Application Of Glyphosate Herbicide Research Articles

Biology of the invasive species Eragrostis plana in Southern Brazil: What have we learned and how may this help us manage it?

AbstractSince its accidental introduction in 1951, the South African species Eragrostis plana has invaded a large part of the Pampa biome in South America, a highly diverse grassland ecosystem that has coexisted with livestock since its introduction at the beginning of the 17th century. E. plana, a perennial tussock grass with a deep and abundant root system, is resistant to frost and cattle grazing, and a successful competitor for environmental resources. The species is diploid, C4 dispersed endozoochorically, and flowers in late spring and early summer, with optimal germination occurring at 35°C and viability up to 39–40°C. It is allelopathic because it produces several phenols and alkaloids. Extreme soil disturbance or intense grazing favours initial invasion. Nonetheless, grazing exclusion enhances E. plana competition and affects the grassland community and diversity. E. plana is highly tolerant to interspecific competition, especially with grasses exhibiting a similar growth habit. Under water stress, it responds faster by increasing its root system by 66% more than native grass. Moreover, antioxidant system activity increases, and the species recovers quickly through osmolyte production. In non‐invaded fields, avoiding soil disturbance and intensive grazing are key strategies to preserving Biome Pampa. Nonetheless, in fields where the invasion has already occurred, grazing must be maintained, cattle quarantined practiced, along with strategies that reduce cover and prevent the spread of E. plana. Liming and fertilising native grasslands improve their potential to compete with E. plana. The wiper applicator, a device that allows glyphosate herbicide application selectively to E. plana, is an important component of the integrated weed management system, especially with very severe infestations. Establishing strategies to contain or manage E. plana should be a priority to preserve the biodiversity of the Pampa. In the future, innovative options could also help prevent new invasions.

Efikasi Herbisida Isopropilamina Glifosat 480 g/l pada Gulma Persiapan Tanam dan Pengaruhnya terhadap Tanaman Serta Hasil Padi Sawah Tanpa Olah Tanah

One of the efforts to control weeds in preparing land for lowland rice cultivation with the No-Tillage system one of which uses isopropylamineglyphosate herbicide. The purpose of this study was to determine the dose of glyphosate herbicide that effectively controls weeds for preparation of lowland rice planting with the no tillage system, to determine changes in weed composition in lowland rice after the application of glyphosate herbicide, and to determine the effect of the no tillage system after the application of glyphosate herbicide on growth and paddy yields. Data collection was carried out from June to September 2022 in the rice fields of Trimurjo District, Central Lampung Regency and the Weed Science Laboratory, Faculty of Agriculture, University of Lampung. The treatment was arranged using a randomized block design with 4 replications and 6 treatments consisting of the glyphosate herbicide doses (1,080; 1,440; 1,800; 2,160 g/ha) + no tillage, manual weeding, and intensive tillage system. Homogeneity of variance was tested by Barlett's test and then analyzed for variance. Separation of the mean was carried out using the least significant difference test (LSD) at the 5% level. The results showed that the herbicide isopropylamine glyphosate doses of 1,800 and 2,160 g/ha of the no tillage system could be used to replace the intensive tillage system because it was effective in controlling total weeds, sedges, grasses, and broad leaf groups, dominant weed Fimbristylis miliacea, Echinochloa colonum, Ludwigia octovalvis and Monochoria vaginalis up to 6 WAP, causing a change in the composition of weed species from Echinochloa colonum become monochoria vaginalis at 3 WAP, and from Echinochloa colonum become Ludwigia octovalvis at 6 WAP. The growth is not stunted and yield of lowland rice plants is equivalent to the intensive tillage system with grain yields per hectare of 5.14 - 5.49 t/ha. Key words : weeds, isopropylamine glyphosate, paddy field, no tillage

Nitrogen Fertilization and Glyphosate as a Growth Regulator: Effects on the Nutritional Efficiency and Nutrient Balance in Emerald Grass

