitution, which was absent in MR219 and S plants. In vitro assays were conducted using analytical grade IMI herbicides of imazapic (99.3%) and imazapyr (99.6%) at seven different concentrations. The results demonstrated that the AHAS enzyme extracted from the R populations and MR220CL2 was less sensitive to IMI herbicides than that from S and MR219, further supporting that IMI herbicide resistance was conferred by target-site mutation. In conclusion, IMI resistance in the selected populations of Malaysian weedy rice could be attributed to a Ser-653-Asn mutation that reduced the sensitivity of the target site to IMI herbicides. To our knowledge, this study is the first to show the resistance mechanism in weedy rice from Malaysian rice fields.

Acetohydroxyacid synthase (AHAS), also called acetolactate synthase, is a key enzyme involved in the first step of the biosynthesis of the branched-chain amino acids valine, isoleucine and leucine. Acetohydroxyacid synthase-inhibiting herbicides (AHAS herbicides) are five chemical families of herbicides that inhibit AHAS enzymes, including imidazolinones (IMI), sulfonylureas (SU), pyrimidinylthiobenzoates, triazolinones and triazolopyrimidines. Five AHAS genes have been identified in rapeseed, but little information is available regarding the role of miRNAs in response to AHAS herbicides. In this study, an AHAS herbicides tolerant genotype and a sensitive genotype were used for miRNA comparative analysis. A total of 20 small RNA libraries were obtained of these two genotypes at three time points (0h, 24 h and 48 h) after spraying SU and IMI herbicides with two replicates. We identified 940 conserved miRNAs and 1515 novel candidate miRNAs in Brassica napus using high-throughput sequencing methods combined with computing analysis. A total of 3284 genes were predicted to be targets of these miRNAs, and their functions were shown using GO, KOG and KEGG annotations. The differentiation expression results of miRNAs showed almost twice as many differentiated miRNAs were found in tolerant genotype M342 (309 miRNAs) after SU herbicide application than in sensitive genotype N131 (164 miRNAs). In additiond 177 and 296 miRNAs defined as differentiated in sensitive genotype and tolerant genotype in response to SU herbicides. The miR398 family was observed to be associated with AHAS herbicide tolerance because their expression increased in the tolerant genotype but decreased in the sensitive genotype. Moreover, 50 novel miRNAs from 39 precursors were predicted. There were 8 conserved miRNAs, 4 novel miRNAs and 3 target genes were validated by quantitative real-time PCR experiment. This study not only provides novel insights into the miRNA content of AHAS herbicides tolerant rapeseed in response to AHAS herbicides, but also demonstrates that miRNAs may be involved in AHAS herbicides tolerance.

In conservation agriculture systems, farmers gain many advantages from retaining crop residue on the soil surface, but crop residue retention in these systems may intervene with the activity of pre-emergence herbicides. A pot study was conducted to evaluate the effect of different rates of pre-emergence herbicides [imazethapyr (100 and 150 g a. i. ha-1), isoxaflutole (100 and 200 g a. i. ha-1), metolachlor (1.5 and 2.25 kg a. i. ha-1), pendimethalin (2.25 and 3.38 kg a. i. ha-1) and prosulfocarb + metolachlor (2.5 and 3.75 kg a. i. ha-1)] on seedling emergence and biomass of Echinochloa colona and Chloris virgata when applied in the presence of sorghum residue at rates equivalent to (0, 3 and 6 t ha-1). When seeds of E. colona and C. virgata were not covered with sorghum residue, the seedling emergence and biomass of both weeds was inhibited by 93-100% and 56-100%, respectively, with the application (both rates) of isoxaflutole, metolachlor, pendimethalin and prosulfocarb + metolachlor. Using sorghum residue resulted in lower herbicide efficacy on both weeds. At 3 t ha-1 sorghum residue, E. colona emergence and biomass reduced by 38-100% and 30-100%, respectively, with application of isoxaflutole, metolachlor and pendimethalin (both rates) in comparison with the no-herbicide treatment. Similarly, the emergence and biomass of C. virgata was also reduced by 92-100% and 25-100%, respectively. The results of this study suggest that crop residue may influence efficacy of commonly used pre-emergence herbicides and that the amount of crop residue on the soil surface should be adjusted according to the nature of the pre-emergence herbicides to achieve adequate weed control.

