Rates Of Glyphosate Research Articles

Leaching of Glyphosate and AMPA from Field Lysimeters

Leaching of glyphosate and AMPA as affected by the time elapsed between the spraying and first leaching event was studied on large-scale lysimeters in a two-year study. The leaching events were induced by irrigation interventions able to deliver 336 L, equivalent to a rainfall of 40 mm. Four groups of three lysimeters were randomly selected between the 12 lysimeters available. They were irrigated on either one day after herbicide treatment (1 DAT), 7 DAT, 14 DAT or 28 DAT. The same group of lysimeters were irrigated a second time 14 days after the first irrigation, corresponding to a period of time of 15 DAT (1 + 14), 21 DAT (7 + 14), 28 DAT (14 + 14) and 42 DAT (28 + 14). In both years, lysimeters were sprayed with glyphosate (360 L ha−1) at a rate of 12 L ha−1, the maximum field rate allowed on the label. Our results pointed out that the leaching of glyphosate and AMPA is effectively event-driven and highlighted the importance of the first rainfall event in moving glyphosate through the soil, increasing the potential risk of water contamination. Overall, both chemicals showed a risk of water contamination. Glyphosate may persist more than usually considered, and its residues were found in leached waters from lysimeters treated 30 days before the leaching event. Other factors may affect the movement of these two compounds through the soil profile after spraying: temperature pattern and soil moisture. Finally, the results of this study refer to a very high application rate of glyphosate. Hence, at lower field rates, observed concentrations can likely be minor.

Sensitivity of rice to low rates of glyphosate and glyphosate plus dicamba at multiple growth stages

AbstractOff‐target movement of glyphosate can be severely injurious to rice (Oryza sativa L.). Glyphosate is routinely mixed with dicamba and applied to crops with resistance to both herbicides, such as glyphosate‐ and dicamba‐resistant corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] cultivars. This research was conducted to evaluate the effects of low rates of glyphosate and glyphosate plus dicamba on rice at multiple application timings. Separate field experiments were conducted and were repeated in 2018 and 2019 near Stuttgart, AR. The first experiment evaluated rice's response to glyphosate alone; a second experiment evaluated responses to glyphosate applied as a mixture with dicamba over several rice growth stages. The rates of glyphosate alone evaluated were 0.023, 0.047, 0.187, and 0.375 oz acid equivalent (ae) acre–1. Mixtures of glyphosate plus dicamba were evaluated at 0.050 plus 0.025, 0.2 plus 0.1, and 0.8 plus 0.4 oz ae acre–1, respectively. Visible injury to rice from glyphosate alone was never more than 3%, averaged over application timings. Unique symptomology and greater yield losses were observed for glyphosate mixed with dicamba. There was no reduction in rough rice grain yield after treatment with glyphosate alone. For the glyphosate plus dicamba experiment, no more than 13% injury occurred from any treatment. Rough rice grain yield was reduced by 21% relative to the nontreated control for the highest rate of glyphosate plus dicamba, averaged over application timings. Care should be taken to prevent off‐target movement of mixtures of glyphosate plus dicamba to neighboring rice.

Response of Imidazolinone-Resistant Sunflower to Various Drift Rates of Glyphosate, Glufosinate and Indaziflam

Imidazolinone (IMI) herbicides are used in sunflower due to the need for sunflower broomrape control, and IMI - resistant sunflower has become common in Turkey. Cereal fields and orchards are often in close vicinity to sunflower fields, and herbicide drift from these areas can adversely affect sunflower. Fields experiments were conducted at Edirne and Ankara, Turkey, in 2018 and 2019 to quantify the sunflower (IMI - resistant) response to various simulated drift rates of glyphosate, glufosinate, and indaziflam. Herbicides were applied to sunflower at 12.5, 6.25, 3.125, and 1% of recommended rates. Crop injury was visually evaluated at 7, 14, and 28 d after treatment (DAT), and plant responses to herbicides were assessed at harvest. Sunflower was injured by all rates of glyphosate applied, with 15 to 100% (in Edirne) and 9 to 84% (Ankara) injury at 28 DAT. Glufosinate - related injury was 5 to 58% in Edirne and 7 to 43% in Ankara at 7 DAT, and decreased with time. In contrast, indaziflam caused no significant crop injury or yield losses. The recommended rates of 6.25% and 12.5 of glyphosate killed all sunflower plants in 2019, while in 2018 the yield loss was 100% only at recommended rate of 12.5% glyphosate. Lower rates of glyphosate reduced yield by 2 to 87% in 2018 and 18 to 62% in 2019. On the other hand, the two highest rates of glufosinate resulted in a yield reduction of 9 and 6% in 2018, respectively, but not in 2019. Injury at early stages after exposure is a good indicator of the impact of glyphosate drift on sunflower yield.

