Herbicide Research Articles

Field Bindweed (Convolvulus arvensis) Control in Tef (Eragrostis tef (Zucc.) Trotter) through Various Herbicide Combinations

Field bindweed is the major weed problem for tef producers across the central highlands of Ethiopia. Herbicide application alone or coupled with once or twice hand weeding for field bindweed control is difficult due to its biological features, labor-intensive, and time-consuming. The field trial was carried out at Debre Zeit from 2020 to 2021 cropping seasons to investigate different postemergence herbicides against the grass and broadleaf weeds, in general, and field bindweed in particular, in tef farming, using a randomized complete block design with three replications. As a result, we could see that the herbicide combination had no visible effect on durum wheat’s overall performance, which makes us recommend it for the control of field bindweed. In the sequential application, a wide spectrum of herbicides (Musket Power OD 460, Pallas 45 OD, and Sekator OD 375) were applied at tillering stage, and other selective herbicides (Derby 175 SC and 2,4-diamine salt 720 g/L 720 g/L) were applied at the heading stage, and the last nonselective herbicide (Roundup) was applied at physiological maturity of tef when the Convolvulus arvensis was regrowth naturally/latecomer weed. All postemergency herbicide treatments reduced significantly both broadleaf and grass weeds, in general, and C. arvensis infestation, in particular, when compared to the weedy control. Of these, Musket Power OD 460 at tillering stage integrated with 2,4-diamine salt 720 g/L at the heading stage was more effective than other herbicides for eliminating all weeds and C. arvensis in particular throughout the crop life. This weed management option resulted in considerably enhanced weed control efficiency and weed killing potential, reduced weed dry biomass and yield loss, improved grain yield, and economic benefit with an acceptable marginal rate of return for tef growers.

Validation of gas chromatography mass spectrometry (GC-MS) qualitative method for detection of paraquat in postmortem samples by sodium borohydride-platinum chloride chemical reduction

To develop a GC-MS method for the detection of paraquat by sodium borohydride-platinum chloride reduction in postmortem samples. Paraquat [1,1′-dimethyl-4,4′-bipyridilium dichloride,(PQ)] is a bipyridylium quaternary ammonium contact herbicide. At the Institute of Forensic Science and Legal Medicine (IFSLM), an average of 13 cases of PQ poisoning are submitted annually for postmortem toxicological analysis. Previously a colorimetric method for the identification of PQ was used. A more sensitive method was needed to confirm the presence of PQ. There is limited studies on liquid-liquid extraction (LLE) of postmortem fluids and tissues for determination of PQ by GC-MS. Some methods used a chemical reduction involving sodium borohydride (NaBH4) or sodium borohydride with nickel chloride (NaBH4-NiCl2), prior to LLE, to gain more volatile compounds for analysis. In the absence of NiCl2, platinum (IV) chloride (PtCl4) was used as a substitute catalyst in the validation. The aim of this validation is to identify PQ in suspected poisoning cases from postmortem samples using chemical reduction reaction, followed by LLE and then (GC-MS). The qualitative method involved an initial chemical reduction of PQ to the perhydrogenated product and monoene by-product: 500 μL blood, urine or tissue homogenate was placed in a glass tube, followed by 200 μL toluene, 400 μL PtCl4 (1% w/v) and then 500 μL NaBH4 (40% w/v) was added dropwise. The mixture was vortexed then left to stand for 1½ hours at room temperature. 1 mL 5 N sodium hydroxide solution was added to stop the reaction. For LLE, 3 mL hexane: ethyl acetate (4:1) was added to the tube and placed on shaker for 45 minutes at 300 rpm. The sample was centrifuged for 1 hour at 1400 g. The hexane:ethyl acetate layer was then transferred to a beaker and allowed to evaporate to dryness. The residue was reconstituted with 1 mL hexane, transferred to GC vial, and allowed to evaporate to dryness. The residue was then reconstituted with 100 μL hexane, and transferred to a GC vial fitted with glass insert, with 1 μL being injected into the GC-MS system (Agilent 7890A GC coupled with an Agilent 5975C VL MSD with Triple Axis Detector Mass Spectrometer). As recommended by the Scientific Working Group for Forensic Toxicology (SWGTOX), the validation parameters for qualitative confirmation/identification were specificity, recovery, carryover, repeatability and limit of detection. The method was applied to blank blood and urine samples, spiked blood and urine samples, as well as 10 suspected PQ poisoning cases (24 postmortem samples) submitted to the IFSLM. The blank blood and urine samples analysed did not yield any positive results for the analytes of interest. Blood and urine samples spiked with the PQ standard solution resulted in the detection of both the perhydrogenated product and monoene by-product. The limit of detection for both reduction products was 30 ppm. There was no detection of the analytes in the three blanks analysed after an injection of 1000 ppm PQ. The reduction products of PQ were detected in all 10 cases. Four of these cases had previously given negative results using the colorimetric test. The PtCl4 was found to be an adequate substitute catalyst in the reduction procedure. The procedure was proven to be sensitive, repeatable and robust. All sample types assessed by the method gave positive results, however stomach and content produced the best chromatograms with sharp, clearly defined and resolved peaks. In summary, the presented procedure provided excellent performance in the identification of the reduction products of PQ in postmortem samples.