Glyphosate is a broad-spectrum herbicide that is used worldwide. It represents a potential harm to surface water, and when commercially mixed with surfactants, its uptake is greatly magnified. The most well-known glyphosate-based product is Roundup. This herbicide is potentially an endocrine disruptor and many studies have shown the cytotoxicity potential of glyphosate-based herbicides. In breast cancer (BC) cell lines it has been demonstrated that glyphosate can induce cellular proliferation via estrogen receptors. Therefore, we aimed to identify gene expression changes in ER+ and ER- BC cell lines treated with Roundup and AMPA, to address changes in canonical pathways that would be related or not with the ER pathway, which we believe could interfere with cell proliferation. Using the Human Transcriptome Arrays 2.0, we identified gene expression changes in MCF-7 and MDA-MB-468 exposed to low concentrations and short exposure time to Roundup Original and AMPA. The results showed that at low concentration (0.05% Roundup) and short exposure (48h), both cell lines suffered deregulation of 11 canonical pathways, the most important being cell cycle and DNA damage repair pathways. Enrichment analysis showed similar results, except that MDA-MB-468 altered mainly metabolic processes. In contrast, 48h 10mM AMPA showed fewer differentially expressed genes, but also mainly related with metabolic processes. Our findings suggest that Roundup affects survival due to cell cycle deregulation and metabolism changes that may alter mitochondrial oxygen consumption, increase ROS levels, induce hypoxia, damage DNA repair, cause mutation accumulation and ultimately cell death. To our knowledge, this is the first study to analyze the effects of Roundup and AMPA on gene expression in triple negative BC cells. Therefore, we conclude that both compounds can cause cellular damage at low doses in a relatively short period of time in these two models, mainly affecting cell cycle and DNA repair.

Wheat (Triticum aestivum L) is among the most important cereal crops widely cultivated in the world. Wild oat (Avena fatua L.) competes with wheat for moisture, sunlight, space and nutrition. The successful management of weeds requires sound knowledge of their biology and response to different herbicides. This study inferred the impact of different constant temperature regimes and seed burial depths on seedling emergence and biomass production of wild oat. Moreover, the impact of different post-emergence herbicides applied at different growth stages on biomass production of wild oat was tested. The influence of different wild oat-wheat density (WWD) combinations on biomass production of wheat and wild oat was also inferred. Different constant temperature regimes significantly altered seed germination and biomass production of wild oat. The highest seed germination percentage and biomass production were noted under 15°C and 20°C, whereas the lowest values were recorded under 30°C. Similarly, days to start emergence, seedling emergence percentage and biomass production of wild oat was significantly affected by different seed burial depths. The lowest and the highest values of these parameters were observed under 4 and 10 cm depth, respectively. Different post-emergence herbicides and wild oat growth stages significantly altered biomass production. The highest reduction in fresh and dry biomass was recorded with herbicides' application at 2-4 leaf stage compared with anthesis stage. Clodinofop resulted in higher reduction of fresh biomass, whereas higher reduction in dry biomass was noted with Sulfosulfuron. Seed germination of both species was not affected by different WWD combinations, except for the treatment where no seed was sown of both species. These results indicate that deep burial of seeds could prevent seedling emergence, whereas post-emergence herbicides must be applied at 2-4 leaf stage of wild oat for its effective management.