Evaluation of newly established buffalograss for tolerance to glyphosate

AbstractBuffalograss [Buchloe dactlyoides (Nutt.) Engelm.] is gaining popularity as a turfgrass for low maintenance sites, where irrigation and regular mowing or fertility may not be available. Unfortunately, weed species also thrive in low maintenance sites. This field study was conducted to assess the utility of glyphosate as a selective herbicide in newly established buffalograss. Buffalograss (cultivar Cody) burs were sown into newly renovated sites in Fayetteville, AR, in the summer of 2017 and 2018. Glyphosate was applied at 1, 3, and 8 weeks after emergence (WAE) of buffalograss seedlings at rates of 0.15, 0.325, 0.75, 1.5, 3.0 lb a.e. acre–1 of glyphosate and one untreated control. These rates correspond to 0.1 time (×), 0.25×, 0.5×, 1.0×, and 2.0× of the highest labeled rate of 1.5 lb a.e. acre–1 of glyphosate (64 fl oz acre–1, RoundUp Pro, Bayer Cropscience). Following application, plots were assessed using visual ratings of turf quality on a 1–9 scale at weekly intervals for 10 weeks. One week after applications at 8 WAE, images were taken of each plot and analyzed for dark green color index (DGCI) as a quantified measure for the green value of living foliage in treated areas. In both years and all application timings, buffalograss turf quality was reduced to an unacceptable quality when treated with glyphosate at 0.25× of the maximum labeled rate and above. At the 0.1× rate of glyphosate, buffalograss turf quality was not significantly reduced in either year at any application timing.

Biochemical and genotoxic effects of some pesticides on the Egyptian Toads, Sclerophrys regularis (Reuss, 1833)

The effect of the 1/10 the application rates of either copper sulfate, temephos, glyphosate, or bifenthrin on some biochemical and genotoxic markers of the Egyptian toads, Sclerophrys regularis, exposed for 96 hours under conditions similar to the real situation was investigated. The results illustrated that , brain acetylcholinesterase (AChE) was significantly inhibited following temephos treatment, while the enzyme activities markedly increased following either glyphosate or bifenthrin exposure. Liver glutathione-S-transferase (GST) activity was inhibited following either copper sulfate or bifenthrin, while the activity increased following glyphosate treatment. Also, the data illustrated that, The level of glutathione reduced (GSH) in liver and the activities of lactic dehydrogenase (LDH), transaminasaes (AST and ALT), and phosphatases (ACP and ALP) in liver and serum showed significant increases following all the treatments and bifenthrin was the potent one. Regarding the genotoxicity of the tested pesticides, the number of structural aberrations induced by the different treatments was enumerated in the present study. It was found that all the tested pesticides significantly increased either the frequency of abnormalities or the number of polychromatic erythrocytes (PCE) per 1000 cells (the frequency of micronucleus, MN) compared to the negative control, where bifenthrin and temephos were found to be more potent than cyclophosphamide (positive control) to induce these structural aberrations. According to the present results, the tested concentrations of the tested pesticides could lead to a collapse of cellular homeostasis and changes in the biochemical and genetic parameters in the Egyptian toads which can be considered as indicators of environmental pollution by pesticides.

