Glyphosate Application Research Articles

Quizalofop-resistant rice response to quizalofop when exposed to low rates of glyphosate and imazethapyr

AbstractInjury to quizalofop-resistant rice was reported in some fields following postemergence applications of quizalofop. Glyphosate-resistant (GR) corn, cotton, and soybean, and imidazolinone-resistant rice are grown near quizalofop-resistant rice. Herbicide drift from glyphosate and imazethapyr and the resulting crop injury and potential yield loss is a cause of concern for producers. Field experiments conducted near Colt, and Keiser, AR, in 2021 evaluated whether low rates of glyphosate or imazethapyr interact with sequential quizalofop applications to exacerbate injury to quizalofop-resistant rice compared to quizalofop applications alone. Herbicide treatments consisted of a low rate of glyphosate (90 g ae ha−1) or imazethapyr (10.7 g ai ha−1) applied 10, 7, 4, and 0 d before the 2-leaf growth stage of rice, and glyphosate or imazethapyr, at the same rate and timings, followed by quizalofop at 120 g ai ha−1 applied to 2-leaf rice. All plots treated with quizalofop received a subsequent application of the same herbicide and rate at the 5-leaf rice stage. At 28 d after final treatment (DAFT), glyphosate followed by quizalofop the same day to 2-leaf rice caused 77% injury compared with 58% when glyphosate was applied alone, regardless of location. Glyphosate followed by quizalofop the same day reduced rough rice grain yield by 67% compared with 33% when glyphosate was applied alone to 2-leaf rice at the Colt location. Application of imazethapyr followed by quizalofop the same day to 2-leaf rice caused more injury (63% and 19% injury at the Colt and Keiser locations, respectively) than imazethapyr alone (42% and 7% injury at the Colt and Keiser locations, respectively) at 35 DAFT. Overall, glyphosate and imazethapyr followed by quizalofop applications worsened injury compared to glyphosate, imazethapyr, and quizalofop applications alone. As the interval between exposure to a low rate of glyphosate or imazethapyr and quizalofop decreases, the detrimental effect of herbicide on rice likewise increases.

Urinary biomonitoring of glyphosate exposure among male farmers and non-farmers in the Biomarkers of Exposure and Effect in Agriculture (BEEA) study

BACKGROUND AND AIM: Glyphosate is the most widely applied herbicide worldwide. Despite potential health effects of glyphosate, biomonitoring data of glyphosate exposure in agriculture and other settings are limited. We measured urinary glyphosate concentrations and assessed their determinants among male farmers and non-farmers from Iowa and North Carolina in the BEEA study. METHODS: Based on questionnaire-assessed pesticide exposure histories, we selected four groups of BEEA participants: recently exposed farmers with occupational glyphosate use in the last 7 days (n=98), farmers with high cumulative lifetime days of glyphosate use (>80th percentile) but no use in the last 7 days (n=70), farmers with minimal lifetime glyphosate use (n=100), and non-farmers with no occupational pesticide exposure (n=100). We quantified glyphosate in first-morning void urine samples using ion chromatography isotope-dilution tandem mass spectrometry. We estimated geometric mean urinary glyphosate concentrations across groups and evaluated associations with potential determinants using linear regression. RESULTS: Glyphosate was detected in urine of most recently (91%), high-lifetime (93%), and low-lifetime (88%) exposed farmers, as well as non-farmers (81%); geometric mean concentrations were 0.86, 0.58, 0.44, and 0.37 µg/L, respectively. Compared to non-farmers, urinary glyphosate concentrations were significantly elevated among recently exposed farmers (P<0.0001), particularly those who used glyphosate within 1 day of urine collection [age- and creatinine-adjusted geometric mean ratio (GMR)=6.4, 95% confidence interval (CI)=4.3-9.3] and those not wearing gloves during glyphosate application (GMR=2.6, 95% CI=2.0-3.4). CONCLUSIONS: Preliminary results suggest that a high proportion of both farming and non-farming populations may be exposed to glyphosate. Substantial exposure contrast between those with and without recent occupational glyphosate use was detectable in urine. Given the short elimination half-life of glyphosate, the exposure differences between groups may be even greater than those reflected by measured urine concentrations. Continued biomonitoring of glyphosate in various settings is warranted. KEYWORDS: Glyphosate, exposure assessment, pesticide biomonitoring

