Glyphosate Drift Research Articles

Effects of simulated glyphosate drift to native prairie plants and canola-compatible Brassicaceae species of North Dakota, United States

This study evaluated effects to native plant and weedy Brassicaceae species growing in areas potentially affected by drift of glyphosate used with glyphosate-resistant canola (Brassica napus). Ten native grass and forb species were selected based on importance in prairie areas of North Dakota, US; and four introduced Brassicaceae species (Brassica juncea, Brassica nigra, Brassica rapa, and Sinapis arvensis ssp. arvensis) were selected based on their ability to cross with B. napus. Greenhouse-grown seedlings were treated with 0 (carrier control), 0.00056, 0.0032, 0.018 and 0.1 × a field application rate (FAR) of 829 g ha−1 acid glyphosate (g acid equivalent or a.e. ha−1), along with no spray plants; with each treatment repeated in two experiments. Shoot dry weight and height were measured 14 days after treatment, and data were subjected to analysis of variance or covariance followed by a Dunnett's multiple comparison test to obtain No-Observed-Adverse-Effect-Rates (NOAERs) for both parameters. A Weibull regression was used to obtain the rate producing a 25% reduction (ER25) for shoot dry weight or height for a limited number of species and experiment combinations. Based on NOAER values for both shoot dry weight and height, most native species had reductions in growth with 0.1 × FAR resulting in NOAERs of 0.018 × FAR for at least one experiment. Nassella viridula was the most sensitive native species, with a NOAER of 0.0032 × FAR for shoot dry weight and one experiment for height. The Brassicaceae species responded similarly to glyphosate as the native species, with NOAER values ranging from 0.0032 to 0.018 × FAR. Only four species had valid regression analyses for shoot dry weight or height resulting in ER25 values between 0.007 and 0.054 × FAR. Pascopyrum smithii and Schizachyrium scoparium were not affected by glyphosate as indicated by NOAER values. This study indicated that drift concentrations between approximately 0.003, but more commonly ≥0.1 × FAR (2.49 and 82.9 g ha−1 acid glyphosate, respectively) may affect the growth and potential competitiveness of selected native plant species, and Brassicaceae species sexually compatible with glyphosate-resistant B. napus in North Dakota.

Simulated Drift of Dicamba and Glyphosate on Coffee Crop.

Weed management in areas adjacent to coffee plantations makes herbicide drift a constant concern, especially with the use of nonselective products such as dicamba. The objective of this study was to evaluate the phytotoxic effects of the herbicide dicamba alone and mixed with glyphosate as a result of simulated drift in a coffee-producing area. The study was conducted in duplicate at two different coffee cherry development stages. The study was performed with a randomized block design and a 2 × 5 + 1 factorial scheme with four replications using two herbicide spray solutions (dicamba and dicamba + glyphosate) and five low doses (0.25; 1; 5; 10; and 20%). Additionally, a control treatment without herbicide application was also employed. In this study, we evaluated the phytotoxic damage and biometric and productive parameters. Visual damages were observed with the use of dicamba and dicamba + glyphosate doses reduced by 0.25% to 5% in the first days after application. The main symptoms were new leaf epinasty, changes in the internodal distance, and plagiotropic branch curvature. Low doses led to reduced plant height and branch length. The treatments did not reduce productivity and performance but altered the physical classifications of grains.

Conventional corn tolerance to drift‐simulating rates of glyphosate at two growth stages

Core Ideas Conventional corn can tolerate low rates of glyphosate drift. Corn usually recovers from very low drift rates of glyphosate within three to five weeks after exposure. Generally, corn plants become less sensitive to glyphosate drift at later vegetative growth. Corn response to glyphosate drift may vary depending on the weather conditions following the exposure.