Nitrogen (N) is one of the promising nutrients for lawn growth and is required for the lawn’s proper growth and development, but it also increases mowing frequency. Glyphosate herbicide application in sub-doses, as a growth regulator, can reduce the maintenance costs without any adverse reduction in the density and nutritional status of grasses. The objective of this study was to evaluate the influences of nitrogen and glyphosate doses on the growth, aesthetic quality and nutritional status of emerald grass (Zoysia japonica Steud.). The experiment was conducted at the Research and Extension Education Farm of São Paulo State University (UNESP), Ilha Solteira, SP, Brazil, in an Ultisol. The experiment was designed as a randomized block with 12 treatments arranged in a 3 × 4 factorial scheme with 4 replications, comprised of a control (without N), 15 and 30 g N m−2 of urea, applied in five splits annually, and glyphosate doses (0, 200, 400 and 600 g ha−1 of the active ingredient, a.i.). The split N fertilization at the rate of 15 g m−2 and glyphosate at the dose of 400 g ha−1 maintained nutritional status of emerald grass. Nitrogen at the rate 15 g N m−2 (in five splits per year) was observed to produce lower growth traits, an adequate aesthetic quality and longer stability of the nutrients in emerald grasses through lower exportation, with removal of “clipping” after mowing. In addition, glyphosate, at the dose of 400 g a.i. ha−1, was efficient in reducing the leaf area, plant height, shoot dry matter and total dry matter by 18.3, 14.7, 6.8 and 8.1%, respectively, as compared to the control. However, this dose did not impair the coloration and resulted in a lower exportation of nutrients by reducing the need to replenish by fertilization. Therefore, fertilization with 15 g N m−2, associated with application of 400 g a.i. ha−1 of glyphosate, is recommended for emerald grass in the tropical savannah of Brazil.

Can mulch be effective in controlling exotic grasses and promoting natural regeneration in ecological restoration?

Mulching use in agriculture has been known since 1802 as the practice of spreading dry leaves and straw on the soil to prevent erosion and water loss. Our study evaluated the mulch effectiveness in the establishment of regenerating seedlings and its contribution to the control of exotic grasses. The studies were carried out in an ecological restoration area in the municipality of Itapira-SP. The treatment with mulching consisted in chemical desiccation with glyphosate herbicide application, keeping the dry grass on the ground. In the control treatment, after chemical weeding, the grass was removed with manual mowing, exposing the soil. Eight months after implantation, we sampled all regenerating seedlings in 100 plots of 50 x 50 cm in each treatment. We considered as seedlings all individuals of tree species less than 100 cm tall. We calculated richness, abundance, similarity, and the relationship of the frequency of seedlings to the height of the mulch. We sampled eight species with 42 seedlings, with only one not identified. The highest abundance and species richness were found in the treatment with mulch (n = 34 individuals; eight species), the most abundant being Schinus terebinthifolia Raddi (14 individuals) followed by Solanum mauritianum Scop. (11 individuals), and Platypodium elegans Vog. (three individuals). The presence of exotic grasses was lower in the plots of the mulching (13%) compared to the control treatment (67%). The highest frequency of seedlings was obtained with mulch height from 21 to 37 cm. We suggest that adaptive management practices, such as the use of the mulching technique, can be implemented in ecological restoration areas, because they favor the natural regeneration of native seedlings and can contribute to the control of exotic grasses, but the height of the layer must be controlled.

Effects of glyphosate plus foliar manganese application on the production and quality of marandu grass

In this study, the stimulatory effects of application of glyphosate herbicide coupled with manganese sulfate (8%) foliar fertilizer on the production and bromatological characteristics of Brachiaria brizantha ‘Marandu’ were evaluated. The experiments were performed using randomized complete block design with a 5×4 factorial scheme in plots subdivided over time (across four evaluations) with four repetitions, totaling 100 observations. The effects of sublethal doses of acid equivalent (a.e.) of glyphosate (5.40, 21.60, 64.80, and 108.00 g·a.e.·ha-1) and control plus manganese sulfate foliar fertilizer (1,000 g ha-1) were assessed in four successive evaluations at a defoliation frequency of 21 days. Foliage at 20 cm height (to evaluate forage production); leaf/stem ratio (LSR); and contents of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin (LIG) were measured in experimental plots with a usable area of 7.5 m2. Application of sublethal doses of glyphosate plus manganese sulfate did not increase forage production, increased LSR, reduced LIG content, and did not affect CP content in all four evaluations. NFD and ADF indicated satisfactory qualitative indices for animal feed following the application of sublethal doses of glyphosate plus manganese sulfate in all four evaluations.