Glyphosate excessive use chronically disrupts the shikimate pathway and can affect photosynthesis and yield in citrus trees

Glyphosate excessive use is reported in Brazilian citrus orchards, whereas there is speculation about its consequences and the published studies are contradictory and inconclusive. This study aimed to describe the possible harmful effects by simulating glyphosate drift directly to the leaves of ∼4-yr-old citrus plants. As major results, glyphosate doses >360 g ae ha−1 increased the shikimate accumulation in leaves (up to 2.3-times above control), which was increased after a second glyphosate application (up to 3.5-times above control), even after a 240-d interval. Interestingly, shikimate accumulation was occasionally related to a dose-response of the herbicide at specific times; however, the doses had their accumulation peak on determined dates. These accumulations were directly correlated to reduced net photosynthesis even months after the glyphosate sprays. Quantum productivity based on electron transport through the photosystem II and apparent electron transport reductions up to 17% were also observed during the entire experiment course. Similarly, quantum productivity based on CO2 assimilation of glyphosate sprayed leaves decreased up to four times compared to the control after the second application. Glyphosate doses >360 g ae ha−1 increased stomatal conductance and transpiration as the carboxylation efficiency decreased, evidencing a carbon drainage in the Calvin-Benson cycle. These metabolic and physiological disturbances suggest possible photooxidative damage and an increase in photorespiration, which may be a mitigation strategy by the citrus plants to glyphosate effects, by the cost of reducing the citrus fruit yield (up to 57%). It is concluded that glyphosate phytotoxicity damages citrus plants over time due to chronic disturbances in the shikimate pathway and photosynthesis, even when there are no symptoms. This study is the first report to demonstrate how glyphosate damages citrus trees beyond the shikimate pathway.

Alleviation of Herbicide Toxicity in Solanum lycopersicum L.-An Antioxidant Stimulation Approach.

Application of the herbicide glyphosate in crops is a common practice among farmers around the world. Tomato is one of the crops that are treated with glyphosate to fight weed growth and loss of crop. However, tomato plants often show phytotoxic effects from glyphosate. In this study, the ability of pongamia oil derived from Pongamia pinnata (known also as Millettia pinnata) tree to alleviate the herbicide glyphosate toxicity effects in tomato (S. lycopersicum L. cv. Micro-tom) plants was tested. Tomato plants were treated with a mixture of a dose of (GLY) glyphosate (10 mg kg−1) and different doses of pongamia oil (PO) foliar spray (5, 10, 50, and 100 mM) and compared with the herbicide or oil control (glyphosate 10 mg kg−1 or pongamia oil PO 50 mM). Some morphological features, non-enzymatic and enzymatic antioxidants, and gene expression were observed. Glyphosate-treated plants sprayed with PO 50 mM (GLY + PO 50) showed increased root biomass (0.28 g-p ≤ 0.001), shoot biomass (1.2 g-p ≤ 0.01), H2O2 (68 nmol/g), and the activities of superoxide dismutase (SOD; 40 mg-p ≤ 0.001), catalase (CAT; 81.21 mg-p ≤ 0.05), ascorbate peroxidase (APX; 80 mg-p ≤ 0.01) and glutathione reductase (GR; 53 min/mg-F4,20 = 15.88, p ≤ 0.05). In contrast, these plants showed reduced contents of Malondialdehyde (MDA; 30 nmol/g-F4,20 = 18.55, p ≤ 0.01), O2 (0.6 Abs/g), Prolne (Pro; 345 µg/g), Glutathine (GSH; 341 nmol/mg-p ≤ 0.001), ascorbate (AsA; 1.8 µmol/gm), ascorbic acid (AA; 1.62 mg-p ≤ 0.05) and dehydroascorbate (DHAR; 0.32 mg p ≤ 0.05). The gene expression analysis was conducted for seven oxidative stress related genes besides the house-keeping gene Actin as a reference. The gene CYP1A1450 showed the highest mRNA expression level (6.8 fold ± 0.4) in GLY-treated tomato plants, whereas GLY-treated plants + PO 50 showed 2.9 fold. The study concluded that foliar spray of 50 mM pongamia oil alleviated the toxic effects of glyphosate on tomato plants in the form of increased root and shoot biomass, SOD, CAT, APX, and GR activity, while reduced MDA, O2, Pro, GSH, AsA, AA, DHAR, and gene CYP1A1450 expression.