Hepatocellular Recovery of Chronic Paraquat Induced Liver Toxicity in Vitamin E and C Treated Male Wistar Rats

Paraquat is an organic compound also known as methyl viologen, a chemical herbicide or weed killer with highly toxic effect on ingestion or exposure. Vitamin E and C are powerful antioxidants that act as initial responder against oxygen reactive species called free radicals which attack and destroy the tissues. The aim of this study was to determine a short term therapeutic effect of vitamin E and C combination on liver enzymes parameters of paraquat induced liver toxicity in male albino rats. 200 male albino rats were used for the study. The 200 rats were divided into four main groups (A, B, C, D) consisting of 50 rats in each group. The Groups were further divided into two subgroups having 25 rats in each subgroup. “A” group was not induced with paraquat while “B”, ‘C” and “D” groups were induced with increasing dose of 0.02g, 0.04g and 0.06g of paraquat respectively. “A” group had two subgroups; “Ao” and “AVEC” which represented the sub-group not treated with Vit E and the subgroup treated with Vit E (500mg) respectively. This also applied to group “B”, “C” and “D” paraquat was administered every forth night followed by treatment with the vitamins for one month. Blood samples were collected and analysed for liver function (SGOT, SGPT, ALT And GGT). There was a significant increase in the level of the liver enzymes among the “Ao”, “Bo”, “Co” and “Do”, p-value<0.05 and also among the “AVEC”, “BVEC”, “CVEC” and “DVEC”, p-value<0.05. The result also showed that there were significant differences in intra-group comparison in all the liver enzyme parameters, p-value<0.05 while there was no significant difference among the AO and AVEC subgroups for all parameters. This study has shown that vitamin E and C combination has a therapeutic effect in male albino rats on one month of weekly treatment. Therefore, a weekly treatment with Vit E and C may treat liver disease toxicity associated with paraquat toxicity in rats.

Old World Vultures Reflect Effects of Environmental Pollutants Through Human Encroachment.

African wildlife face challenges from many stressors including current and emerging contaminants, habitat and resource loss, poaching, intentional and unintentional poisoning, and climate-related environmental change. The plight of African vultures exemplifies these challenges due to environmental contaminants and other stressors acting on individuals and populations that are already threatened or endangered. Many of these threats emanate from increasing human population size and settlement density, habitat loss from changing land use for agriculture, residential areas, and industry, and climate-related changes in resource availability. Environmental chemicals that are hazardous include legacy chemicals, emerging chemicals of concern, and high-volume-use chemicals that are employed as weed killers and in other agricultural applications. Furthermore, there are differences in risk for species living in close proximity to humans or in areas affected by habitat loss, climate, and industry. Monitoring programs are essential to track the status of nesting pairs, offspring survival, longevity, and lifetime productivity. This is important for long-lived birds, such as vultures, that may be especially vulnerable to chronic exposure to chemicals as obligate scavengers. Furthermore, their position in the food web may increase risk due to biomagnification of chemicals. We review the primary chemical hazards to Old World vultures and the interacting stressors affecting these and other birds. Habitat is a major consideration for vultures, with tree-nesters and cliff-nesters potentially experiencing different risks of exposure to environmental chemicals. The present review provides information from long-term monitoring programs and discusses a range of these threats and their effects on vulture populations. Environ Toxicol Chem 2022;41:1586-1603. © 2022 SETAC.