Peanut response to 2,4-D plus glyphosate

AbstractThe commercialization of crops that are resistant to 2,4-D plus glyphosate provided an opportunity to growers to apply the herbicide postemergence. However, the potential drift injury of these herbicides to peanuts grown near crops that are resistant to 2,4-D plus glyphosate is concerning. Field experiments were conducted in 2019 and 2020 to evaluate peanut response when exposed at 25, 50, and 75 d after planting (DAP) corresponding to vegetative, flowering, and pod development stages, respectively, to reduced rates of 1/512×, 1/128×, 1/32×, and 1/8× of the labeled rate of 2,4-D plus glyphosate (i.e., 1,077 + 1,132 g ae ha−1, respectively). 2,4-D plus glyphosate was more injurious to peanuts when exposed at 25 DAP compared with 50 and 75 DAP. Similarly, greater canopy height (12%) and canopy width (16%) reductions were observed at 25 DAP compared with 50 and 75 DAP exposure timings (3% to 9%). This result indicates that peanut is more sensitive to 2,4-D plus glyphosate exposure at the vegetative growth stage than at the flowering and pod development stages. However, yield reductions (13% to 16%) were not different between 25, 50, or 75 DAT exposure timings. Regression analysis indicated a linear response for peanut injury, canopy height, width, and yield reduction with an increasing rate of 2,4-D plus glyphosate. The highest rate of 2,4-D plus glyphosate (1/8× of the label rate) resulted in 38%, 22%, and 23% peanut injury, canopy height, and width reduction at 4 wk after treatment, and 33% yield reduction. There was a correlation between peanut injury and yield reduction, with Pearson’s rho values ranging from 0.70 to 0.73. The findings suggest that peanut injury rating data after 2,4-D plus glyphosate drift can be useful for estimating potential yield losses.

Hormese induzida por glifosato em cultivares de Urochloa com aplicação sequencial

Abstract Glyphosate is the most widely used herbicide and is responsible for a significant technical/productive advance in world agriculture. Glyphosate drift after its application to control weeds in agricultural fields can stimulate growth and/or productive performance in non-target plants, located adjacent to the treatment, characterizing the hormesis effect. However, the hormesis effect of glyphosate may be different depending on the plant species, its stage of development, and the applied dose. Considering the stimulus of forage biomass production for animal feed, this study aimed to assess the hormesis effect by successive applications of low glyphosate doses to cultivars of the genus Urochloa. The shoot and root productive responses of three grass cultivars (Urochloa brizantha cv. Marandu, U. brizantha cv. Piatã, and U. ruziziensis cv. Ruziziensis) were assessed in pots through leaf applications of subdoses of the acid equivalent (ae) of glyphosate (5.40, 10.80, 21.60, 43.20, and 86.40 g ae ha-1) and a control (no glyphosate application). Four sequential harvests, conducted with a frequency of 21 days in a completely randomized design and a 6 x 3 x 4 factorial arrangement, with three replications, were assessed. Doses equal to or higher than 43.20 g ae ha-1 of glyphosate, applied in two sequential applications impaired the biomass production of the assessed forages. Ruziziensis was the most susceptible cultivar to the phytotoxic effect. Sequential applications of the subdoses 5.40 and 10.80 g ae ha-1 of glyphosate characterized the hormesis effect, promoting the shoot and root biomass production of the forage plants U. brizantha cv. Marandu, U. brizantha cv. Piatã, and U. ruziziensis cv. Ruziziensis.

Biomarkers of pollution by glyphosate in the lichens, Parmotrema tinctorium and Usnea barbata.

