Benzoic Acid Herbicides Research Articles

Dicamba elevates concentrations of S-adenosyl methionine but does not induce oxidative stress or alter DNA methylation in rainbow trout (Oncorhynchus mykiss) hepatocytes

Dicamba is a benzoic acid herbicide used to target woody and broadleaf weeds in industrial, domestic, and municipal spheres. Because of its widespread use, dicamba is frequently detected in surface waters near sites of application. However, little is known regarding the effects of dicamba on freshwater fishes. In the present study, primary cultures of hepatocytes from rainbow trout (Oncorhynchus mykiss) were exposed to either an environmentally relevant (0.22 or 2.2 μg L−1) or supra-environmental (22 μg L−1) concentration of dicamba for 48 h to investigate if oxidative stress is a mechanism of toxicity. mRNA abundances of genes involved in the response to oxidative stress, levels of lipid peroxidation, and concentrations of glutathione and s-adenosyl methionine (SAM) were quantified. Results indicate that dicamba does not induce oxidative stress. However, exposure to 2.2 μg L−1 of dicamba did cause a 5.24-fold increase in concentrations of SAM. To investigate the mechanisms of increased SAM, effects of dicamba on global and genome-wide DNA methylation were quantified. Dicamba did not cause changes to DNA methylation. Overall, dicamba was not acutely toxic to hepatocytes and did not cause oxidative stress or changes in DNA methylation at environmentally relevant concentrations.

Development and validation of thin layer chromatography method for simultaneous determination of seven chlorophenoxy and benzoic acid herbicides in water

Thin layer chromatography (TLC) densitometric method for simultaneous determination of seven chlorophenoxy and benzoic acid herbicides (2,4-D; 2,4,5-T; MCPA; 2,4-DP; MCPP; Dicamba and MCPB) in water samples was developed and validated. A mobile phase consisted of benzene−dioxane−glacial acetic acid in ratio of 45: 10: 2 and TLC silica gel 60 F254 aluminium plate were used. Detection was carried out densitometrically at 280 nm. The linearity was obtained in the range 20–200 ng per band with the correlation coefficient between the peak area and concentration for each analyte higher than 0.9976. The limits of detection and quantification were 18 and 60 ng per band, respectively. The recoveries of analyzed herbicides varied from 84.5 to 92.7%. The method can be used for routine quality analysis of chlorophenoxy and benzoic acid herbicides in natural surface and ground water samples.

Degradation of the herbicide dicamba by two sphingomonads via different O-demethylation mechanisms

Dicamba, a chlorinated benzoic acid herbicide, is widely used to control broadleaf weeds. In this study, two dicamba-degrading sphingomonads Sphingobium sp. Ndbn-10 and Sphingomonas sp. Ndbn-20 were isolated from activated sludge and compost samples, respectively. Both isolates could completely degrade and utilize dicamba, but strain Ndbn-10 possessed relatively higher dicamba degradation efficiency than strain Ndbn-20. The degradation of dicamba in both isolates was initiated by O-demethylation to generate 3,6-dichlorosalicylic acid (DCSA) but through different mechanisms. For Sphingobium sp. Ndbn-10, O-demethylation is catalyzed by a NADH-dependent dicamba monooxygenase (DMO), whereas in Sphingomonas sp. Ndbn-20, a tetrahydrofolic acid (THF)-dependent O-demethylase is responsible for the O-demethylation. Our results suggest that sphingomonads can rapidly and efficiently adapt to degrading dicamba through the evolution of different metabolic pathway mechanisms and highlight a novel THF-dependent dicamba O-demethylation mechanism in bacteria.

Development and Validation of Thin Layer Chromatography Method for Simultaneous Determination of Seven Chlorophenoxy and Benzoic Acid Herbicides in Water

Development and Validation of Thin Layer Chromatography Method for Simultaneous Determination of Seven Chlorophenoxy and Benzoic Acid Herbicides in Water

Dicamba affects sex steroid hormone level and mRNA expression of related genes in adult rare minnow (Gobiocypris rarus) at environmentally relevant concentrations