Safflower (Carthamus Tinctorius L.) Response to Drift Rates of Glyphosate

The paper presented the field studies carried out in Ankara during 2017- 2019 to established the safflower responses (Carthamus tinctorius L. var. Remzibey-05) to drift rates of glyphosate. The herbicide at the rate of 18, 9, 4.5 and 1.44 g active ingredient (a.i.) ha-1 was applied at a spray volume of 19.2 L ha-1 to safflower seedlings at 2-4 true leaf stage using a CO2 pressurized knapsack sprayer. Crop injury and yield reduction caused by the herbicide was determined at 28 days after treatment (DAT) and at harvest. As the drift dose of glyphosate increases, the phytotoxicity occurring in the safflower plant also increases and reached to 68.75-73.75% 28 DAT. Yield reduction caused by the lowest drift rate of glyphosate was limited, 13-25%, compared to the nontreated control. At the highest drift dose, the plants could not produce spike and seeds.

Managing bermudagrass competition to overseeded alfalfa

AbstractOverseeding alfalfa (Medicago sativa L.) into existing bermudagrass [Cynodon dactylon L. (Pers.)] swards may reduce N fertilizer inputs and improve seasonal distribution of forage. However, achieving successful alfalfa stands in mixture with bermudagrass is difficult because of competition from the grass. This experiment's objective was to assess strategies for managing bermudagrass competition to alfalfa during establishment and subsequent stand life. During 2020 and 2021, a 2 × 2 × 2 factorial was replicated five times in a randomized complete block design. The treatment factors included the glyphosate rate [N‐(phosphonomethyl) glycine], the initial bermudagrass stubble height (SH), and N fertilizer rates. Before planting alfalfa in November 2019, bermudagrass swards were treated with glyphosate at 0 or 890 ml ha–1 and clipped to a SH of 5 or 15 cm. During harvest seasons, N fertilizer was applied at 0 or 40 kg N ha–1 harvest–1. Glyphosate and SH had minimal effect on alfalfa establishment, forage accumulation (FA), and persistence. Application of N in 2020 increased mixture (34%) and bermudagrass (30%) FA over zero N, but alfalfa FA and proportion in mixture FA were not affected by N. In 2021, mixture FA was not affected by N, but alfalfa FA (5,030 vs. 2,380 kg ha–1) and proportion (63 vs. 25%) were greater for 0 than for the 40 kg N ha–1 rate. We conclude that N application increases first‐year alfalfa–bermudagrass mixture FA by increasing bermudagrass production, but it reduces second‐year alfalfa contribution, resulting in lesser alfalfa FA and mixture nutritive value and a shorter harvest season.

Effect of elevated temperature on growth and glyphosate susceptibility of Chloris truncata R.Br., Sonchus oleraceus L., and Conyza bonariensis (L.) Cronq.

ABSTRACT A temperature-controlled glasshouse study was conducted to evaluate the influence of elevated temperature (eT – 34/24 ± 2°C) on the growth and glyphosate susceptibility of windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronquist]; and to determine the morpho-physiological factors involved in differential glyphosate tolerance under eT. Results showed that elevation of temperature from ambient temperature (aT – 28/20 ± 2°C) to 34/24 ± 2°C increased growth and biomass production of C. truncata. In contrast, eT suppressed growth of S. oleraceus and C. bonariensis, resulting in fewer, thicker, and smaller leaves with reduced stomatal conductivity and less total plant biomass. In terms of herbicide susceptibility, the responses to glyphosate under different temperature regimes were species- and rate-specific. Slight variations in glyphosate susceptibility were observed when sprayed at sub-lethal rates at eT. Under eT, C. truncata, S. oleraceus, and C. bonariensis required 1.5, 2.0-, and 1.6-times higher glyphosate rates, respectively, to suppress biomass by 50% compared with plants grown at aT. Depending upon the species and glyphosate rate, differences in leaf characteristics (i.e. leaf chlorophyll content, leaf area/thickness, and stomatal conductance) could have promoted or delayed glyphosate activity under eT over the period, especially at sub-lethal rates. Overall, the glyphosate efficacy was unaffected since herbicide within the recommended rates completely controlled all tested weed species under both temperatures. Nomenclature: windmill grass, Chloris truncata R.Br., Common sowthistle, Sonchus oleraceus L., Flaxleaf fleabane, Conyza bonariensis (L.) Cronquist

Effect of Soil Moisture Regimes on the Glyphosate Sensitivity and Morpho-Physiological Traits of Windmill Grass (Chloris truncata R.Br.), Common Sowthistle (Sonchus oleraceus L.), and Flaxleaf Fleabane [Conyza bonariensis (L.) Cronq.