Overview of Environmental and Health Effects Related to Glyphosate Usage

Since the introduction of glyphosate (N-(phosphomethyl) glycine) in 1974, it has been the most used nonselective and broad-spectrum herbicide around the world. The widespread use of glyphosate and glyphosate-based herbicides is due to their low-cost efficiency in killing weeds, their rapid absorption by plants, and the general mistaken perception of their low toxicity to the environment and living organisms. As a consequence of the intensive use and accumulation of glyphosate and its derivatives on environmental sources, major concerns about the harmful side effects of glyphosate and its metabolites on human, plant, and animal health, and for water and soil quality, are emerging. Glyphosate can reach water bodies by soil leaching, runoff, and sometimes by the direct application of some approved formulations. Moreover, glyphosate can reach nontarget plants by different mechanisms, such as spray application, release through the tissue of treated plants, and dead tissue from weeds. As a consequence of this nontarget exposure, glyphosate residues are being detected in the food chains of diverse products, such as bread, cereal products, wheat, vegetable oil, fruit juice, beer, wine, honey, eggs, and others. The World Health Organization reclassified glyphosate as probably carcinogenic to humans in 2015 by the IARC. Thus, many review articles concerning different glyphosate-related aspects have been published recently. The risks, disagreements, and concerns regarding glyphosate usage have led to a general controversy about whether glyphosate should be banned, restricted, or promoted. Thus, this review article makes an overview of the basis for scientists, regulatory agencies, and the public in general, with consideration to the facts on and recommendations for the future of glyphosate usage.

Peculiarities of herbicide use on oil flax in different soil and climatic conditions of the Western Ciscaucasia

The article presents the research results on the effect of pre-emergence and foliar herbicide treatments on the oil flax productivity in soil and climatic conditions of unstable and insufficient moistening zones of the Western Ciscaucasia. The pre-emergence application of herbicides Frontier Optima, EC (1.2 l/ha) or Dual Gold, EC (1.6 l/ha) on leached chernozem in the zone of unstable moistening led to an increase in the oil flax yield which exceeds the control with the manual weeding by 0.09 t/ha. The additional foliar treatment of sowings with Tifi, WDG (0.025 kg/ha) decreased the crop yield by 0.29 and 0.23 t/ha, respectively. The highest increase in yield (0.07 t/ha) on leached chernozem in the zone of insufficient moistening was achieved with the pre-emergence application of herbicide Dual Gold, EC (1.6 l/ha).

A Biological Trial on the Effect of Vitamin E and C Combination Therapy on Chronic Paraquat Toxicity

Paraquat (1,1-dimethyl-4-4-bipiridinium dichloride (PQ) is a non-selective contact herbicide that is a major source of free radicals and generates superoxide anion, and reactive oxygen species (ROS) which causes severe oxidative damage. Vitamin C is a water-soluble vitamin that plays a role using its biological characteristic as a suitable antioxidant in cells’ defense against oxygen deprivation and increasing tissue protection from oxidative stress. Vitamin E is a free-radical scavenger renowned for its anti-inflammatory and antioxidant properties. The purpose of the study was to determine the short-term therapeutic effect of a vitamin E and C combination treatment on paraquat-induced male albino rats. For the study, 200 male albino rats were used. The rats were divided into four major categories namely A, B, C, and D with 50 rats each. The "A" group received no paraquat, but the "B," "C," and "D" groups received 0.02g, 0.04g, and 0.06g of paraquat respectively every two weeks for three months. These groups were subsequently subgrouped into two with 25 rats per subgroup. The "A" group was divided into two "A0" and "AVE"; “B” was subgrouped into “B0” and BVEC”; “C” was subgrouped into “C0” and “CVEC” and “D” was subgrouped into “D0” and “DVEC”. A0, B0, C0 and D0 were subgroups without Vit E and C combined treatment while AVEC, BVEC, CVEC and DVEC were subgroups with combined treatment with 500mg of vitamin E and 2000mg/l of C medicated water every week for two months. Blood was drawn for the analysis of hematogical parameters (Hemoglobin concentration [Hb], Packed Cell volume [PCV], Total White blood cell count [T-WBC], Neutrophils and Lymphocytes). There was a significant variation in the hematological parameters among the "A0", "B0", "C0", and "D0" at p-value<0.05. There was also significant variation in the hematological parameters between the "AVEC", "BVEC", "CVEC", and "DVEC", p-value < 0.05. Consequently, it was also observed that there were significant variations in intra-group comparisons of Hb and PCV, p-value<0.05, whereas other markers were not statistically different. This study found that combining vitamin E and C has a therapeutic effect on ‘blood anemia indicators’ but not the immunity of male albino rats after one month of weekly treatment. As a result, a weekly treatment with Vit E and C combination therapy can alleviate PQ toxicity by ameliorating anemia but not affecting the immune system of male albino rats.