Glyphosate is a herbicide commonly used in agriculture for weed control. Current agricultural production demands vast amounts of this product, which are applied by ground or aerial spraying. The concomitant aerial currents promote glyphosate drift to vegetated or urban areas. In this context, we hypothesized that the lichens, Parmotrema tinctorum and Usnea barbata, could be sensitive to the action of glyphosate and therefore be used to bio-indicate the presence of this herbicide in areas affected by drift. Since living organisms respond in different ways to the action of herbicides, our interest was also to indicate biological markers responsive to the action of glyphosate, through concentrations and exposure times of the thallus, besides identifying the most sensitive species. We evaluated the effect of different concentrations (0.0, 4.8, 9.6, and 19.2 mg L-1) and exposure times (24, 48, and 72 hours) to glyphosate on the morphoanatomy, photobiont vitality, photosynthetic efficiency, and oxidative metabolism of the thalli. We found that the lichens, P. tinctorum and U. barbata, respond to glyphosate stress, with prospects for use in the biomonitoring of pollutant dispersal from plantation areas. When using P. tinctorum as a bioindicator, lichen morphoanatomy, photobiont vitality, and photosynthetic pigment concentration were efficient biomarkers for the effect of concentration and exposure time. For U. barbata, the lichenic morphoanatomy and the activity of SOD and APX enzymes were essential tools to indicate the herbicide action. Parmotrema tinctotum, however, was characterized as more sensitive in bio-indicating the presence of this herbicide to diagnose the air quality in urban areas or vegetation sectors adjacent to agricultural environments.

The Climbing Swamp Fern, Stenochlaena palustris (Burm. F.) Bedd. (Blechnaceae) - A Noxious Weed in Oil Palm Estates and Its Management

The climbing swamp fern or Stenochlaena palustris, is a fern that has a creeping stem/rhizome which often grows into a vigorous sheet colony over large areas and climbs robustly on palm trunks as an epiphyte. The young shoots or new fronds of this fern are consumed as vegetables by humans. The fern has other usages in local medicine, basket making and a beneficial role in pest management. In a field with thick tall sheet growth of S. palustris, the harvesting, evacuation of fresh fruit bunch (FFB), loose fruit collection and many field operations will be difficult to be carried out efficiently. The luxurious epiphytic growth on palm trunk up into the canopy prevents the sighting and cutting of FFB during harvesting and thus many ripe FFB are left unharvested, which subsequently become over-ripe/ rotten. In both situations, oil palm yield in severely infested fields is badly impacted. In line with the integrated weed management approach, prevention of the establishment of S. palustris is important by early control of isolated colonies or small patches of this noxious weed in the replanting fields, drain sides and on trunk chips. In the control of this serious noxious weed, various measures applied singly or in combination are necessary in line with integrated weed management approach. Over the years, chemical control has been widely practiced in rubber and oil palm plantations. The herbicides including 2,4,5-T, paraquat, DSMA (disodium methyl arsonate), MSMA (monosodium methanearsonate), diuron, sodium chlorate, 2,4-D sodium, 2,4-D amine, imazapyr, glyphosate, glufosinate-ammonium, metsulfuron-methyl, saflufenacil and sulfentrazone (and mixtures) are briefly discussed and reviewed. To mitigate the removal of paraquat, several alternatives have been identified and reported by several researchers. The writer’s recommendations to control S. palustris for mature plantings are: i) sodium chlorate + metsulfuron-methyl at 5.5 kg + 75 g per hectare (or 220 g + 3 g per 18 L water), ii) glyphosate + metsulfuron-methyl at 1.5 L + 75 g per hectare (or 60 ml + 3 g per 18 L water), iii) glufosinate-ammonium at 3.3 L per hectare (or 132 ml per 18 L water). For control of S. palustris in inter-row areas of immature plantings, treatments i) and iii) are recommended. This is to avoid unacceptable phytotoxicity to spear and new fronds of immature palms due to spray drift of glyphosate. For long-term control of S. palustris in pure stand and in inter-row areas, spraying of metsulfuron-methyl at 150 g product per hectare (or 20% product in 6 g per 18 L water) is recommended. For spraying of epiphytic S. palustris and other mixed species of epiphytes, glyphosate + metsulfuron-methyl at 1.5 L + 75 g per hectare (or 60 ml + 3 g per 18 L water) is recommended and the optimum spraying time is after frond pruning operation. Keywords: Stenochlaena palustris, noxious weed, climbing epiphytic weed, oil palm plantations, management, herbicides.

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.

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.