The glasshouse study was conducted with the objectives of (i) investigating the effect of soil moisture variations on the control efficiency of glyphosate on windmill grass (Chloris truncata R.Br.), common sowthistle (Sonchus oleraceus L.), and flaxleaf fleabane [Conyza bonariensis (L.) Cronq.], (ii) evaluating the tolerance of tested weed species under soil moisture variations, and (iii) determining the morphological and physiological characteristics of these species to partially explain herbicide tolerance under periods of reduced soil moisture availability (RSM). The species’ tolerance to glyphosate increased significantly under reduced soil moisture availability (p < 0.001). The lethal dose to cause herbicide injury or biomass reduction by 50% (LD50) and 80% (LD80) in relation to untreated control for water-stressed plants [i.e., moderate soil moisture availability (MSM) and RSM] was significantly higher than that of plants grown under high soil moisture availability (HSM). The tolerance factor (TF) for C. truncata, S. oleraceus, and C. bonariensis, in terms of biomass reduction under RSM, was 2.6, 2.4, and 2.6, respectively, as compared to HSM. The results showed that the glyphosate sensitivity, especially at the sub-lethal rates, of the three weed species under study decreased as soil moisture availability reduced (p < 0.01). Overall glyphosate efficacy, in relation to the recommended rate, was unaffected, except for C. truncata; the weed survived the highest tested glyphosate rate [750 g active ingredient (a.i.) ha−1] under RSM. There was significant interaction between weed species and soil moisture regimes for weed morpho-physiological traits (p < 0.001), with reduced soil moisture having a more influential impact on the growth of C. bonariensis and S. oleraceus compared to C. truncata. Changes in the leaf characteristics, such as increased leaf thickness, higher leaf chlorophyll content, reduced leaf area, and limited stomatal activity for all the tested weed species under MSM and RSM in relation to HSM, partially explain the tolerance of species to glyphosate at sublethal rates.

Effect of EPSPS gene copy number and glyphosate selection on fitness of glyphosate-resistant Bassia scoparia in the field

The widespread evolution of glyphosate-resistant (GR) Bassia scoparia in the U.S. Great Plains poses a serious threat to the long-term sustainability of GR sugar beet. Glyphosate resistance in B. scoparia is due to an increase in the EPSPS (5-enolpyruvyl-shikimate-3-phosphate) gene copy number. The variation in EPSPS gene copies among individuals from within a single GR B. scoparia population indicated a differential response to glyphosate selection. With the continued use of glyphosate in GR sugar beet, the effect of increasing glyphosate rates (applied as single or sequential applications) on the fitness of GR B. scoparia individuals with variable EPSPS gene copies was tested under field conditions. The variation in EPSPS gene copy number and total glyphosate rate (single or sequential applications) did not influence any of the reproductive traits of GR B. scoparia, except seed production. Sequential applications of glyphosate with a total rate of 2214 g ae ha−1 or higher prevented seed production in B. scoparia plants with 2–4 (low levels of resistance) and 5–6 (moderate levels of resistance) EPSPS gene copies. Timely sequential applications of glyphosate (full recommended rates) can potentially slow down the evolution of GR B. scoparia with low to moderate levels of resistance (2–6 EPSPS gene copies), but any survivors (highly-resistant individuals with ≥ 8 EPSPS gene copies) need to be mechanically removed before flowering from GR sugar beet fields. This research warrants the need to adopt ecologically based, multi-tactic strategies to reduce exposure of B. scoparia to glyphosate in GR sugar beet.