The herbicides ametryn and clomazone are widely used in sugarcane cultivation, and following microbial degradation are considered as soil and water contaminants. The exposure of microorganisms to pesticides can result in oxidative damage due to an increase in the production of reactive oxygen species (ROS). This study investigated the response of the antioxidant systems of two bacterial strains tolerant to the herbicides ametryn and clomazone. Bacteria were isolated from soil with a long history of ametryn and clomazone application. Comparative analyses based on 16S rRNA gene sequences revealed that strain CC07 is phylogenetically related to Pseudomonas aeruginosa and strain 4C07 to P. fulva. The two bacterial strains were grown for 14 h in the presence of separate and combined herbicides. Lipid peroxidation, reduced glutathione content (GSH) and antioxidant enzymes activities were evaluated. The overall results indicated that strain 4C07 formed an efficient mechanism to maintain the cellular redox balance by producing reactive oxygen species (ROS) and subsequently scavenging ROS in the presence of the herbicides. The growth of bacterium strain 4C07 was inhibited in the presence of clomazone alone, or in combination with ametryn, but increased glutathione reductase (GR) and glutathione S-transferase (GST) activities, and a higher GSH concentration were detected. Meanwhile, reduced superoxide dismutase (SOD), catalase (CAT) and GST activities and a lower concentration of GSH were detected in the bacterium strain CC07, which was able to achieve better growth in the presence of the herbicides. The results suggest that the two bacterial strains tolerate the ametryn and clomazone herbicides with distinctly different responses of the antioxidant systems.

The efficacy of auxinic herbicides, a valuable weed control tool for growers worldwide, has been shown to vary with the time of day in which applications are made. However, little is known about the mechanisms causing this phenomenon. Investigating the differential in planta behavior of these herbicides across different times of application may grant an ability to advise which properties of auxinic herbicides are desirable when applications must be made around the clock. Radiolabeled herbicide experiments demonstrated a likely increase in ATP-binding cassette subfamily B (ABCB)-mediated 2,4-D and dicamba transport in Palmer amaranth (Amaranthus palmeri S. Watson) at simulated dawn compared to mid-day, as dose response models indicated that many orders of magnitude higher concentrations of N-1-naphthylphthalamic acid (NPA) and verapamil, respectively, are required to inhibit translocation by 50% at simulated sunrise compared to mid-day. Gas chromatographic analysis displayed that ethylene evolution in A. palmeri was higher when dicamba was applied during mid-day compared to sunrise. Furthermore, it was found that inhibition of translocation via 2,3,5-triiodobenzoic acid (TIBA) resulted in an increased amount of 2,4-D-induced ethylene evolution at sunrise, and the inhibition of dicamba translocation via NPA reversed the difference in ethylene evolution across time of application. Dawn applications of these herbicides were associated with increased expression of a putative 9-cis-epoxycarotenoid dioxygenase biosynthesis gene NCED1, while there was a notable lack of trends observed across times of day and across herbicides with ACS1, encoding 1-aminocyclopropane-1-carboxylic acid synthase. Overall, this research indicates that translocation is differentially regulated via specific protein-level mechanisms across times of application, and that ethylene release, a chief phytotoxic process involved in the response to auxinic herbicides, is related to translocation. Furthermore, transcriptional regulation of abscisic acid involvement in phytotoxicity and/or translocation are suggested.

Paraquat is one of the most effective herbicides used to control weeds in agricultural management, while the pernicious weed goosegrass (Eleusine indica) has evolved resistance to herbicides, including paraquat. Polyamines provide high-level paraquat resistance in many plants. In the present study, we selected three polyamines, namely, putrescine, spermidine, and spermine, as putative genes to investigate their correlation with paraquat resistance by using paraquat-resistant (R) and paraquat-susceptible (S) goosegrass populations.