Dicamba is a benzoic acid herbicide that has been detected in surface and ground water. The herbicide has been shown to have cytogeneic and DNA damaging effects and to cause organ damage in mammals; however, little is known about the endocrine disrupting effects of dicamba in fish. In this study, histological changes, plasma vitellogenin (VTG) and sex hormone levels, and mRNA expression of sex steroid hormone-related genes were determined in adult rare minnow exposed to environmentally relevant concentrations of dicamba (0, 0.05, 0.5, 5, and 50 μg/L) for 40 days. The results showed inhibition of spermatogenesis in male testes and ovarian degeneration in females. Plasma 17β-estradiol (E2) levels were significantly increased in both genders, and plasma VTG levels were significantly increased in males (p<0.05). These results indicate that sex hormone homeostasis and normal reproduction of fish could be affected by dicamba. Moreover, the mRNA levels of vtg were significantly upregulated in the livers and gonads of both male and female rare minnows (p < 0.05). The downregulation of cytochrome P450c19a (cyp19a) and steroidogenic acute regulatory protein (star) mRNA levels, and the upregulation of cytochrome P450c17 (cyp17) mRNA levels were observed in the livers and ovaries (p<0.05). The results of the mRNA analysis suggest that changes in steroid hormone-related gene expression could serve as a regulatory mechanism to maintain sex hormone homeostasis. Overall, dicamba exposure could result in histological lesions, plasma VTG increases, changes in sex hormone levels, and alterations of hormone-related gene expression. Therefore, dicamba should be considered to be a potential endocrine disruptor.

Treatment of 2,4-D, mecoprop, and dicamba using membrane bioreactor technology

Phenoxyacetic and benzoic acid herbicides are widely used agricultural, commercial, and domestic pesticides. As a result of high water solubility, mobility, and persistence, 2,4-dichlorophenoxyacetic acid (2,4-D), methylchlorophenoxypropionic acid (mecoprop), and 3,6-dichloro-2-methoxybenzoic acid (dicamba) have been detected in surface and waste waters across Canada. As current municipal wastewater treatment plants do not specifically address chronic, trace levels of contaminants like pesticides, an urgent need exists for an efficient, environmentally friendly means of breaking down these toxic herbicides. A commercially available herbicide mix, WeedEx, containing 2,4-D, mecoprop, and dicamba, was subjected to treatment using membrane bioreactor (MBR) technology. The three herbicides, in simulated wastewater with a chemical oxygen demand of 745 mg/L, were introduced to the MBR at concentrations ranging from 300 μg/L to 3.5 mg/L. Herbicides and biodegradation products were extracted from MBR effluent using solid-phase extraction followed by detection using high-performance liquid chromatography coupled with mass spectrometry. 2,4-D was reduced by more than 99.0 % within 12 days. Mecoprop and dicamba were more persistent and reduced by 69.0 and 75.4 %, respectively, after 112 days of treatment. Half-lives of 2,4-D, mecoprop and dicamba during the treatment were determined to be 1.9, 10.5, and 28.3 days, respectively. Important water quality parameters of the effluent such as dissolved oxygen, pH, ammonia, chemical oxygen demand, etc. were measured daily. MBR was demonstrated to be an environmentally friendly, compact, and efficient method for the treatment of toxic phenoxyacetic and benzoic acid herbicides.

Weed Management in Pastures and Rangeland - 2009

Revised! SS-AGR-08, a 13-page fact sheet by B.A. Sellers and J.A. Ferrell, describes mechanical control, sanitation, chemical control, postemergence applications, and precautions to take when using phenoxy or benzoic acid herbicides. Published by the UF Department of Agronomy, January 2009. SS-AGR-08/WG006: Weed Management in Pastures and Rangeland—2020 (ufl.edu)

A single polymerase chain reaction‐based assay for simultaneous detection of two mutations conferring resistance to tubulin‐binding herbicides in Setaria viridis

SummaryA simple method based upon polymerase chain reaction (PCR) was developed to detect mutant alleles of the gene encoding α2‐tubulin, which confers recessive resistance to tubulin‐binding herbicides in Setaria viridis. Multiplex, bidirectional allele‐specific PCR (Mbi‐PASA) was shown to specifically and reliably detect the presence of all sensitive (Leu136, Thr239) and resistant (Phe136, Ile239) α2‐tubulin alleles in a single reaction. Double‐blind analysis of 2000 S. viridis seedlings using seed bioassay and Mbi‐PASA confirmed that the presence of two mutant α2‐tubulin alleles in a seedling was always associated with cross‐resistance to dinitroaniline and benzoic acid herbicides, sensitivity to a benzamide herbicide, and hypersensitivity to carbamate herbicides. No other resistance mechanism was detected in the S. viridis populations screened. Successful Mbi‐PASA genotyping was achieved with fresh and dried plant fragments from the field. Compared with bioassays, Mbi‐PASA is faster and more robust, removing the need for live plant material. It is the only way of detecting recessive resistance before resistant plants occur in a field. Mbi‐PASA can be performed with basic molecular biology laboratory equipment, and is suitable for high‐throughput genotyping adaptation. It is the tool of choice for resistance diagnosis in such cases where only a few recessive, target‐derived, genes control resistance to herbicides.