The effect of a novel herbicide adjuvant in treating Amur honeysuckle (Lonicera maackii)

AbstractInvasive woody perennials pose an immense threat to the diversity and function of many ecosystems, including forests in the eastern United States. While herbicide treatments have proven effective in controlling many plant invasions, there is considerable interest in the refinement of herbicide prescriptions to improve efficacy and prevent non-target damage. Adjuvants are widely utilized to improve herbicide efficacy, but research on novel adjuvants is often lacking. Furthermore, adjuvant research has generally focused on enhancement of foliar herbicide absorption, and few studies focus on adjuvant utility for other herbicide delivery techniques such as cut stump treatments. We evaluated 2XL—a cocktail of cellulase enzymes derived from fungi—as a potential herbicide adjuvant for use with glyphosate applied in a cut stump treatment due to its ability to degrade a key component of cell walls. We conducted a field experiment using the cut stump method of treatment (cut surface treated with herbicide) on a problematic invasive shrub, Amur honeysuckle [Lonicera maackii (Rupr.) Herder]. We tested combinations of three concentrations of 2XL with five concentrations of glyphosate and hypothesized that low concentrations of glyphosate combined with 2XL would be as effective in limiting the resprouting of L. maackii as higher concentrations of glyphosate without the enzymes. Our results indicated that 2XL did not improve glyphosate efficacy for reducing the number of resprouting stems or the length of the longest resprouting stem within the same or following year as treatment. Limited data indicated the combination of 2XL and glyphosate applied at 30 g L−1 slightly increased resprouting in the year following treatment. While 2XL did not improve glyphosate efficacy, our results showed effective control of L. maackii at the lowest concentration of glyphosate tested (30 g L−1), suggesting that concentrations lower than those typically applied may be effective in controlling L. maackii within parameters similar to those tested here.

Integrated Farming System: A Tool for Doubling Farmer’s Income

Integrated Farming System is a holistic approach in which different enterprises are utilized in a collaborative way, wherein the resources are managed efficiently so that waste output of one enterprise serves as the input for another. Due to an ever-increasing population, the arable land is becoming increasingly scarcer per person, leaving little room for horizontal agricultural expansion. There are 115 million working farms in India, with about 80% of them being small or marginal farmers. With Integrated Farming System, the living standards of these farmers can be enhanced by efficient utilization of different enterprises. The IFS is actually a mixed farming system wherein different enterprises like dairy, fish, poultry, and other beneficial enterprises give an enhanced returns with lower risks, which can intermediate the losses of crops in case of severe climatic conditions. Under IFS, various enterprises having lower dependency on severe weather circumstances, the farmer is comparatively on safer side as far as the adversities of crop losses are concerned There are many advantages to integrated farming systems (IFS), such as a more efficient use of farm resources and an eco-friendlier strategy to farming. As a system of crop and livestock farming, IFS consists of at least two distinct but logically interdependent parts. Water efficiency, weed and pest control, and soil health can all be improved with IFS. It also helps to maintain water quality. Chemical fertilisers, weed killers, and pesticides should be used sparingly in an integrated farming system in order to protect the environment from their harmful effects. Adopting an Integrated Farming System (IFS) ensures a stable and long-term source of farm income by integrating a number of businesses to make the most of the land's natural resources. IFS itself is important for sustainable development of farmer by improving yield, economic return, employment generation, nutritional security and livelihood.

Creation and identification of peanut germplasm tolerant to triazolopyrimidine herbicides