Glyphosate Application and Potential Eleusine Indica Resistance in Oil Palm Plantations

Eleusine indica is a grass weed in oil palm plantations, especially during the period of immature crops. The application of glyphosate for weed control shows diverse effectiveness. This study aims to determine the age of susceptible weeds in increasing the effectiveness of glyphosate in controlling E. indica. The study tested the application of glyphosate with three levels (486, 729, and 972 g/ha) at three different weed ages (3, 6, and 9 weeks). E. indica was taken from oil palm plantations that were previously glyphosate-depleted, then sprayed with glyphosate according to the dose studied. Each treatment combination is represented by five pots containing five individual weeds. The results showed that the application of glyphosate aged three and six weeks of higher effectiveness controlled E. indica for doses of 486 and 729 g/ha) than a nine-week application for all doses tested. Regrowth of weeds is found mainly the application of glyphosate at the age of a month of weeks. The development of E. indica's resistance to glyphosate needs attention in oil palm plantations.

Targeted timing of hairy vetch cover crop termination with roller crimper can eliminate glyphosate requirements in no-till sunflower

No-till cropping systems with cover crops can improve soil health, but often rely on glyphosate, which is a contentious herbicide. In this study, we investigated whether a system based on the direct sowing of sunflower (Helianthus annuus) in the dead mulch of a roller-crimped hairy vetch (Vicia villosa) could be competitive with a system where glyphosate is also sprayed to terminate the cover crop and to control weeds. We hypothesized that optimum timing of roller-crimping would be key to eliminate glyphosate requirements while maintaining sunflower performance. In a 3-year on-farm experiment, we compared three vetch termination stages (early: pre-flowering; Intermediate: beginning of flowering; late: 70% flowering) and three glyphosate rates (Nil, half and full, i.e. 1440 g of active ingredient per hectare). Vetch biomass increased progressively from early to late termination stages, and ranged between 414 and 658 g m−2. Higher vetch biomass was correlated with lower weed biomass. Treatments had inconsistent effects on weed diversity and composition, largely determined by the interactions between treatments and seasonal (different years) or local factors (different fields). Glyphosate-based treatments seemed to select for aggressive weed species, but no clear species filtering effect based on ecological or functional traits was detected. Shannon H’ was positively correlated with sunflower grain yield below a weed dry biomass threshold of 150 g m−2. Crop yield with early termination stage was a failure without glyphosate application. However, crop yield with late vetch termination was acceptable, being at par or 15% higher (mean of first and second years) in no-glyphosate compared with glyphosate-based treatments. Crop gross margins showed the same trend (+33% for no-glyphosate compared with glyphosate-based treatments). This study, for the first time, shows that targeted timing of roller-crimped hairy vetch in no-till sunflower can result in equal agronomic and economic performances as addition of glyphosate.

Effect of Water Deficit on Growth and Photoassimilate Partitioning in Leersia hexandra and Luziola peruviana

Minimum tillage in rice production is increasing in southern Brazil, reaching 60% of the total planted area. Compared to conventional tillage, in this system there is an increase in the occurrence of perennial weeds, such as Luziola peruviana and Leersia hexandra, which are amphibious plants, as they can occur in both flooded environments and aerobic conditions. These weeds are controlled in burn-down before rice planting by glyphosate applications, the efficacy of which depends on the soil moisture. This study aimed to evaluate the effect of different soil moisture regimes in L. hexandra and L. peruviana growth and photoassimilate partitioning. Both species were assessed under soil moisture regimes of flooded, saturated, 7 kPa, 15 kPa, 40 kPa, and 100 kPa (experiment 1) and flooded, saturated, and 7 kPa (experiment 2). Plants were sampled immediately after drainage (3 months after transplant) and 1 and 2 weeks after drainage. The results showed that as soil moisture levels decreased, growth and development parameters were negatively affected in both species. Photoassimilate partitioning was affected by water regime and differences were observed between species. The total soluble sugars and starch content decreased in the leaves, and sucrose concentration increased in the roots following drainage. Soil drainage affects the growth and alters carbohydrate partitioning of these weeds, increasing the sugar storage in roots. The agronomic impact of these findings is that this behavior may affect herbicide transport in phloem and may affect herbicide efficacy.