Selective herbicide control: using furrows and carbon seed coatings to establish a native bunchgrass while reducing cheatgrass cover

Invasion by exotic grasses is degrading dryland ecosystems worldwide and efforts to restore native vegetation in invaded areas have been largely unsuccessful. Control of invasive grasses with herbicide also limits restoration efforts using native seed. In this study, we evaluated two approaches that could allow for the restoration of a native species Pseudoroegneria spicata while reducing an invasive annual grass Bromus tectorum with a herbicide mixture in the sagebrush steppe ecosystem (the United States). We used two methods to protect native seeds from herbicide: activated carbon was applied as a seed coating with the intent of absorbing the herbicide around the seed, and furrows were used to side‐sweep soil sprayed with herbicide away from the planted seed. Our results indicate that imazapic + glyphosate herbicide application had a strong negative effect on the invasive annual grass, reducing B. tectorum cover 91% after 1 year, and 39% after 2 years. Herbicide also had strong negative effects on P. spicata without a carbon‐coating or furrow treatment, reducing seedling emergence 38%, 2‐year plant density 65%, and 2‐year total growth 90%. Both activated carbon seed coatings and furrow treatments limited herbicide effects on P. spicata 2‐year growth, but neither treatment alone mitigated herbicide effects on all life stages. Combining carbon coatings and furrow treatments mitigated harmful herbicide effects on several plant stages (seedling emergence, plant densities, and growth). Our results suggest that combining activated carbon coatings and furrow results in similar establishment of a native perennial as a non‐herbicide seeding and lowers B. tectorum abundance.

Levantamento de plantas daninhas em lavoura de soja irrigado com pivô em Cachoeira do Sul - RS

The presence of weed species in soybean crops is a concern for farmers. Knowing these species is of great importance, as they cause serious damage to crops due to competition for nutrients, water, light and physical space with soy. This work aimed to survey weeds in pivot irrigated soybean crops in Cachoeira do Sul municipality, Capané district, in the experimental area of the Rio Grandense do Arroz Institute (IRGA). The evaluations were performed by applying the 0.25 m2 square method, launched at random sixty times. Weeds in the sampled areas were removed from the soil, species identified and quantified. Evaluations were performed after three applications of glyphosate herbicide. Even after glyphosate applications, seven species were identified, representing the families Asteraceae, Poaceae, Malvaceae, Euphorbiaceae and Rubiaceae. This survey enables the planning of preventive strategies for the sustainable control of weeds in the field, reducing production costs and the impact on the environment.

Grasses Control Strategies in Setting Restoration Stand of the Atlantic Forest

This study aimed to assess the effectiveness of four weed control strategies in forest setting stands linked by a set of Atlantic Forest tree species. Four treatments were employed: mechanical ? manual hoeing and mowing; chemical ? glyphosate herbicide application in the total area; chemical ? cultural ? herbicide spraying and herbaceous legume intercropping; chemical-mechanical ? herbicide planting in rows and mowing in the interrows. Diameter, crown area and soil cover percentage of the eight tree species were assessed at 18 months. Herbicide spraying in total area promoted the greatest reduction in weed populations, as well as superior growth in height, diameter, crown area and soil cover of the tree species. More interventions were necessary in the treatment of mechanical weed control that has also shown the least growth of the tree species. The chemical method was the most effective in weed control and promoted the greatest growth of the tree specie

Preliminary Environmental Risk Assessment of Genetically Modified Oilseed Rape MON 88302 for Food and Feed Uses, Import and Processing under Regulation (EC) No 1829/2003 (Application EFSA/GMO/BE/2011/101)