Evaluation of Chemical Control Methods of Fountain Grass

Fountain grass (Pennisetum alopecuroides) is a common ornamental grass because of its glossy foliage and showy inflorescence. However, there have been reports of populations growing outside of cultivation and demonstrating invasive tendencies. There is limited research of the chemical control of fountain grass in natural areas. The objective of this experiment was to evaluate the impact of glyphosate, sethoxydim, and fluazifop on fountain grass. Treatments consisted of 2250 and 4500 g⋅ha–1 glyphosate, 262.5 and 525 g⋅ha–1 sethoxydim, and 200 and 400 g⋅ha–1 fluazifop; a nontreated control group was also included. The percent herbicide injury was determined visually 1, 3, 4, 6, and 10 weeks after treatment (WAT). Both rates of glyphosate resulted in 100% of the foliage injured by 3 WAT. The application of flauzifop and sethoxydim led to intermediate results ranging from 15% to 23% injury by 6 WAT, with no significant difference between active ingredients or rates. Nontreated control plants exhibited little to no injury throughout the study. Flauzifop, sethoxydim, and glyphosate all caused visible injury to fountain grass. For complete, fast-acting control, glyphosate is recommended. Herbicide control coupled with restorative plantings of native plants can help reduce invasive plant pressure and improve biodiversity of natural areas.

Fate and adaptive plasticity of heterogeneous resistant population of Echinochloa colona in response to glyphosate

Understanding the fate of heterogenous herbicide resistant weed populations in response to management practices can help towards overcoming the resistance issues. We selected one pair of susceptible (S) and resistant (R) phenotypes (2B21-R vs 2B21-S and 2B37-R vs 2B37-S) separately from two glyphosate resistant heterogeneous populations (2B21 and 2B37) of Echinochloa colona and their fate and adaptive plasticity were evaluated after glyphosate application. Our study revealed the glyphosate concentration required to cause a 50% plant mortality (LD50) was 1187, 200, 3064, and 192 g a. e. ha−1 for the four phenotypes 2B21-R, 2B21-S, 2B37-R, and 2B37-S respectively. Both S phenotypes accumulated more biomass than the R phenotypes at the lower application rates (34 and 67.5 g a. e. ha−1) of glyphosate. However, the R phenotypes generally produced more biomass at rates of glyphosate higher than 100 g a. e. ha−1 throughout the growth period. Plants from the R phenotypes of 2B21 and 2B37 generated 32% and 38% fewer spikes plant−1 than their respective S counterparts in the absence of glyphosate respectively. The spike and seed numbers plant-1 significantly higher in R than S phenotypes at increased rates of glyphosate and these relationships were significant. Our research suggests that glyphosate-resistant E. colona plants will be less fit than susceptible plants (from the same population) in the absence of glyphosate. But in the presence of glyphosate, the R plants may eventually dominate in the field. The use of glyphosate is widespread in field, would favour the selection towards resistant individuals.

Effect of glyphosate and glufosinate on nutritional content and agronomic performance of maize possessing cp4epsps and pat transgenes

The aim of this study was to check the tolerance level of maize possessing the transgenes cp4epsps and pat, exposed to high rates of glyphosate or glufosinate. Field experiments were carried out in 2016/17 at the first growing season; and the other in the second growing season, in Palotina, state of Paraná (PR), Brazil. The design was completely randomized block with 4 replications, which were set up with variations of rates of herbicides: glyphosate (0; 2,160; 4,320; 6,480 and 8,640 g ae ha-1) (experiment 1) and glufosinate (0; 1,500; 3,000; 4,500 and 6,000 g ai ha-1) (experiment 2). The application was performed at the V4 stage. Plants were evaluated for injuries, final plant height, stem diameter, 100-grain mass, yield and content of P, K, S, Fe, Cu and Zn. The results show that there was no reduction in yield and 100-grain mass, as well as changes in nutrient contents, even with the use of high rates of glyphosate and glufosinate. This is explained by the rapid recovery of maize hybrids under favorable developmental conditions. Despite causing injuries and decreased height, application of glyphosate (up to 8,640 g ae ha-1) or glufosinate (up to 6,000 ai ha-1) did neither reduce yield and 100-grain mass nor the nutrient contents of grains. This shows the high selectivity of these herbicides. Nonetheless, crop injury and reduction in height were observed in maize plants for herbicide application. This indicates the risks of using herbicides above the rates recommended in the package insert, despite the absence of deleterious effects on yield

Effect of Different Climate Change Variables on the Ecology and Management of Sesbania cannabina through Glyphosate.