Modeling the impact of winter cover crop on tile drainage and nitrate loss using DSSAT model

Increasing demand for food has amplified the use of fertilizer. Intensive agriculture practices in the Upper Mississippi basin have been linked to the formation of a hypoxic zone in the Gulf of Mexico. Previous studies have recommended the use of winter cover crop in the maize-soybean rotation as an eco-efficient solution in reducing the nitrate-nitrogen (NO3-N) loss via a sub-surface drainage system. Therefore, the objective of this study is to evaluate the impact of cereal rye as a winter cover crop in the maize-soybean system on reducing nutrient loss via tile drainage using the DSSAT model. The experiments include four treatments with a combination of two different nitrogen (N) application timing with cover crop (CC) and without cover crop (NCC): fall-applied N without cover crop (FN), spring-applied N without cover crop (SN), fall-applied N with cover crop (FCC), and spring-applied N with cover crop (SCC). The calibrated DSSAT model was utilized to assess the impact of the cover crop by comparing NO3-N losses and cash crop yields between CC and NCC treatments for different N fertilization timings. The model calibrated for cereal rye biomass in the FCC treatment estimated the observed cereal rye growth for SCC treatment considerably well (R2 >0.91). The model successfully predicted the impact of cereal rye on nitrate loss and tile drainage with 43.6% and 45.4% (48.6% and 47.8% observed) nitrate loss reduction and 21.3% and 21.0% (30.2% and 19.4% observed) tile drainage volume reduction in fall and spring N application treatments, respectively. The results from this research suggest that DSSAT can predict the cereal rye growth and assess the soil water-nutrient dynamics in both CC and NCC systems. However, the model was not able to replicate the impact of cereal rye on the cash crop yields due to the higher N mineralization simulated in the CC compared to the NCC treatments. This could be due to the use of glyphosate to terminate the cereal rye and the presence of tillage radish along with the cereal rye. The glyphosate application hastens the decomposition process; however, it also reduces the overall residue. The chemical termination and intercropping feature are not available in the DSSAT model currently. The cereal rye hosted pathogens and pests might also be responsible for lowering maize yield in the observations.

Effects of Glyphosate Application on Preharvest Fruit Drop and Yield in ‘Valencia’ Citrus

The use of glyphosate as a post-emergent weed management tool is crucial in Florida citrus production. However, extensive and nonjudicious application of glyphosate has drawn increasing concerns about its inadvertent effects on citrus, mainly linked to its possible impacts on preharvest fruit drop. Our study investigated the effect of applying glyphosate in the tree rows near the fruit harvesting window on fruit drop and yield in ‘Valencia’ sweet orange. Field trials were conducted at Southwest Florida Research and Education Center, Immokalee, FL. The experiments had a randomized complete block design with four replications. Three different doses of glyphosate within the labeled range of rates in citrus (i.e., low, medium, and high at 0.84, 2.10, and 4.20 kg acid equivalents of glyphosate per hectare, respectively) along with a water control treatment were sprayed in ‘Valencia’ citrus tree rows close to the harvesting period and assessed for their effects on preharvest fruit drop and yield. Our findings show that glyphosate application near the harvesting window may influence the fruit detachment force (FDF) in Valencia citrus; however, no significant effect on increasing fruit drop or reducing yield was observed during this 2-year study.