Preliminary Environmental Risk Assessment of Genetically Modified Oilseed Rape MON 88302 for Food and Feed Uses, Import and Processing under Regulation (EC) No 1829/2003 (Application EFSA/GMO/BE/2011/101)

The Effect of Glyphosate Harbicide on Soil Fungi

Glyphosate herbicide is one of the herbicide used throughout the world and they are very important to agriculture. Despite the role of glyphosate herbicide to agriculture, they also posed direct or indirect threats to the health of humans and also to the nature and survival of soil microorganisms. This study was carried out to determine the effect of glyphosate herbicide on soil fungi. Enumeration of fungal population in the soil samples before and after treatment was carried out. The fungal count was found to be 2.8x103cfu/g before the treatment with glyphosate herbicide and the number continue to decrease up to 0.4x103cfu/g in the 15day of glyphosate herbicide treatment. The fungal population decreased upon treatment with glyphosate herbicide when compared to the control i.e. the untreated soil sample. Glyphosate herbicide causes greater reduction in fungal count because the fungal populations decreased gradually and complete disappearance of some species after 6 days of treatment and continue to decrease up to 15 days after treatment. Soil fungi were isolated from the soil before the application of glyphosate herbicide; they include A. niger, A. flavus, Penicillium spp., Microsporium spp. Trychophyton spp. upon application of glyphosate herbicide, not all the fungi isolated before treatment survive the effect of glyphosate herbicide. The most frequently isolated fungi that survive up to 15 days of treatment is Aspergillus species (A. flavus and A. niger) while Microsporium spp., Trychophyton spp. and Penicillium spp. disappeared completely after 9 days of treatment.

Effects of management by glyphosate or tillage on the weed vegetation in a field experiment

Glyphosate herbicides play a prominent role internationally in weed management due to their broad spectrum effectiveness. There are concerns that a high reliance on glyphosate herbicides will negatively affect biodiversity over time. In Europe, where cropping systems are carried out without glyphosate resistant crops (GMO), glyphosate herbicides are applied between cropping seasons either in combination with or in place of plowing. We explored the effects of mouldboard plowing, chisel plowing, and glyphosate herbicide application (in a dose reflecting 100% of the manufacturer’s recommendation and a dose reflecting 50%) on weed species number, density, true diversity and community composition. The field experiment was conducted for three consecutive years in a randomized plot design on a naturally occuring weed community without a crop.A total of 83 species and 4 genus were identified over the three years of surveying. By applying a Multinomial Species Classification to the dataset, it was determined that root and rhizome propagating species as well as annual agricultural weeds with no pronounced seasonality in their germination were rarer on glyphosate treated plots than on tillaged plots. Promoted by glyphosate application were in particular grassland legumes and hemicryptophytes. Partial Redundancy Analyses (pRDA) showed that the species communities evolved over the years with dependency on the type of treatment and timing of the treatments. The overall average number of species was 19.7/m2 and the true diversity was 8.3/m2. The average density was 295 plants/m2. In all of the treatments, a factorial ANOVA demonstrated that species numbers and true diversity sank in all three of the years of the experiment over the course of the vegetation period whereas the density tended to rise.The reality of weed management is that any method employed will influence the weed composition in some way. Our experiment demonstrated that some species will be favored over others depending on the weed management method, but the overall biodiversity of the weed community was not more negatively affected by one method compared to another.

Plant Community Diversity and Tree Growth Following Single and Repeated Glyphosate Herbicide Applications to a White Spruce Plantation

Glyphosate herbicide is widely used to control bluejoint reedgrass (Calamagrostis canadensis (Michx.) Beauv.), trembling aspen (Populus tremuloides Michx.), and other competing species in regenerating white spruce (Picea glauca (Moench) Voss) plantations in Alberta, Canada. In 2004, we initiated a study to examine the effects of the aerial application of glyphosate herbicide on plant community diversity and tree growth near Calling Lake, Alberta. Four treatments were applied: (a) no treatment (control); (b) herbicide application in the first growing season after harvesting; (c) herbicide application in the third growing season after harvesting; and (d) herbicide application in the second and fourth growing seasons after harvesting (two treatments). After 11 growing seasons, species richness was not significantly affected by treatment, while Shannon and Simpson index values were highest in areas treated with herbicide in the first growing season. Herbicide treatment did not have a significant effect on the cover of bluejoint reedgrass after 11 growing seasons, but did significantly reduce trembling aspen and paper birch cover and height. Application of glyphosate in the second and fourth growing seasons resulted in the greatest reductions to aspen cover and height, as well as significant increases in spruce diameter at age 11. Simulations with the Mixedwood Growth Model indicate that all tested herbicide treatments will reduce aspen volume while increasing spruce volume at age 90, with the largest impacts evident where two treatments were applied.