An elevated atmospheric carbon dioxide (CO2) concentration and frequent droughts are two anticipated climate change scenarios in which certain invasive weeds may develop competitive advantages over crops and adversely impact productivity and herbicide efficacy. Hence, a study was conducted to explore the effect of different climatic scenarios on the growth and management of Sesbania cannabina (Retz.) Pers with glyphosate. The variables investigated were two CO2 concentrations (400 and 700 ppm), two soil moisture levels (100% and 50% of field capacity (FC)), and three glyphosate rates (0 (control), 517 (50% of recommended rate), and 1034 g ae ha−1 (recommended rate)). CO2 concentrations and soil moisture levels had different effects on the growth and management of S. cannabina. Overall, 100% FC and elevated [CO2] of 700 ppm recorded the maximum plant height (38 cm), leaves per plant (20), growth index (60), chlorophyll content (SPAD value 37), and dry biomass (3 g) in comparison with ambient [CO2] of 400 ppm and 50% FC treatment. The recommended glyphosate application gave 100% weed biomass reduction; however, efficacy was reduced (63%) when applied at 50% of the recommended rate under elevated [CO2] of 700 ppm and 50% FC conditions.

Modified zeolite-supported biofilm in service of pesticide biodegradation.

The development of biofilms on modified natural zeolites was investigated with purpose to obtain biocomposites with biodegradation activity towards pesticides MCPA (2-methyl-4-chlorophenoxyacetic acid) and glyphosate (N-(phosphonomethyl)glycine) for potential application in bioaugmentation of polluted agricultural soils. Microbial communities were selected from agricultural pesticide-contaminated soil/water samples and enriched on the basis of their ability to biodegrade the pesticides. In order to enhance affinity of microbial communities to the support material, the natural mineral zeolite was modified by nontoxic environmentally friendly cations (Li+, Na+, K+, NH4+, H+, Mg2+, Ca2+, Fe3+) by methods preserving its structure and characterised using powder XRD, surface area measurement and chemical composition analysis. Kinetics of pesticide degradation by the biocomposites was studied in liquid media. Results showed that according to zeolite modifications, the microbial activity and biodiversity changed. The best biodegradation rate of MCPA and glyphosate reached 0.12-0.13 mg/h with half-life of 16-18 h, which is considerably quicker than observed in natural environment. However, in some cases, biodegradation activity towards pesticides was lost which was connected to unfavourable zeolite modification and accumulation of toxic metabolites. High-throughput sequencing on the 16S rRNA genes of the biofilm communities highlighted the selection of bacteria genera known to metabolise MCPA (Aminobacter, Cupriavidus, Novosphingobium, Pseudomonas, Rhodococcus, Sphingobium and Sphingopyxis) and glyphosate (Pseudomonas). Altogether, results suggested that zeolites do not only have a passive role of biofilm support but also have protective and nutrient-supportive functions that consequently increase biodiversity of the pesticide degraders growing in the biofilm and influence the pesticide biodegradation rate.

Using Machine Learning and Hyperspectral Images to Assess Damages to Corn Plant Caused by Glyphosate and to Evaluate Recoverability