Glyphosate in the production and forage quality of marandu grass

The drift of the herbicide glyphosate, used for desiccating crops or controlling weeds, can result in growth-promoting or non-target plant development effects. Thus, it is possible to use the compound to increase the biomass of forage through the hormone effect. The objective of this study was to evaluate the effects of sublethal doses of glyphosate on the production of Urochloa brizantha cv. Marandu (Marandu grass) and its nutritional quality in ruminants. The design used was completely randomized, with five replications in a factorial scheme. The treatments used were as follows: control (without glyphosate application) and four sublethal doses of glyphosate (4, 10, 14, and 20 g ha-1 of the acid equivalent). The monthly collections consisted of collecting the plant material (0.20 m) from the surface, comprising of leaves and pseudocolmos (stem and leaf sheath) to determine the dry matter production and forage chemical-bromatological parameters. The results showed that leaf/stem ratio, neutral detergent fiber, and acid detergent fiber were affected exclusively by the harvest factor. The hormone effect of the herbicide occurs in the production of dry matter and lignin in the evaluated subdoses. For crude protein, there was an interaction between the factor doses and harvest, due to the effect of glyphosate and the management applied to the harvests, showing that the sublethal doses of glyphosate promoted the production of dry matter and the food quality of Marandu grass.

Hydrogen peroxide, superoxide, lipid peroxidation and membrane damage in leaves of the tree Prosopis nigra (Fabaceae) under simulated glyphosate drift

Introduction: The tree Prosopis nigra is native to the Western Chaco phytogeographic region, affected by the application of glyphosate in the surrounding crops. Objective: To determine the impact of simulated glyphosate drift on growth, photosynthesis and oxidative stress in P. nigra seedlings. Methods: We simulated drift in seedlings at doses of 0, 200, 400 and 800 g a.e. ha-1 of glyphosate. We also measured gas exchange and modulated fluorescence emission of chlorophyll a. Results: Glyphosate reduced biomass, photosynthetic rate, and stomatal conductance. Doses of 400 and 800 g a.e. ha-1 glyphosate produced photoinhibition. The electron transport rate was sensitive to glyphosate, and it decreased at all doses of the herbicide. Glyphosate generated oxidative stress, and produced damage to membranes, because of the accumulation of H2O2 and O2.. Conclusions: Glyphosate reduces growth and photosynthesis in these seedlings. The inhibition of photosynthesis is due to stomatal closure, and alterations in the photochemical stage, associated with oxidative stress.

Effect of glyphosate drift on marandu grass

Glyphosate drift in plants that are not resistant to the herbicide molecule can result in stimulation to certain biological features, characterizing the phenomenon of hormesis. On this basis, productive and chemical traits were evaluated in marandu grass, in a simulation of the drift effect, using sublethal doses of the herbicide glyphosate. The experiment was in laid out in a randomized-block design with split plots in time, in four replicates. The effect of sublethal doses of glyphosate acid equivalent (a.e.) (21.60, 43.20, 64.80, 86.40 and 108.00 g ha-1) and control was evaluated in the plots; and the effect of harvesting at 92, 113, 134 and 155 days after sowing (DAS) the grass was evaluated in the subplots. The Urochloa brizantha cv. Marandu was collected at a height of 0.20 m, at a defoliation interval of 21 days, to estimate production and chemical traits, in experimental plots with a usable area of 7.5 m2. Leaf: stem ratio was influenced by the interaction between the evaluated factors (dose and harvest). Dose fitted a second-order polynomial model, with a hormesis effect of 21.60 to 76.50 g ha-1 of glyphosate a.e. Harvesting at 134 DAS differed significantly from 92 DAS. The forage yield showed a linear response inversely proportional to the increasing glyphosate doses. There was a polynomial increase in leaf phosphorus content, characterizing hormesis up to the sublethal dose of 72.50 g a.e. ha-1. Harvest influenced the neutral detergent fiber, acid detergent fiber, lignin and leaf phosphorus contents.