Seasonal Influence of Glyphosate Herbicide Application on Soil Bacteria in Benue State, North Central, Nigeria

Seasonal Influence of Glyphosate Herbicide Application on Soil Bacteria in Benue State, North Central, Nigeria

Re‐vegetation with native species does not control the invasive Ruellia simplex in a floodplain forest in Florida, USA

AbstractQuestionPlanting or seeding native species after control of invasive species can limit re‐invasion and hasten establishment of native species. Ruellia simplex (Mexican petunia) invades floodplain forests in Florida, and is controlled with glyphosate herbicide. Will herbicide application used to control this weed allow establishment of native vegetation and limit R. simplex?LocationFloodplain forest altered by stormwater run‐off, Lake Jesup Conservation Area, Sanford, FL, US.MethodsWe evaluated re‐vegetation following herbicide application to control R. simplex. For re‐vegetation, we planted or seeded native species (Andropogon glomeratus, Juncus effusus, Panicum longifolium, Solidago fistulosa) and measured stem density, percentage cover, above‐ground biomass and species richness for 1 yr. We compared the results to those from control plots (i.e. no herbicide, no re‐vegetation) and plots where R. simplex was sprayed with herbicide but not planted or seeded with native species.ResultsUnassisted re‐colonization (i.e. plots where R. simplex was sprayed but not planted or seeded with native species) did not result in native plant restoration. Re‐vegetation treatments (i.e. plots where R. simplex was sprayed and planted or seeded with native species) did not restore native vegetation; nor did re‐vegetation treatments reduce R. simplex stem density, percentage cover or biomass compared to control plots. However, total species richness, including native and exotic species richness, increased in plots planted with a native plug mix compared to control plots (i.e. no herbicide, no re‐vegetation). Native species failed to germinate in all seeding treatments. Plugs had adequate survival (2–57% depending on species) but did not prevent re‐invasion of R. simplex. Re‐invasion of R. simplex occurred in plots despite application of glyphosate herbicide and re‐vegetation treatments.ConclusionsRe‐vegetation by seeding or planting did not establish native vegetation in the first year, instead, R. simplex reinvaded. Abiotic and biotic site conditions, e.g. invasive species propagule pressure and altered soil nutrients, may have limited seed germination and survival of planted seedlings. More research is necessary to determine if a reduction in invasive species propagules through repeated herbicide application coupled with planting native species results in native plant restoration in the longer term.

Degradation Dynamics of Glyphosate in Different Types of Citrus Orchard Soils in China

Glyphosate formulations that are used as a broad-spectrum systemic herbicide have been widely applied in agriculture, causing increasing concerns about residues in soils. In this study, the degradation dynamics of glyphosate in different types of citrus orchard soils in China were evaluated under field conditions. Glyphosate soluble powder and aqueous solution were applied at 3000 and 5040 g active ingredient/hm2, respectively, in citrus orchard soils, and periodically drawn soil samples were analyzed by high performance liquid chromatography. The results showed that the amount of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in soils was reduced with the increase of time after application of glyphosate formulations. Indeed, the amount of glyphosate in red soil from Hunan and Zhejiang Province, and clay soil from Guangxi Province varied from 0.13 to 0.91 µg/g at 42 days after application of aqueous solution. Furthermore, the amount of glyphosate in medium loam from Zhejiang and Guangdong Province, and brown loam from Guizhou Province varied from less than 0.10 to 0.14 µg/g, while the amount of AMPA varied from less than 0.10 to 0.99 µg/g at 42 days after application of soluble powder. Overall, these findings demonstrated that the degradation dynamics of glyphosate aqueous solution and soluble powder as well as AMPA depend on the physicochemical properties of the applied soils, in particular soil pH, which should be carefully considered in the application of glyphosate herbicide.