Glyphosate is the most widely used herbicide in crop production due to the widespread adoption of glyphosate-resistant (GR) crops. However, the spray of glyphosate onto non-target crops from ground or aerial applications can cause severe injury to non-GR corn plants. To evaluate the crop damage of the non-GR corn plants from glyphosate and the recoverability of the damaged plants, we used the hyperspectral imaging (HSI) technique in field experiments with different glyphosate application rates. This study investigated the spectral characteristic of corn plants and assessed the corn plant damage from glyphosate. Based on HSI image analysis, a spectral variation pattern was observed at 1 week after treatment (WAT), 2 WAT, and 3 WAT from the glyphosate-treated non-GR corn plants. It was further found that the corn plants treated with glyphosate rates equal to or higher than 0.5X (X = 0.866 kilograms acid equivalents/hectare (kg ae/ha) represents the recommended spray rate for GR corn) would suffer unrecoverable damage. Using the Jeffries–Matusita distance as the spectral sensitivity criterion, three sensitive bands from the measured spectra were selected to create two spectral indices for crop recoverability differentiation in band ratio and normalization forms, respectively. With the two spectral indices, the corn plants recoverable and unrecoverable from damage were classified with an overall accuracy greater than 95%. Then, three machine learning algorithms (k-nearest neighbors, random forest, and support vector machine) were respectively combined with the successive projections algorithm to create models to relate selected feature spectral bands to glyphosate spray rates. The results indicated that the models achieved reasonable accuracy, especially in the group of recoverable plants. This study illustrated the potential of the hyperspectral imaging technique for evaluating crop damage from herbicides and recoverability of the injured plants using different data analysis and machine learning modeling approaches for practical weed management in crop fields.

Growth regulation of bermudagrass (Cynodon dactylon) and zoysiagrass (Zoysia japonica) with glyphosate

Glyphosate can generate positive effects on turfgrass maintenance as a form of growth control by decreasing the expenses associated with mowing. However, there is little information about the effects of this herbicide on turfgrasses. This study aimed to evaluate the response of bermudagrass and zoysiagrass to the herbicide glyphosate as a growth regulator. Two studies were performed in a greenhouse and repeated at different times. The treatments involved application of glyphosate at 10 different rates (0, 5.625, 11.25, 22.5, 45, 90, 180, 360, 720, and 1.440 g ae ha−1) with four replicates. Evaluations of green cover by digital analysis, injury, and plant height were performed at 7, 14, 21, and 28 days after application, and shoot dry matter of clippings was determined for the last evaluation period. Bermudagrass and zoysiagrass presented variedtolerance to glyphosate toxicity. Overall, the digital analysis showed that green content was negatively influenced by the increase in visual injury caused by glyphosate application. Moreover, increasing the glyphosate rate decreased plant height and shoot dry matter in both turfgrasses. Glyphosate application rates up to 45 g ae ha−1 for bermudagrass and 90 g ae ha−1 for zoysiagrass decreased plant growth without affecting the factors analyzed in this study.

Multiple herbicide-resistant Palmer amaranth (Amaranthus palmeri) in Connecticut: confirmation and response to POST herbicides

AbstractPalmer amaranth is the latest pigweed species documented in Connecticut; it was identified there in 2019. In a single-dose experiment, the Connecticut Palmer amaranth biotype survived the field-use rates of glyphosate (840 g ae ha−1) and imazaquin (137 g ai ha−1) herbicides applied separately. Additional experiments were conducted to (1) determine the level of resistance to glyphosate and acetolactate synthase (ALS) inhibitors in the Connecticut-resistant (CT-Res) biotype using whole-plant dose-response bioassays, and (2) evaluate the response of the CT-Res biotype to POST herbicides commonly used in Connecticut cropping systems. Based on the effective dose required for 90% control (ED90), the CT-Res biotype was 10-fold resistant to glyphosate when compared with the Kansas-susceptible (KS-Sus) biotype. Furthermore, the CT-Res biotype was highly resistant to ALS-inhibitor herbicides; only 18% control was achieved with 2,196 g ai ha−1 imazaquin. The CT-Res biotype was also cross-resistant to other ALS-inhibitor herbicides, including chlorimuron-ethyl (13.1 g ai ha−1), halosulfuron-methyl (70 g ai ha−1), and sulfometuron-methyl (392 g ai ha−1). The CT-Res Palmer amaranth was controlled 75% to 100% at 21 d after treatment (DAT) with POST applications of 2,4-D (386 g ae ha−1), carfentrazone-ethyl (34 g ai ha−1), clopyralid (280 g ae ha−1), dicamba (280 g ae ha−1), glufosinate (595 g ai ha−1), lactofen (220 g ai ha−1), oxyfluorfen (1,121g ai ha−1), and mesotrione (105 g ai ha−1) herbicides. Atrazine (2,240 g ai ha−1) controlled the CT-Res biotype only 52%, suggesting the biotype is resistant to this herbicide as well. Here we report the first case of Palmer amaranth from Connecticut with multiple resistance to glyphosate and ALS inhibitors. Growers should proactively use all available weed control tactics, including the use of effective PRE and alternative POST herbicides (tested in this study), for effective control of the CT-Res biotype.