Effect of Fertiactyl® on the absorption and translocation of 14C-glyphosate in young eucalyptus plants

Fertiactyl® is a foliar fertilizer with the potential to minimize the phytotoxicity effects caused by glyphosate drift in eucalyptus plants. As the interactions of the glyphosate and Fertiactyl® in tank mix on the plant behavior are not yet known, the objective was to evaluate the absorption and translocation of 14C-glyphosate, applied isolated and mixed in tank with Fertiactyl®, in young eucalyptus plants (clone I-144, Eucalyptus urophylla x E. grandis). The addition of Fertiactyl® to the mixture of 14C-glyphosate reduced the absorption by 94.3% in relation to the total absorbed at the end of the evaluation compared to plants treated only with 14C-glyphosate, i.e., Fertiactyl® protected the eucalyptus plants of the glyphosate intoxication by drift. The translocation rates from the treated leaves to the rest of the shoots and roots were low (<2% of the total recovered) in both treatments, suggest that restricted translocation is a mechanism of natural tolerance to glyphosate in plants of clone I-144. It is concluded that Fertiactyl®, mixed in the solution with glyphosate, protects young eucalyptus plants against glyphosate drift by reducing the amount of herbicide absorbed.

Glyphosate effects on tree species natives from Cerrado and Caatinga Brazilian biome: Assessing sensitivity to two ways of contamination

Glyphosate is applied for dissection in no-till and post-emergence management in transgenic crops in agricultural fields near the Cerrado and Caatinga biomes. These biomes together represent 33.8% of the Brazilian territory, contributing to the maintenance of great world diversity in flora and fauna. Despite actions to protect them, the proximity with agricultural areas and intense use of glyphosate puts at risk the preservation of native vegetation due to the contamination via herbicide transport processes. Our objectives were: i) to determine the sensitivity of native species from the Cerrado and Caatinga to glyphosate contamination via drift and groundwater; ii) evaluate the level of sensitivity to glyphosate among the different organs of plants. The highest intoxications (upper 80%) were observed for Bauhinia cheilantha, Mimosa caesalpiniaefolia, Mimosa tenuiflora and Amburana cearensis due to drift simullation. The species with 90% of total dry matter reduction were Bauhinia cheilantha, Enterolobium contortisiliquum, Mimosa caesalpiniaefolia, Mimosa tenuiflora, Tabebuia aurea. B. cheilantha and M. tenuiflora are most affected by exposure to glyphosate drift, with 50% of total dry matter reduction when exposed to doses below 444,0 g ha−1. Leaf growth is more sensitive to glyphosate for drift exposure for most species. Hymenaea courbaril is an exception, with greater sensitivity to root growth (50% dry matter reduction at doses below 666,0 g ha−1). B. cheilantha is the species most sensitive to drift exposure; however, it showed complete tolerance to contamination in subsurface waters. Other species such as Anadenanthera macrocarpa and M. caesalpiniifolia are also sensitive to drift, but without reach 90% of total dry matter reduction. A. macrocarpa, M. caesalpiniifolia and T. aurea were tolerant to contamination by subsurface water. The differential tolerance of trees confirms glyphosate's potential as a species selection agent in the Cerrado and Caatinga biomes.

PHYSIOLOGICAL RESPONSES OF Eucalyptus camaldulensis (Dehnh.) TO SIMULATED GLYPHOSATE DRIFT