Comparison of broiler performance and carcass yields when fed diets containing genetically modified canola meal from event DP-Ø73496-4, near-isogenic canola meal, or commercial canola meals

Genetically modified (GM) canola (Brassica napus L.) line containing event DP-Ø73496–4 (hereafter referred to as 73496 canola) was produced by the insertion of the glyphosate acetyltransferase (gat 4621) gene derived from Bacillus licheniformis. Expression of the GAT4621 protein present in 73496 canola plants confers in planta tolerance to the herbicidal active ingredient glyphosate. The objective of this study was to compare the nutritional performance of broiler chickens fed canola meal from 73496 canola seed with that of broiler chickens fed non-GM canola meal in a 42-d feeding trial. Diets were prepared using meal processed from seed from unsprayed 73496 plants or from plants sprayed with an in-field application of glyphosate herbicide [73496(S)]. For comparison, additional diets were produced with canola meal obtained from the non-GM near-isogenic control or non-GM commercial reference DuPont Pioneer brand varieties 42H72, 42H73, 46A65, and 44A89. Diets were fed to Ross 708 broilers (n = 120/group, 50% male and 50% female) in 3 phases: starter and grower phases containing 10 or 20% canola meal, respectively, and a finisher phase with a common corn-soybean meal diet without any canola meal. No statistically significant differences were observed in growth performance measures or organ and carcass yields between broilers consuming diets produced with canola meal from unsprayed or sprayed 73496 seed and those consuming diets produced with canola meal from control seed. Additionally, all performance, organ, and carcass measures from control, 73496, and 73496(S) canola treatment groups were within tolerance intervals constructed using data from the reference canola groups. It was concluded from these results that meal processed from 73496 canola seed (unsprayed plants or plants sprayed with glyphosate) was nutritionally equivalent to meal processed from non-GM near-isogenic control canola seed.

Associações entre glifosato e herbicidas pós-emergentes para o controle de trapoeraba em soja RR®

Este trabalho teve o objetivo de avaliar a seletividade e a eficácia da associação do glifosato com herbicidas pós-emergentes no controle de trapoeraba na cultura da soja Roundup Ready®. Para tanto, o experimento foi instalado no delineamento de blocos ao caso, com quatro repetições, onde os tratamentos foram constituídos de quatro doses do herbicida cloransulam-metil (10, 20, 30 e 40 g ha-1), quatro doses do herbicida clorimurom-etílico (2,5, 5,0, 7,5 e 10,0 g ha-1), imazetapir a 100 g ha-1 e lactofen a 72 g ha-1, todos estes utilizados em associação com o herbicida glifosato a 960 g ha-1. Também foram incluídas três testemunhas, sendo aplicação única do herbicida glifosato a 960 g ha-1, aplicação sequencial do glifosato a 960/ 960 g ha-1 e testemunha geral sem capina. Os resultados demonstraram que apenas a aplicação única do herbicida glifosato a 960 g ha-1 e sua associação com as menores doses de cloransulam-metil (10 g ha-1) e clorimurom-etílico (2,5 g ha-1) não proporcionaram controle efetivo da trapoeraba. Todos os tratamentos herbicidas não influenciaram na produtividade da soja RR®, embora a associação do glifosato com a maior dose de clorimurom-etílico (10 g ha-1) tenha proporcionado redução significativa no peso de 1000 grãos de soja.