Replace of the EPOST glyphosate with pre herbicides and application of different LPOST glyphosate rates for weed control in established vineyard

Two-year field trials were conducted at two winegrowing districts (Kavadarci and Skopje in 2016 and 2017) to evaluate wheather oxyfluorfen, pendimethalin and flazasulfuron can replace early post-emergence (EPOST) application of glyphosate in established vineyard until its application in early summer period. The weed vegetation in vineyards in both years was consisted mainly of Chenopodium album L., Setaria viridis (L). Beauv., Papaver rhoeas L., Xanthium strumarium L., Lolium multiflorum Lam., Sorghum halepense (L.) Pers. and Cynodon dactylon (L.) Pers. Pendimethalin, oxyfluorfen and flazasulfuron efficiently reduced predominant annual weeds and S. halepense seedlings in 2017, but not in 2016. PRE herbicides, regardless year, had no significant effect on C. dactylon. Opposite, the efficacy of EPOST applied glyphosate was significantly lower in 2017 compared to 2016. LPOST glyphosate applied at 2.0 l ha-1 provided at least 94 % control of dominant annual broadleaf and grass weeds. LPOST application of glyphosate at 2.0 l ha-1 and glyphosate at 2.0 and 4.0 l ha-1 resulted in unsatisfactory weed control of predominant perennial S. halepense, and C. dactylon, respectively. LPOST glyphosate applied at 4.0 l ha-1 provided control of S. halepense by 84 % or more. LPOST glyphosate applied at 8.0 l ha-1 reduced the amount of S. halepense and C. dactylon at least 97 %. Grapevine yield of both varieties was not lower in all herbicide treatments in 2016 compared with 2017. However, yield in the PRE herbicide treatments fb 2.0 and 4.0 l ha-1 glyphosate was collectively 15-19 % and 17-19 % lower compare to PRE herbicide treatments fb 8.0 l ha-1 glyphosate and standard two applications of glyphosate, respectively for both years and districts. No impacts to grapevine growth were observed from PRE herbicide treatments at either district

INTERAÇÃO E EFICÁCIA DE MISTURAS EM TANQUE DOS HERBICIDAS SAFLUFENACIL E GLYPHOSATE

O uso repetitivo do herbicida glyphosate e em elevadas doses tem selecionado biótipos de plantas daninhas resistentes, além de favorecer à seleção de plantas tolerantes ao mesmo. A solução mais comum nestes casos é a inclusão de herbicidas alternativos no sistema de produção, aplicados de forma isolada ou misturados em tanque. Desta forma, este trabalho foi desenvolvido com o objetivo de avaliar a eficácia e a interação de misturas de saflufenacil com o herbicida glyphosate para controle de plantas daninhas. Foram desenvolvidos dois experimentos independentes, avaliando-se duas espécies de plantas daninhas, uma monocotiledônea (capim-amargoso - Digitaria insularis) e uma dicotiledônea (corda-de-viola - Ipomoea triloba). Os tratamentos constaram de esquema fatorial 4x4, com quatro doses do herbicida glyphosate (0, 360, 720 e 1.080 g e.a. ha-1) e quatro doses do herbicida saflufenacil (0, 21, 42 e 63 g ha-1). Em ambos os trabalhos se adotou delineamento experimental de blocos ao acaso e cinco repetições. Dentre as combinações testadas, a mistura foi considerada aditiva para o capim-amargoso e para a corda-de-viola. Estas misturas foram consideradas importantes ferramentas para controle de plantas daninhas resistentes e tolerantes nos sistemas de produção, sendo o saflufenacil uma excelente molécula a ser utilizada em acompanhamento ao herbicida glyphosate.