Lentil is a poor competitor of weeds and its sensitivity to herbicides is a major hurdle for large scale production. The present study was conducted to select herbicide resistant lentil genotypes through seed mutagenesis. Seeds of three advanced lentil genotypes (LPP 11001, LPP 11100 and LPP 11116) were treated with two different concentrations of ethyl methanesulfonate (EMS; 0.1 and 0.2%), hydrazine hydrate (HH; 0.02 and 0.03%) and sodium azide (SA; 0.01 and 0.02%) to develop M1 seed. The M2 was screened against two herbicides including Ally Max 28.6% SG (X = 34.58 g/ha and 1.5X = 51.87 g/ha) and Atlantis 3.6% WG (X = 395.2 g/ha and 1.5X = 592.8 g/ha) using the following three screening methods: post plant emergence (PPE), pre-plant incorporation (PPI) and seed priming (SP). Data were recorded on survival index and survival percentage from each experimental unit of every population. Plants in all populations were categorized following their reaction to herbicides. The newly developed populations showed greater variation for herbicide resistance when compared to their progenitors. Phenotypic traits were significantly reduced in all the screening environments. Overall, 671 herbicide resistant mutants were selected from all testing environments. The seeds from selected plants were re-mutagenized at 150 Gy of gamma radiation and evaluated against higher dose of herbicides. This allowed selection of 134 herbicide resistant mutants. The selected mutants are useful germplasm for herbicide resistance breeding of lentil.

Herbicides are widely used in agricultural practices for preventing the proliferation of weeds. Upon reaching soil and water, herbicides can harm nontarget organisms, such as bacteria, which need an efficient defense mechanism to tolerate stress induced by herbicides. 2,4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide that exerts increased oxidative stress among bacterial communities. Bacterial isolates were obtained from the biofilm of tanks containing washing water from the packaging of different pesticides, including 2,4-D. The Pseudomonas sp. CMA-7.3 was selected because of its tolerance against 2,4-D toxicity, among several sensitive isolates from the biofilm collection. This study aimed to evaluate the antioxidative response system of the selected strain to 2,4-D. It was analyzed the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase GPX enzymes, that are poorly known in the literature for bacterial systems. The Pseudomonas sp. CMA-7.3 presented an efficient response system in balancing the production of hydrogen peroxide, even at 25x the dose of 2,4-D used in agriculture. The antioxidative system was composed of Fe-SOD enzymes, less common than Mn-SOD in bacteria, and through the activities of KatA and KatB isoforms, working together with APX and GPX, having their activities coordinated possibly by quorum sensing molecules. The peroxide control is poorly documented for bacteria, and this work is unprecedented for Pseudomonas and 2,4-D. Not all bacteria harbor efficient response system to herbicides, therefore they could affect the diversity and functionality of microbiome in contaminated soils, thereby impacting agricultural production, environment sustainability and human health.

Soliva sessilis is a troublesome annual weed species in New Zealand turfgrass. This weed has been controlled selectively in New Zealand turfgrass for many years using pyridine herbicides such as clopyralid. However, in some golf courses, the continuous application of pyridine herbicides has resulted in the selection of S. sessilis populations that are resistant to these herbicides. This study focuses on a clopyralid-resistant population of S. sessilis collected from a golf course with a long history of clopyralid applications. The resistant phenotype of S. sessilis was highly resistant to clopyralid (over 225-fold). It was also cross-resistant to dicamba, MCPA and picloram but not mecoprop. The level of resistance to dicamba was high (7-14-fold) but much lower (2-3-fold) for both MCPA and picloram. The phenotype was morphologically distinct from its susceptible counterpart. Individuals of the clopyralid-resistant phenotype had fewer lobes on their leaves and were slightly larger compared to the susceptible phenotype. Resistant individuals also had a larger leaf area and greater root dry weight than the susceptible plants. An evaluation of internal transcribed spacer (ITS) regions confirmed that clopyralid-resistant phenotypes are conspecific with S. sessilis. In summary, the cross-resistance to several auxinic herbicides in this S. sessilis phenotype greatly reduces chemical options for controlling it; thus, other integrated management practices may be needed such as using turfgrass competition to reduce weed germination. However, the morphological differences between resistant and susceptible plants make it easy to see, which will help with its management.