Evaluation of glyphosate application in regulating the reproduction of riparian black locust (Robinia pseudoacacia L.) after clear-cutting, and the possibility of leaching into soil

Black locust (Robinia pseudoacacia L.)—an invasive alien species in riparian forests—is becoming more prevalent in many rivers of eastern Japan. Riparian black locust forests are typically cut down to maintain river-flow capacity. However, such forests often reproduce rapidly by stump sprouting and root suckering and regenerate by germination. Thus, more effective riparian forest management approaches are required. To regulate the reproduction of black locust forests after clear-cutting, we examined the regrowth-inhibiting effects of glyphosate herbicide application to stumps, in accordance with current river management protocol (i.e., winter logging operation). Further, we investigated the concentrations of glyphosate leaching into the soil at a depth of 30 cm in a riparian area of the Tenryu River. Our results showed that glyphosate application to stumps completely inhibited stump sprouting but not root suckering or seedling germination. The glyphosate concentration leaching into the soil reached a maximum (2.6 ± 0.7 mg kg−1, mean ± standard error) on day 1 after the application, and subsequently declined to below the detection limit on day 2. Thus, the rapid degradation of glyphosate was confirmed, despite the fact that the herbicide leached into the soil after application to the stumps. The glyphosate application has limited effectiveness against root suckering and germination of riparian black locust forests after clear-cutting in winter, in accordance with the current river management protocol.

Effects of soil-borne Rhizoctonia solani on canola seedlings after application of glyphosate herbicide

Rashid, A., Hwang, S. F., Ahmed, H. U., Turnbull, G. D., Strelkov, S. E. and Gossen, B. D. 2013. Effects of soil-borne Rhizoctonia solani on canola seedlings after application of glyphosate herbicide. Can. J. Plant Sci. 93: 97–107. Application of glyphosate (N-phosphonomethyl glycine) prior to seeding is a common weed management practice in many agricultural systems. However, there are concerns that this practice may increase the impact of soil-borne diseases on the crop, even in cultivars that are resistant to glyphosate. In the current study, the effects of pre-plant applications of glyphosate on seedling blight of canola caused by Rhizoctonia solani and subsequent crop growth were examined under field and greenhouse conditions. Under greenhouse conditions in soil inoculated with R. solani, glyphosate application 15 d before seeding reduced seedling emergence, increased damping-off, and decreased plant height and shoot dry weight of canola relative to a glyphosate-free control. However, the adverse effects were substantially reduced when the crop was seeded 33 d after glyphosate application. This indicates that glyphosate application prior to planting may increase the impact of R. solani on canola seedlings, but that this effect diminishes quite rapidly. Soil populations of R. solani declined over the 33-d period regardless of glyphosate treatment. Glyphosate application 10 d before seeding increased seedling emergence and seed yield (1 of 2 yr) of canola in field trials inoculated with R. solani.

Teratogenic Effects of Glyphosate-Based Herbicides: Divergence of Regulatory Decisions from Scientific Evidence

The publication of a study in 2010, showing that a glyphosate herbicide formulation and glyphosate alone caused malformations in the embryos of Xenopus laevis and chickens through disruption of the retinoic acid signalling pathway, caused scientific and regulatory controversy. Debate centred on the effects of the production and consumption of genetically modified Roundup Ready ® soy, which is engineered to tolerate applications of glyphosate herbicide. The study, along with others indicating teratogenic and reproductive effects from glyphosate herbicide exposure, was rebutted by the German Federal Office for Consumer Protection and Food Safety, BVL, as well as in industry-sponsored papers. These rebuttals relied partly on unpublished industry-sponsored studies commissioned for regulatory purposes, which, it was claimed, showed that glyphosate is not a teratogen or reproductive toxin. However, examination of the German authorities' draft assessment report on the industry studies, which underlies glyphosate's EU authorisation, revealed further evidence of glyphosate's teratogenicity. Many of the malformations found were of the type defined in the scientific literature as associated with retinoic acid teratogenesis. Nevertheless, the German and EU authorities minimized these findings in their assessment and set a potentially unsafe acceptable daily intake (ADI) level for glyphosate. This paper reviews the evidence on the teratogenicity and reproductive toxicity of glyphosate herbicides and concludes that a new and transparent risk assessment needs to be conducted. The new risk assessment must take into account all the data on the toxicity of glyphosate and its commercial formulations, including data generated by independent scientists and published in the peer-reviewed scientific literature, as well as the industry-sponsored studies.