Effect of cotton herbicide programs on weed population trajectories and frequency of glyphosate-resistant Palmer amaranth (Amaranthus palmeri)

AbstractThe adoption of dicamba-resistant cotton (Gossypium hirsutum L.) cultivars allows using dicamba to reduce weed populations across growing seasons. However, the overuse of this tool risks selecting new herbicide-resistant biotypes. The objectives of this research were to determine the population trajectories of several weed species and track the frequency of glyphosate-resistant (GR) Palmer amaranth (Amaranthus palmeri S. Watson) over 8 yr in dicamba-resistant cotton. An experiment was established in North Carolina in 2011, and during the first 4 yr, different herbicide programs were applied. These programs included postemergence applications of glyphosate, alone or with dicamba, with or without residual herbicides. During the last 4 yr, all programs received glyphosate plus dicamba. Biennial rotations of postemergence applications of glyphosate only and glyphosate plus dicamba postemergence with and without preemergence herbicides were also included. Sequential applications of glyphosate plus dicamba were applied to the entire test area for the final 4 yr of the study. No herbicide program was entirely successful in controlling the weed community. Weed population trajectories were different according to species and herbicide program, creating all possible outcomes; some increased, others decreased, and others remained stable. Density of resistant A. palmeri increased during the first 4 yr with glyphosate-only programs (up to 11,739 plants m−2) and decreased a 96% during the final 4 yr, when glyphosate plus dicamba was implemented. This species had a strong influence on population levels of other weed species in the community. Goosegrass [Eleusine indica (L.) Gaertn.] was not affected by A. palmeri population levels and even increased its density in some herbicide programs, indicating that not only herbicide resistance but also reproductive rates and competitive dynamics are critical for determining weed population trajectories under intensive herbicide-based control programs. Frequency of glyphosate resistance reached a maximum of 62% after 4 yr, and those levels were maintained until the end of the experiment.

Glyphosate infiltrates the brain and increases pro-inflammatory cytokine TNFα: implications for neurodegenerative disorders

BackgroundHerbicides are environmental contaminants that have gained much attention due to the potential hazards they pose to human health. Glyphosate, the active ingredient in many commercial herbicides, is the most heavily applied herbicide worldwide. The recent rise in glyphosate application to corn and soy crops correlates positively with increased death rates due to Alzheimer’s disease and other neurodegenerative disorders. Glyphosate has been shown to cross the blood–brain barrier in in vitro models, but has yet to be verified in vivo. Additionally, reports have shown that glyphosate exposure increases pro-inflammatory cytokines in blood plasma, particularly TNFα.MethodsHere, we examined whether glyphosate infiltrates the brain and elevates TNFα levels in 4-month-old C57BL/6J mice. Mice received either 125, 250, or 500 mg/kg/day of glyphosate, or a vehicle via oral gavage for 14 days. Urine, plasma, and brain samples were collected on the final day of dosing for analysis via UPLC–MS and ELISAs. Primary cortical neurons were derived from amyloidogenic APP/PS1 pups to evaluate in vitro changes in Aβ40-42 burden and cytotoxicity. RNA sequencing was performed on C57BL/6J brain samples to determine changes in the transcriptome.ResultsOur analysis revealed that glyphosate infiltrated the brain in a dose-dependent manner and upregulated TNFα in both plasma and brain tissue post-exposure. Notably, glyphosate measures correlated positively with TNFα levels. Glyphosate exposure in APP/PS1 primary cortical neurons increases levels of soluble Aβ40-42 and cytotoxicity. RNAseq revealed over 200 differentially expressed genes in a dose-dependent manner and cell-type-specific deconvolution analysis showed enrichment of key biological processes in oligodendrocytes including myelination, axon ensheathment, glial cell development, and oligodendrocyte development.ConclusionsCollectively, these results show for the first time that glyphosate infiltrates the brain, elevates both the expression of TNFα and soluble Aβ, and disrupts the transcriptome in a dose-dependent manner, suggesting that exposure to this herbicide may have detrimental outcomes regarding the health of the general population.