<p id="C3">At present, the germplasm resources of herbicide-tolerant peanut (<italic>Arachis hypogaea</italic>) are scarce, which restrict the diversification of peanut-based cropping system. To create peanut germplasm with tolerance to different herbicides, a mutant population consisting of more than 55,000 peanut lines were generated by ethylmethanesulfonate mutagenesis. We screened this population with a variety of different herbicides to obtain multiple mutants with tolerance to different herbicides. One of these lines displayed strong tolerance to florasulam and flumetsulam in the experiments with foliar herbicide spraying under field conditions as well as in various laboratory evaluation for the herbicide tolerance, while the herbicide-tolerant trait did not have adverse effects on peanut yield and quality. To determine whether this trait was associated with a target-site-based resistance to the herbicides, we compared gene sequences and relative expression levels of these two acetohydroxyacid synthases (AHASs) as the herbicide target enzymes between the mutant and wild type. Molecular cloning and sequence analysis revealed that peanut chromosome A10 and B10 each contained a gene, named as <italic>AhAHAS1a </italic>and <italic>AhAHAS1b</italic>, which were highly similar to <italic>Arabidopsis AHAS</italic>. Peanut chromosome A08 and B08 also each carried an <italic>AHAS</italic> gene, named as <italic>AhAHAS2a </italic>and <italic>AhAHAS2b</italic>, respectively. However, compared with the wild type, the genes in the mutants had no nucleotide substitutions that could alter the amino acid sequences. Furthermore, it was evident that there was no significant difference in the relative expression levels of <italic>AhAHAS</italic> genes between the mutant and wild type. In summary, these results indicate that the herbicide tolerance of the mutant might be caused by non-target-site-based resistance mechanism.

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Mechanistic Aspects and Effects of Selected Tank-Mix Partners on Herbicidal Activity of a Novel Fatty Acid Ester.

Only a limited number of contact herbicides exist in agricultural production. While systemic herbicides are more efficient also at suboptimum spray coverage with long-lasting weed control, contact herbicides provide several advantages. There is no translocation to fruits or roots of plantation and other crop, low risk for resistance development, and minor risk for spray-drift damage. Besides, synthetic products that often have toxicological or residues issues, natural fatty acids, particularly pelargonic acid (PA), have contact activity and are safer for home and garden use. We recently described a methyl capped polyethylene glycol ester of pelargonic acid (PA-MPEG) that acts independent of acid formation. Both, PA-MPEG and PA are applied at high rates per hectare to achieve excellent weed control. Here, we report about potential additives to increase PA-MPEG efficacy. The herbicidal active, 1-decanol, and the non-phytotoxic alkylated seed oil-based adjuvant, HastenTM, improved performance and outperformed a commercial PA herbicide. Both, PA-MPEG and PA appear to mainly act by the disintegration of bio-membranes besides having effects on transpiration. The main suggested effect is desiccation due to cutting the water continuum at the site of evaporation in the intercellular spaces. The synergistic action of the adjuvant HastenTM and its practical uses are also discussed.

Phytotoxic activity of Moldavian dragonhead (Dracocephalum moldavica L.) essential oil and its possible use as bio-herbicide

The incessant use of synthetic herbicides may cause several ecological problems including environmental contamination and developing herbicide-resistant species. These concerns led to exploring new eco-friendly weed control strategies. Present study is aimed to assess the phytotoxic activity of Moldavian dragonhead, Dracocephalum moldavica L., essential oil (EO) on Bromus tectorum L. All experiments were carried out as a completely randomized design with three replications. The EO of D. moldavica was analyzed using gas chromatography coupled with mass spectrometry (GC–MS). The outcomes of GC–MS showed that geranyl acetate (32.57 %), geranial (24.50 %), neral (22.65 %), and geraniol (8.78 %) are the major bioactive compounds of EO. As a result of treatment of B. tectorum with EO, seed germination and plantlet growth parameters were reduced in a concentration-dependent manner, and were completely suppressed with an essential oil concentration of 2 μL/mL. The content of pigments was also reduced in a dose-dependent manner. Although, antioxidant enzymes activities were enhanced in low concentrations of the EO, they were inhibited in high concentrations especially at 2 μL/mL. H2O2 and malondialdehyde content as well as electrolyte leakage were enhanced with the increasing concentration of EO. Overall, the outcomes of present study suggest that essential oil of D. moldavica can be used industrially to develop bio-herbicides owing to its noteworthy phytotoxic activity and weed killer potential.

How United States Agricultural Herbicides Became Military and Environmental Chemical Weapons: Historical and Residual Effects

Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later called this mechanism a plant’s hormone response system. Administrators and scientists, including Dr. Ezra J. Kraus, the Head of the Botany Department at the University of Chicago and a plant physiologist, suggested on the eve of WWII that weed killers had significant military value as chemical weapons. Dr. Kraus obtained access to a synthetic chemical, 2,4-D, and found that when the chemical was absorbed through the leaves of plants, it destroyed a plant’s hormones. After exposure, the plant experienced rapid and uncontrolled growth, and then the leaves shriveled, died and fell off. Dr. Kraus obtained funding for his Department of Botany research program from Department of Defense (DOD) during World War II (WWII). Camp Detrick (Biological Weapons Laboratory) scientists later obtained samples of newly created 2,4,5-T which contained unknown amounts of the by-product dioxin TCDD. In the 1950s and 1960s, Fort Detrick military scientists formulated the herbicide Agent Orange, which was a 50 - 50 mixture of 2,4-D and 2,4,5-T. These dual purpose herbicides were used by DOD and USDA. American and European farmers in the 1940s used 2,4-D and 2,4,5-T to eliminate weeds from pastureland and cropland. After WWII, synthetic herbicides (and pesticides) development continued in tandem with production of synthetic fertilizers and breeding of high-yield plant varieties. These new agricultural products were then shipped worldwide to increase crop yields, as part of the Green Revolution. This new system of agricultural technologies was intended to eliminate global starvation and increase food security by increasing field and farm crop yields. In contrast, the goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and wars. The primary objective of this research study is to describe how agricultural herbicides became tactical chemical weapons. A current assessment will address the environmental impacts of military and environmental chemical weapons on the United States and Vietnam ecosystems and need for additional dioxin TCDD hotspot clean-up efforts.

Flue‐cured tobacco response to sublethal rates of glufosinate

AbstractGlufosinate is a broad‐spectrum, contact herbicide that is currently applied to genetically engineered row crops that tolerate exposure to the compound. Flue‐cured tobacco (Nicotiana tabacum L.) is susceptible to glufosinate, yet it is commonly grown in close proximity to tolerant crops in North Carolina. The impact of glufosinate drift on flue‐cured tobacco is not known. Research was conducted in North Carolina to test the effects of sublethal rates of glufosinate (0.270, 0.135, 0.067, 0.034, 0.017 lb a.i. acre–1) on flue‐cured tobacco injury, yield, visual quality, financial value, and leaf chemistry. Simulated drift was imposed approximately 5 wk after transplanting. Visual injury increased with exposure rate and ranged from 15 to 83% and from 10 to 83% 1 and 2 wk after treatment, respectively. Cured leaf yield was reduced by 45% at the highest sublethal exposure rate and exhibited a linear decline of 47 lb acre–1 for every 0.01 lb glufosinate acre–1. Visual quality and per acre financial value were not affected by glufosinate, most likely due to the loss of necrotic tissue and late‐season plant growth compensation. Residues of glufosinate in green and cured leaves were likewise not detected. Producers and commercial applicators should exercise caution when applying glufosinate around flue‐cured tobacco because of the injury and yield loss that can result from physical spray drift, as well as the inability to sell tobacco that has been exposed to a pesticide that is not labeled for application.

Study of paraquat dichloride residue in oil palm

Paraquat dichloride is a non-selective contact herbicide commonly used in oil palm plantations. It causes the leaves to wilt quickly, dehydrate, and eventually die. The aim of this study was to evaluate the extent of paraquat residues in oil palm fruits. The study has conducted from November 2019 to February 2020. Fruit samples were collected from oil palm plantations in three provinces (North Sumatra, Jambi, and West Kalimantan). Paraquat is applied two times per year with a high volume spraying dose of one liter per hectare. The last application of paraquat dichloride was 30 days before harvest in North Sumatra and Jambi, and 14 days in West Kalimantan. The samples were taken randomly from five trees aged eight years (TM-8), then mixed for analysis. The result showed that paraquat residue content was undetected at the analytical detection limit of 0.0151 ppm. It means that the paraquat residue was below the detection level or that there was no residue in the oil palm fruits. As a result, the application of paraquat to control the weeds around the plantation leaves no residue in oil palm fruits.

Herbicide performance in the control of Conyza spp. where three plant heights

Intensive use of the herbicide glyphosate has led to herbicide resistant Conyza spp. populations. Thus, there is a need to indicate alternative herbicides and the appropriate developmental stage for controlling these populations. This study identifies alternatives for controlling glyphosate-resistant horseweed, with treatment applications at different plant heights. For this purpose, field experiments were conducted in the 2016/17 and 2017/18 crop years. The evaluated treatments were: glyphosate (540 g ae ha-1), glyphosate (1080 g ae ha-1), glyphosate (2160 g ae ha-1), glyphosate (3240 g ae ha-1), glyphosate + 2.4-D (1080 + 1005 g ae ha-1), glyphosate + saflufenacil (1080 + 49 g ae/ai ha-1), paraquat (400 g ai ha-1), diquat (400 g ai ha-1), ammonium glufosinate (600 g ai ha-1), and control (without application). These treatments were applied to plants with a maximum of 5 cm; plants between 6 and 15 cm; and plants between 16 and 25 cm. The results showed that glyphosate did not control weeds, regardless of rate. With the exception of 2,4-D, which needs complementation with sequential application of another contact herbicide, all alternatives were viable for the control of Conyza spp. plants with a maximum height of 5 cm.