We estimated the risk of selecting for herbicide resistance in 101 weed species known to occur in wheat and barley crops on farms in New Zealand. A protocol was used that accounts for both the risk that different herbicides will select for resistance and each weed's propensity to develop herbicide resistance based on the number of cases worldwide. To provide context we documented current herbicide use patterns. Most weeds (55) were low-risk, 30 were medium-risk and 16 high-risk. The top ten scored weeds were Echinochloa crus-galli, Poa annua, Lolium multiflorum, Erigeron sumatrensis, Raphanus raphanistrum, Lolium perenne, Erigeron bonariensis, Avena fatua, Avena sterilis and Digitaria sanguinalis. Seven out of ten high-risk weeds were grasses. The most used herbicides were synthetic auxins, an enolpyruvylshikimate-phosphate synthase inhibitor, acetolactate synthase (ALS) inhibitors, carotenoid biosynthesis inhibitors, and long-chain fatty acid inhibitors. ALS-inhibitors were assessed as posing the greatest risk for more species than other modes-of-action. Despite pre-emergence herbicides being known to delay resistance, New Zealand farmers only applied flufenacet and terbuthlazine with high frequency. Based on our analysis, surveys for herbicide-resistant species should focus on the high-risk species we identified. Farmer extension efforts in New Zealand should address resistance evolution in cropping weeds.

Chlorimuron-ethyl and atrazine are two herbicides with long half-lives in soil; their long-term and excessive application has led to a series of environmental problems. In this study, the strains Chenggangzhangella methanolivorans CHL1 and Arthrobacter sp. ART1 were combined and used for the remediation of chlorimuron-ethyl, atrazine and combined contaminated soils in a microcosm experiment. Changes in chlorimuron-ethyl and atrazine concentrations in soils were monitored, and variations in the soil microbial community were studied by phospholipid fatty acid (PLFA) analysis. The two inoculated degrading strains accelerated the degradation of chlorimuron-ethyl and atrazine in soil, especially in the combined contaminated soil. Addition of the two herbicides and their combination generally decreased the concentrations of total PLFAs, total bacterial PLFAs, Gram-negative and Gram-positive bacterial PLFAs and Shannon-Wiener indices, and changed microbial community composition, whilst stimulating fungal PLFA concentrations. In addition, the combined herbicide treatment had more impact on microbial biomass than the single herbicide treatments. Inoculation treatments significantly relieved the effects of herbicides on soil microbial biomass, diversity and community structure. This study demonstrated that strains CHL1 and ATR1 have the potential to remediate chlorimuron-ethyl, atrazine and combined contaminated soils, and provided valuable information for remediation of chlorimuron-ethyl, atrazine and combined contaminated soils in situ.

No-tillage with stubble retention is a widely used cropping system for its conservation and yield benefits. The no-tillage farming system in southern Australia relies heavily on herbicides for weed management, but heavy crop residues may have a negative impact on the activity of pre-emergent herbicides applied. Any herbicide intercepted by the crop residue may not reach the soil surface without timely rainfall and may dissipate due to volatilisation, photo-degradation and/or microbial activity. Two experiments were carried out to investigate the interception of prosulfocarb, pyroxasulfone, and trifluralin herbicides by wheat residue and retention following simulated rainfall. For the first experiment, there were four simulated rainfall amounts (0, 5, 10, and 20 mm), three intensities (5, 10, and 20 mm h-1) and five application times (immediately after spraying herbicide, 6 h, 1, 7, and 14 days after spraying). In the second experiment, 20 mm of rainfall was applied at 10 mm h-1 in either 4 × 5 mm rainfall events over two days, 2 × 10 mm rainfall events over one day, or a single 20 mm rainfall event, with a no-rainfall control treatment. Bioassays were used to assess the herbicide activity/availability in the soil and remaining on the residue, using cucumber (Cucumis sativus L.) and Italian ryegrass (Lolium multiflorum Lam.) as indicator plants. At higher rainfall amounts, most of the herbicide leached from the stubble into the soil soon after application; more so with rain in one event rather than multiple events. However, the intensity of rainfall had no effect. Pyroxasulfone leached easily from the residue to the soil to potentially offer good weed control, prosulfocarb had an intermediary leaching effect, while only a small amount of trifluralin leached from stubble after rain. Therefore, in no-tillage situations with large amounts of crop residue present on the soil surface, herbicides that leach easily from the residue should be considered, like pyroxasulfone.