Comparing field-based management approaches for invasive Winter Heliotrope (Petasites pyrenaicus, Asteraceae)

Winter Heliotrope (Petasites pyrenaicus, previously P. fragrans), is a persistent, rhizome-forming species found throughout the Mediterranean region and North Africa and is an Invasive Alien Plant (IAP) in the UK and Ireland. P. pyrenaicus excludes native flora by forming a dense, compact canopy that persists for much of the growing season, and is often found growing in rough ground, riparian areas and along communication routes, incurring significant management costs at sites of conservation interest. Our study describes the first field-based assessment of P. pyrenaicus control treatments, testing 12 physical and/or chemical treatments in replicated 1 m2 plots over four years and one chemical treatment over three years. Treatments focused on understanding phenology and resource allocation to exploit rhizome source-sink relationships in P. pyrenaicus. Multiple-stage glyphosate- and picloram-based treatments reduced leaf canopy cover to zero (%) over time, though no treatment completely eradicated P. pyrenaicus. When designing management strategies, effective P. pyrenaicus control may be achieved by a single annual soil and/or foliar application of picloram at 1.34 kg AE ha-1 in spring, or by a single annual foliar application of glyphosate in spring at 2.16 kg AE ha-1. Control is not improved by the addition of other herbicides or physical treatment methods, underlining the importance of these herbicides for perennial invasive plant management. This work confirms the importance of considering plant phenology, resource allocation and rhizome source-sink relationships, to increase treatment efficacy and reduce the environmental impacts associated with the management of P. pyrenaicus and other invasive, rhizome forming species.

Effects of exposure to glyphosate on oxidative stress, inflammation, and lung function in maize farmers, Northern Thailand

BackgroundGlyphosate is a herbicide which is commonly used in agricultural areas. However, previous studies on glyphosate exposure in farmers and their health are still scarce.MethodsA longitudinal pre-post study was performed among maize farmers. Information from questionnaires, urine and blood samples, and lung function were collected a day before and a day after glyphosate application in the morning. The urine samples were analyzed using liquid chromatography-tandem mass spectrometry to detect glyphosate levels. Serum samples were analyzed to detect malondialdehyde (MDA), glutathione (GHS), and C-reactive protein (CRP) levels using thiobarbituric acid, dithiobisnitrobenzoic acid, and nephelometry, respectively. Lung function performances were measured using a spirometer.ResultsA total of 180 maize farmers met the study inclusion criteria. After glyphosate application, it was found that increased urinary glyphosate levels contributed to increased serum MDA (β = 0.024, 95% CI = 0.000, 0.0047) and decreased serum GHS (β = -0.022, 95% CI = -0.037, -0.007), FEV1 (β = -0.134, 95% CI = -0.168, -0.100), FEV1/FVC (β = -0.062, 95% CI = -0.082, -0.042) and PEF (β = -0.952, 95% CI = -1.169, -0.735).ConclusionsExposure to glyphosate during glyphosate application had significant effects on oxidative stress and lung function in maize farmers.

Evaluations of alternative herbicides to glyphosate for wilding pine control during forestry site preparation in the southeastern United States

AbstractControl of southern pine species that easily establish from seed, such as loblolly pine and slash pine (wilding pines), has historically been achieved economically through the use of prescribed fire or application of glyphosate or glyphosate and saflufenacil during site preparation. Currently, alternatives to glyphosate are being investigated for wilding pine control because of health and safety concerns over glyphosate reported by some organizations. Two exploratory studies in the Coastal Plain Region of Georgia investigated the potential of several herbicides for wilding pine control with 0.56 to 0.70 kg ha−1 of 0.9-kg ae imazapyr included in all herbicide treatments. Application timings for Study 1 were July and September (n = 8 treatments per timing), whereas Study 2 took place in July and early November (n = 4 treatments per timing). In Study 1, various rates of choline triclopyr, ester triclopyr, fluroxypyr, aminopyralid + florpyrauxifen-benzyl, and aminopyralid + triclopyr were tested, while two treatments contained glyphosate. Study 2 investigated mixtures containing flumioxazin, glufosinate, and triclopyr. Results for Study 1 revealed that the two treatments containing glyphosate had the greatest percent loblolly pine control after 120 d (87.5% and 88.6% control, respectively), while the next best control was offered by a treatment containing imazapyr plus 3.36 kg ha−1 choline triclopyr (52.6% control). July treatments offered better control than September treatments, but the efficacy of September treatments may have been impacted by a severe drought. In Study 2, treatments applied during early November that contained imazapyr and glufosinate or imazapyr, glufosinate, and flumioxazin resulted in 100% control of mixed loblolly and slash pine seedlings and saplings. All November treatments offered better control than July treatments in Study 2. Promising results from Study 2 suggest that glufosinate may warrant additional study for use in forestry site preparation as an alternative to glyphosate to control wilding pines.