Weed control with glyphosate produces damages in plantations of Eucalyptus camaldulensis, although the involved physiological mechanisms have not been completely elucidated. This work aimed at assessing the physiological responses of E. camaldulensis to simulated glyphosate drift. Greenhouse trials were performed with four-month-old E. camaldulensis clone117 seedlings. The herbicide drift was simulated applying doses of 0; 43,2; 86,4; 172,8 and 345,6 g a.e. ha−1 glyphosate. Twenty-three days after the application, we measured gas exchange and chlorophyll a fluorescence. We also quantified Rubisco activity and indicator variables of oxidative stress. Glyphosate decreased carbon photosynthetic assimilation, increased non-photochemical quenching, induced stomatal closure, and increased photoinhibition. It also decreased Rubisco activity and increased photorespiration. The herbicide produced oxidative stress, and increased the activities in the enzymes catalase, ascorbate peroxidase, and superoxide dismutase, involved in the detoxification of reactive oxygen species. We concluded that glyphosate´s deleterious effects on the assimilation of CO2 in E. camaldulensis are due to stomatal and non-stomatal effects. The decrease in Rubisco activity, the increase in photorespiration, and photoinhibition stand out among non-stomatal effects. The increase in the activity of the antioxidant system is insufficient to compensate for the production of H2O2 in photorespiration, which damages the photosynthetic apparatus.

Damage to lemon tree caused by simulated drift of herbicides

The use of herbicides, in particular clomazone and glyphosate, applied in isolation or in a tank mix, is very common in rice, soybeans, corn and sugarcane fields and the drift of these herbicides can cause damage in sensitive species grown nearby. The purpose of this work was to evaluate the effects of the simulated drift of clomazone and glyphosate applied in an isolated way or mixed in a spray on lemon tree plants. The experiment was installed in a greenhouse in pots with a capacity of 15 L containing sieved soil and an experimental design of randomized blocks was adopted, arranged in a 3 x 5 factorial scheme, with four replications. Plants with two years of development were used. The treatments tested were, clomazone, glyphosate and both mixed, and the decreasing doses of the recommended commercial product: 100, 75, 50, 25 and 0% to simulate herbicide drift. Was evaluated variables, phytotoxicity at 14, 28, 46 and 100 days after application of treatments; plant height, crown volume, the trunk diameter of the rootstock, trunk diameter of the graft and trunk diameter at the grafting point at 0 and 100 days after application of treatments; and liquid assimilation of CO2 at 10 and 60 days after application of treatments. Among the tested herbicides, the one that presented the highest phytotoxicity and the lowest liquid assimilation of CO2 in lemon tree plants was the glyphosate + clomazone mixture. Increases in trunk diameter of the rootstock, grafting point, graft and crown volume did not show significant effects with simulated drift. The plant height presented a greater reduction with the increase of the herbicide doses, mainly glyphosate. That there are considerable losses in lemon tree plants when herbicide drift occurs, mainly by glyphosate and its mixture with clomazone.

Simulated derive of glyphosate in green onion plants (Allium fistulosum L.)

The effect of simulated glyphosate drift on common chives (Allium fistulosum L.) was evaluated. The work was developed in a private garden, in Confresa-MT, from January to February 2016. The experiment consists of 6 treatments with 4 repetitions, arranged in a completely randomized design (DIC). The treatments were formed b 6 sub doses of glyphosate: 0,54,108,162,216 and 270 g.i.a ha-1 . At 7 and 14 days after application of the sub doses of the herbicide glyphosate, the plants were subjected to visual analysis of phytointoxication, using notes, on a scale ranging from 0 to 10. At 14 days after application of herbicide, the number total leaves, number of dead leaves, number of tillers, fresh weight of commercial leaf and root length.

Doses subletais de glifosato em combinação com manganês foliar na produção de capim marandu

A deriva do herbicida glifosato pode estimular crescimento e/ou rendimento produtivo em plantas não-alvo, caracterizando efeito hormese. Ainda, manifesta-se amarelecimento momentâneo em folhas novas, característico de deficiência nutricional. Deste modo, o trabalho teve por objetivo avaliar o efeito hormese por aplicação de glifosato em Urochloa brizantha cv. Marandu. Foi avaliada a resposta produtiva aérea (PMS) e radicular (MSR) da forrageira por aplicação foliar de sete doses subletais do equivalente ácido (e.a.) de glifosato (5,40, 10,80, 21,60, 43,20, 64,80, 86,40 e 108,00, g e.a. ha-1) e controle, sob ausência e presença de manganês (1000 g ha-1) à calda de pulverização, em quatro colheitas sequenciais, caracterizando esquema fatorial 8 x 2 x 4, com quatro repetições. As doses subletais de glifosato com adição de manganês à calda de pulverização reduziram o efeito herbicida, com persistência de PMS durante período experimental (4 cortes). Para doses sem adição de manganês à calda de pulverização, houve falência produtiva nos cortes 2, 3 e 4, para doses 86,40 e 108,00 g e.a. ha-1. A presença de manganês à calda de pulverização assegurou massa seca de raiz superior àquelas sem adição de manganês, sendo constatado efeito do herbicida nas doses igual e superiores a 43,60 g e.a. ha-1.