A Review on Impact of Glyphosate on Development of Cancer

Pesticides are a vast mixture of compounds used to control pests like plants, moulds, and insects. In agriculture, non-agricultural vegetation management, and crop desiccant harvesting aid, chemicals from every major functional family of pesticides, such as insecticides, herbicides, fungicides, and fumigants, were frequently used. Herbicides are one of the most effective tools for farmers to obtain optimal crop yields when used correctly. Glyphosate (N-(phosphonomethyl) glycine) is a broad-spectrum weed killer that is used all over the world in agriculture and forestry. Glyphosate's herbicidal activity in plants is to disrupt the shikimic acid pathway's generation of branched-chain amino acids by preventing the binding of phosphoenolpyruvate (PEP) to the enzyme 5-enolpyruvylshikimate 3-phosphate synthase. This causes a deficiency in aromatic amino acid synthesis and, as a result, weeds mortality. Glyphosate exposure through food, drinking water, wind, water erosion, and other environmental pathways has been linked to human health issues as a carcinogen, mutagen, and reproductive toxicity. Glyphosate has a wide range of tumorigenic effects in biological systems, and epidemiological evidence suggests that glyphosate use on crops is linked to a wide range of cancers, including liver cancer, breast cancer, thyroid cancer, pancreatic cancer, kidney cancer, bladder cancer, and myeloid cancer. The shikimate pathway enzymes, intermediates, and derivative amino acids, which have been associated to genotoxicity and carcinogenicity, are thought to have a role in most cancer pathologies. This review summarises glyphosate's function in cancer pathology, including the ability of the glyphosate circuit to induce cancer and implications for future therapeutic methods.

Weed control in maize crops with various schemes of herbicide application

Goal. Carry out a comparative evaluation of the effectiveness of different schemes of application of modern herbicides in maize crops.&#x0D; Methods. Field, phenological, statistical. Conducted spraying of corn crops to seedlings (ВВСН 00) with herbicides Adengo 465 SC, hp (thiencarbazone-methyl, 90 g/l + isoxaflutol, 225 g/l + cyprosulfamide, 150 g/l), 0.5 l/ha, Primextra TZ Gold 500 SC, (S-metachlor. 312.5 g/l + terbuthylazine, 187.5 g/l), 4.5 l/ ha, Merlin Flex Duo 475 SC, (isoxaflutop, 50 g/l + cyprosulfamide, 50 g/l + terbuthylazine, 375 g/l, 2.0 l/ha. After germination in the phase of 4—5 leaves (ВВСН 14—15) applied insurance herbicides Milagro 040 SC, (nicosulfuron, 40 g/l), Basis 75 v.g. rimsulfuron, 500 g/kg + thifensulfuron-methyl, 250 g/l), MаisTer Power OD (foramsulfuron, 31.5 g/l + iodosulfuron-methyl sodium, 1.0 g/l + thiencarbazone-methyl, 10 g/l + cyprosulfamide, 15 g/l), Laudis 30 WG, VG (tembotrione, 200 g/kg + isoxadifen-ethyl, 100 g/kg) and Stellar, RK (topramezone, 50 g/l + dicamba, 160 g/k) in the recommended consumption rates. The experimental plots were 1000 m2 in the first experiment, the recurrence of 3-fold and 25 m2 in the second experiment, the recurrence of 4-fold. Observations were made for meteorological indicators. Statistical processing of the results was performed according to computer «Statgraphic plus» programs. &#x0D; Results. Mixed type of segetal vegetation prevailed in the experimental plots. Among the perennial weeds dominated by Sonchus arvensis L., Cirsium vulgare Savi Ten., Convolvulus arvensis L., among annuals — Setaria glauca L., Setaria viridis L., Echinochloa crus-galli L., Polygonum convolvulus L., Calinsoga parviflora L., Stellaria media (L.) Vill.), Chenopodium album L., Raphanus raphanistrum L., Thlaspi arvense L., Amaranthus retroflexus L. The application of pre-emergence herbicides effectively inhibited the growth and development of weeds. 60 days after application, the effectiveness of herbicides was 87—97% against cereals and 89—98% against dicotyledonous weeds, which did not require the application of insurance herbicides. During the critical periods of maize development, a sufficient level of soil moisture was recorded during the research years. After 60 days, the effectiveness of herbicides applied after crop germination was 65—95% against dicotyledonous and 65—92% against cereal weeds. The highest effect in killing weeds was provided by MaysTer Power, 1.5 l/ha, Laudis 30 WG, VG, 0.5 kg/ha + surfactant Mero, 2.0 l/ha and Stellar, RK, 1.25 l/ha + surfactant Metholate, 1.25 l/ha. The application of herbicides has significantly reduced the aboveground mass of weeds and increased crop yields. Maize grain yield from weed-protected areas was at the level of 8.0—9.7 t/ha against 4.1—4.9 t/ha in the control.&#x0D; Conclusions. Both herbicide application schemes under favorable weather conditions provide effective weed control of maize crops The efficiency of pre-emergence herbicides was at the level of 87—98%, post-emergence — 65—95%. At the same time, the reduction of aboveground mass of weeds was 75—95%, and crop yields increased by 1.6—2.2 times depending on the drug.