Post-harvesting glyphosate and imazapyr application on Eucalyptus stumps to control coppice

ABSTRACT The objective of this research was to assess the efficiency of applying glyphosate and imazapyr to Eucalyptus cut-stump surfaces after harvesting to control sprouting. Two experiments were conducted in Eucalyptus grandis × Eucalyptus urophylla plantations arranged in a randomised block design with five treatments and five replicates. In experiment 1, 0, 0.84, 1.67, 2.50 and 3.34 kg of acid equivalent (a.e.) ha−1 of glyphosate was applied. Experiment 2 involved the application of 0, 0.028, 0.083, 0.140 and 0.195 kg a.e. ha−1 of imazapyr. The application was carried out between 42 and 48 hours after harvesting in replicates of 36 stumps. Increased glyphosate doses increased coppice control to more than 90%. Coppice was present on approximately 30% of the stumps treated with the highest glyphosate dose. However, these shoots showed low vigour 225 days after application, with mean values of about 0.30 m in height and 0.5 shoots per stump. In the control treatment, coppice reached 3.0 m in height and 8.0 kg green mass weight, and coppice was present on 97% of the stumps. The highest imazapyr doses increased shoot control to 80%. Post-harvesting application to cut stumps reduced coppice development. However, only the glyphosate doses of 2.50 and 3.34 kg a.e. ha−1 presented satisfactory coppice control levels without follow-up operations.

EFFECTS OF SUPPRESSION APPLICATIONS ON SUMMER ASPHODEL (Asphodelus aestivus Brot.) DENSITY, BOTANICAL COMPOSITION, FORAGE YIELD AND QUALITY OF AEGEAN RANGELANDS

Summer asphodel (Asphodelus aestivus Brot.) has an underground storage organ that enables the plant tosurvive extreme conditions and contains alkaloids that are toxic to the livestock in rangelands. For this reason,the experiment was carried out in the rangeland of Aydin province (Turkey) in order to determine the mosteffective methods of weed management where there is an increase in the summer asphodel (Asphodelus aestivusBrot.) population. In the study, the effects of 8 different control methods (control, mowing, fertilization,paraquat, glyphosate, 2,4-D, 2,4-D + Picloram, grubbing) on yield, quality and botanical composition wereinvestigated. Result of the findings in this study shows that the grasses increased more in vegetation. The highestvalues of hay yield were observed in paraquat and fertilization applications. High values of crude protein yieldwere found in fertilization and grubbing applications. The lowest population of summer asphodel (Asphodelusaestivus Brot.) was obtained grubbing and paraquat applications. Together with these results, grubbing,fertilization, paraquat and glyphosate applications come to the fore. However, due to the high workforce, it issignificant to choose an application considering the size of the rangeland and the population of the indicatorweed species.

Phytotonic effects of thiamethoxam on sugarcane managed with glyphosate as a ripener.

Thiamethoxam and glyphosate are widely used in sugarcane production as an insecticide and ripener, respectively. In this study, the potential of these chemical products to also elicit phytotonic effects and enhance the physiological development and yield of sugarcane was evaluated. In field experiments, thiamethoxam and glyphosate were applied to sugarcane individually or in combination, and the effects of these chemical management strategies on sugarcane biometric and technological parameters were assessed. Thiamethoxam application improved biometric parameters, especially stalk yield. Glyphosate application increased sugar yield, despite reducing the number of stalks and consequently the stalk yield. Application of the insecticide thiamethoxam to sugarcane attenuates the depreciative effect of ripener (glyphosate) and has a potential phytotonic effect by increasing sugar yields in the early and late seasons. © 2022 Society of Chemical Industry.