Weed infestation is a persistent problem for centuries and continues to be major yield reducing issue in modern agriculture. Chemical weed control through herbicides results in numerous ecological, environmental, and health-related issues. Moreover, numerous herbicides have evolved resistance against available herbicides. Plant extracts are regarded as an alternative to herbicides and a good weed management option. The use of plant extracts is environmentally safe and could solve the problem of herbicide resistance. Therefore, laboratory and wire house experiments were conducted to evaluate the phytotoxic potential of three Fabaceae species, i.e., Cassia occidentalis L. (Coffee senna), Sesbania sesban (L.) Merr. (Common sesban) and Melilotus alba Medik. (White sweetclover) against seed germination and seedling growth of some broadleaved weed species. Firstly, N-hexane and aqueous extracts of these species were assessed for their phytotoxic effect against lettuce (Lactuca sativa L.). The extracts found more potent were further tested against germination and seedling growth of four broadleaved weed species, i.e., Parthenium hysterophorus L. (Santa-Maria), Trianthema portulacastrum L. (Pigweed), Melilotus indica L (Indian sweetclover). and Rumex dentatus L. (Toothed dock) in Petri dish and pot experiments. Aqueous extracts of all species were more toxic than their N-hexane forms for seed germination and seedling growth of lettuce; therefore, aqueous extracts were assessed for their phytotoxic potential against four broadleaved weed species. Aqueous extracts of all species proved phytotoxic against T. portulacastrum, P. hysterophorus, M. indica and R. dentatus and retarder their germination by 57, 90, 100 and 58%, respectively. Nevertheless, foliar spray of C. occidentalis extract was the most effective against T. portulacastrum as it reduced its dry biomass by 72%, while M. alba was effective against P. hysterophorus, R. dentatus and M. indica and reduced their dry biomass by 55, 68 and 81%, respectively. It is concluded that aqueous extracts of M. alba, S. sesban and C. occidentalis could be used to retard seed germination of T. portulacastrum, P. hysterophorus, M. indica and R. dentatus. Similarly, aqueous extracts of C. occidentalis can be used to suppress dry biomass of T. portulacastrum, and those of M. alba against P. hysterophorus, R. dentatus. However, use of these extracts needs their thorough testing under field conditions.

The annual suicide rate in South Korea is the highest among the developed countries. Paraquat is a highly lethal herbicide, commonly used in South Korea as a means for suicide. We have studied the effect of the 2011 paraquat prohibition on the national suicide rate and method of suicide in South Korea. We obtained the monthly suicide rate from 2005 to 2013 in South Korea. In our analyses, we adjusted for the effects of celebrity suicides, and economic, meteorological, and seasonal factors on suicide rate. We employed change point analysis to determine the effect of paraquat prohibition on suicide rate over time, and the results were verified by structural change analysis, an alternative statistical method. After the paraquat prohibition period in South Korea, there was a significant reduction in the total suicide rate and suicide rate by poisoning with herbicides or fungicides in all age groups and in both genders. The estimated suicide rates during this period decreased by 10.0% and 46.1% for total suicides and suicides by poisoning of herbicides or fungicides, respectively. In addition, method substitution effect of paraquat prohibition was found in suicide by poisoning by carbon monoxide, which did not exceed the reduction in the suicide rate of poisoning with herbicides or fungicides. In South Korea, paraquat prohibition led to a lower rate of suicide by paraquat poisoning, as well as a reduction in the overall suicide rate. Paraquat prohibition should be considered as a national suicide prevention strategy in developing and developed countries alongside careful observation for method substitution effects.