Stress and use of herbicides in field crops

When herbicides are combined under natural conditions or applied in stress conditions (drought, for instance), the efficiency of their action may decrease which results in considerable yield losses. The reason thereto is that another herbicide or stressor can trigger the adaptation mechanism in weed plants, and they survive, resulting in weed infestation. In particular, it applies to such herbicides as acetyl-CoA-carboxylase inhibitors or so- called graminicides, which are effective only for grass weeds control. The efficiency of this groups of herbi- cides is heavily dependent on the environment and often decreases when combined with herbicides, efficient against dicotyledon weeds. It turns out that this occurs due to the fact their final phytotoxicity is not determined at the level of the site of action (herbicide target) but depends on the stage of herbicide-induced pathogenesis – processes, occurring due to the interaction between the herbicide and its site of action. The stress response of the weeds may make its contribution into herbicide-induced pathogenesis. Plants are known to respond to the action of various abiotic stressors in the form of non-specific stress response and depending on the intensity and duration of the stressor’s action, a plant either adapts or dies. At present there are sufficient data, demonstrating that programmed cell death (PCD) is involved in the herbicide-induced pathogenesis. Reactive oxygen species (ROS) induce PCD in specific classes of herbicides. The participation of ROS and PCD in herbicide-induced pathogenesis allows for targeted effects on the phytotoxic action of herbicides, for instance, via combined application of herbicides with possible PCD inducers and prooxidants. The confirmation of the role of non- specific response in the development of phytotoxic action of herbicides is found in the phenomena of cross- adaptation (activation of antioxidant defense) and cross-synergism (activation of oxidative stress) under the application of herbicides. Based on our own research and literature data, the importance of cross-adaptation and cross-synergism in applying herbicides in drought conditions and to determine the nature of the interac- tion in herbicide complexes is discussed. In particular, the review discusses the reduction of phytotoxicity of the ACCase herbicides due to the phenomenon of cross-adaptation in drought conditions and in combination with herbicides, which are acetolactate synthase inhibitors. The results of investigations were presented about the reduction of antagonism in the mixtures of herbicides, which are ACCase and ALS inhibitors, because of the use of substances with prooxidant properties, as well as the inhibitor of the antioxidant enzyme superoxide dismutase. On the other hand, we analyzed the possibility of increasing the phytotoxic effect of herbicides, ACCase inhibitors, in combination with herbicides with prooxidant properties – inhibitors of electron transport in Photosystem 2 (FS 2) chloroplasts and protoporphyrinogen oxidase (PROTOX) inhibitors. It became the foundation for the elaboration of efficient herbicide compositions for wheat and onion fields. While combining herbicides, the issue of synergism is becoming relevant due to the problem of the spread of target-site resis- tance, since, to prevent this type of resistance, it is necessary to combine herbicides with different mechanisms of phytotoxicity. The presented data demonstrate that the increased activity of antioxidant defense systems, which is the result of a long process of evolutionary adaptation of weeds to the action of abiotic stressors, is an element of non-target-site-based resistance to herbicides. Possible ways to prevent the negative impact of non-specific stress response on the efficiency of herbicides, as well as the prospects of the chemical method of weeds control are discussed.