Detection and accumulation of environmentally-relevant glyphosate concentrations delivered via pulse- or continuous-delivery on passive samplers

Glyphosate is the most commonly used herbicide globally, which has contributed to its ubiquitous presence in the environment. Glyphosate application rates and delivery to surface water vary with land use. Streams in urban and agricultural catchments can experience continuous delivery of low concentrations of glyphosate and aminomethylphosphonic acid (AMPA), while their presence in forest streams occurs as an episodic pulse following silvicultural application. We assessed whether trace concentrations of glyphosate delivered as a 1-day pulse (mimic silvicultural applications) followed by flushing with deionized water would affect the detection of glyphosate or AMPA on novel passive samplers, Polar Organic Chemical Integrative Sampler with Molecular Imprinted Polymer (POCIS-MIP), compared with continuous delivery (mimic agricultural or urban applications). Within each delivery type, POCIS-MIP were exposed to seven treatment concentrations of Rodeo (equivalent to 0.0 to 1.84 μg glyphosate L−1). Experimental results demonstrate POCIS-MIP can detect differences in relative glyphosate concentrations above 0.115 μg L−1 (pulse-delivery) or 0.23 μg L−1 (continuous-delivery), but were unable to distinguish trace concentrations (i.e., < 0.115 or 0.23 μg L−1). Our results suggest POCIS-MIP may better retain glyphosate when delivered as a pulse than when delivered continuously, but both underestimated actual treatment concentrations by 46 to 56%. There is a need to demonstrate the field applicability of passive sampling methods to improve environmental monitoring of silvicultural herbicides, and our results demonstrate passive samplers were unable to distinguish lower concentrations, suggesting a limited utility for determining trace concentration levels such as those experienced during or immediately after silvicultural application.

Reducing MCPA herbicide pollution at catchment scale using an agri-environmental scheme

In river catchments used as drinking water sources, high pesticide concentrations in abstracted waters require an expensive treatment step prior to supply. The acid herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) is particularly problematic as it is highly mobile in the soil-water environment following application. Here, an agri-environmental scheme (AES) was introduced to a large-scale catchment (384 km2) to potentially reduce the burden of pesticides in the water treatment process. The main measure offered was contractor application of glyphosate by weed wiping as a substitute for boom spraying of MCPA, supported by educational and advisory activities. A combined innovation applied in the assessment was, i) a full before-after-control-impact (BACI) framework over four peak application seasons (April to October 2018 to 2021) where a neighbouring catchment (386 km2) did not have an AES and, ii) an enhanced monitoring approach where river discharge and MCPA concentrations were measured synchronously in each catchment. During peak application periods the sample resolution was every 7 h, and daily during quiescent winter periods. This sampling approach enabled flow- and time-weighted concentrations to be established, and a detailed record of export loads. These loads were up to 0.242 kg km−2 yr−1, and over an order of magnitude higher than previously reported in the literature. Despite this, and accounting for inter-annual and seasonal variations in river discharges, the AES catchment indicated a reduction in both flow- and time-weighted MCPA concentration of up to 21% and 24%, respectively, compared to the control catchment. No pollution swapping was detected. Nevertheless, the percentage of MCPA occurrences above a 0.1 μg L−1 threshold did not reduce and so the need for treatment was not fully resolved. Although the work highlights the advantages of catchment management approaches for pollution reduction in source water catchments, it also indicates that maximising participation will be essential for future AES.

Growth, development, and chlorophyll indexes of glyphosate and glufosinate-tolerant maize under herbicide application

Glyphosate, glufosinate, and atrazine do not affect the growth and development of glyphosate and glufosinate-tolerant (RR2/LL) maize; however, the results are less consolidated for these herbicides applied in mixtures. The aim of the present study was to evaluate the effects of post-emergent application of glyphosate, glufosinate, and atrazine, alone and in mixtures, on the growth and development of the RR2/LL maize. The treatments consisted of the application of glyphosate (1080 g of acid equivalent [ae] ha-1), glufosinate (500 g of active ingredient [ai] ha-1), atrazine (2000 g [ai] ha-1), glyphosate + glufosinate, glyphosate + atrazine, glufosinate + atrazine, glyphosate + glufosinate + atrazine, and the control (without application). The experiment was carried out in two locations under greenhouse conditions with different maize hybrids. Crop injury and variables of the agronomic performance (height, stem diameter, chlorophyll indexes, fresh and dry weight of shoot, root dry weight, and total dry weight) were evaluated. Herbicides applied alone or in binary mixtures did not cause major damage. However, the application of the three associated herbicides in some situations might result in detrimental effects on the development of the RR2/LL maize.