Drift Distance in Aircraft Glyphosate Application Using Rice Plants as Indicators

ABSTRACT: This study aimed to evaluate the potential for glyphosate drift during aerial application using rice plants as sentinels, aiming to determine the effect of drift on irrigated rice crops. For this purpose, a field experiment was performed using an entirely randomized design with four replicates, evaluating different distances from the site of application [control (no application), 0, 12.5, 25, 50, 75, 100, 150, 200, 300, and 400 m]. The experiment was carried out at the Granjas 4 Irmãos farm, located in the Rio Grande city, Rio Grande do Sul State, Brazil. The glyphosate dose application was 1,920 g e.a. ha-1 (Roundup Transorb®, 480 g e.a. L-1 glyphosate isopropylamine salt). A dose-response curve was developed to estimate the drift rate in sentinel plants, by applying increasing glyphosate doses in rice plants and assessing the injury level. The drift rates estimated by the injury level in sentinel plants were 14% (150 m), 13% (200 m), and 5% (400 m). Death of the experimental units was observed for distances between 0 and 50 m, while in distances between 75 and 150 m, 25 to 50% of the plants survived, reducing productivity. In the distances between 200 and 400 m, there was no reduction in productivity when compared to the control, even when the injury levels reached 52 to 82%. Thus, we concluded that a 5% glyphosate drift reached up to 400 m from the application range. Considering the recommendation of zero drift, distances greater than 400 m should be adopted to avoid symptoms in rice plants. We suggest using distances of more than 400 m in future studies.

Use of foliar fertilizers as attenuators of injuries caused by glyphosate drift in young coffee plantations

Glyphosate is the most used product for weed control in young coffee planting rows. The application is carried out in a directed way, avoiding the contact of the product with the crop. However, drift and consequent plant injuries frequently occur. An alternative to reduce these injuries is the use of attenuators capable of reducing the negative effects caused by this herbicide. Therefore, the objective of this study is to verify the efficiency of foliar fertilizers (Fertiactyl Pos® and Crop+) as attenuators of the toxic effects caused by the use of glyphosate in the coffee crop. Thus, coffee seedlings were subjected to different doses of the mixture of Fertiactyl Pos® with glyphosate and Crop+ with glyphosate. The treatments were applied on top of the plants. The percentage of coffee intoxication was evaluated at 14, 21, 28, 35, 42 and 70 days after application. At 90 days after application, height, leaf area and shoot and root dry matter were evaluated. Higher doses of glyphosate (1440 and 2880 g ha-1) without the use of attenuators caused intoxication levels close to 80% at 28 and 90 DAA. The use of Fertiactyl Pos® and Crop+ reduced the injuries caused by the application of glyphosate, regardless of the dose of herbicide and fertilizers, but with different levels of action. All the morphological variables measured suffered a negative action with the isolated use of glyphosate, with a tendency to recover when the attenuators were applied. It is concluded that the two attenuators were efficient in suppressing the deleterious effects of glyphosate on coffee plants affected by this herbicide. However, the attenuator Crop+ showed better recovery results. For 720 g ha-1 of glyphosate, the dose most used in the field, 8 L ha-1 is recommended for Fertiactyl Pos® and 4 L ha-1 for Crop+. Key words: Coffea arabica; Crop+; Fertiactyl Pos®; Injury; Weed control.