PRECONCENTRATION OF PHENOXY ACID HERBICIDE RESIDUES BY USING AN ION EXCHANGER BASED ON MFE-POLYMER

An anion exchanger based on MFE-Polymer (hydroxy-ethylmethacrylate, HEMA) containing quaternary ammonium functional groups has been used to pack a 150 × 4.6 mm id steel column, and the efficiency of this ion exchanger to preconcentrate phenoxy acid herbicides residues has been studied. The phenoxy acid herbicides studied were 2,4-dichlorophenoxy acetic acid (2,4-D), 4-(2,4-dichlorophenoxy)-butanoic acid (2,4-DB), 2,4,5-trichlorophenoxy acetic acid (2,4,5-T), 2-(2,4,5-trichlorophenoxy)-propanoic acid (2,4,5-TP), and 4-chloro-2-methylphenoxy acetic acid (MCPA). Dicamba (3,6-dichloro-2-methoxybenzoic acid), a benzoic acid herbicide usually used in technical products in mixtures with some of the related phenoxy acids, has also been included in the study. Retention of these herbicides on the referred ion exchanger is possible in aqueous acidic medium, probably because of the high polarizing power of the quaternary ammonium groups over the studied herbicides. Subsequent elution from the column was made with methanol containing nitric acid 60 mM and not more than 10 mL are required. The influence of the flow rate in the retention of the herbicides was evaluated in the 1.0 – 9.0 mL/min range, achieving recoveries around 100% for all of the herbicides studied. Regarding the capacity of the anion exchanger, the column prepared can retain up to 1000 μg of each herbicide. The good ability for retention and elution allows the LC determination of these herbicides in tomato samples at levels of 0.05 mg/kg with a minimum clean-up.

Effect of phenoxy and benzoic acid herbicides on nitrogenase activity and growth of Azospirillum brasilense

Signalement de l'effet inhibiteur du 2,4-D, du MCPA, du 2,3,6-TBA, du dicamba sur la fixation d'azote et sur la croissance de cultures pures en milieu malate

The Metabolism of Atrazine, Chloramben, and Dicamba in Earthworms (Lumbricus terrestris) from Treated and Untreated Plots

The metabolism of three 14C-ring-labeled herbicides, atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], chloramben (3-amino-2,5-dichlorobenzoic acid), and dicamba (3,6-dichloro-o-anisic acid) was studied in the earthworm, Lumbricus terrestris L., taken from plots treated with these herbicides for the past 10 yr and from control plots treated with no herbicides. For the two benzoic acid herbicides, acetone extracts of sand and earthworms from untreated plots contained more unmetabolized herbicide than similar extracts of sand and earthworms from treated plots, indicating a net enhancement of metabolism in worms from treated plots. For atrazine, the amount of unchanged herbicide in the acetone extracts of earthworm and sand were nearly equivalent. Finally, the relative metabolic stability of the three herbicides in decreasing order in earthworms from both control and untreated plots was chloramben&gt;atrazine&gt;dicamba.

Regulation of Lipid Synthesis in Soybeans by Two Benzoic Acid Herbicides

The effects of 3-nitro-2,5-dichlorobenzoic acid (dinoben) and 3-amino-2,4-dichlorobenzoic acid (chloramben) on lipid formation and on the incorporation of various substrates into lipids by intact seeds and subcellular fractions of germinating soybean (Glycine max [L.] Merr. ;Amsoy') were studied. Dinoben (20 mug/ml) inhibited synthesis of total lipids 67%, neutral lipids 73%, glycolipids 51%, and phospholipids 39% in germinating seeds. When polar lipids were analyzed further, inhibition of individual lipid classes was also observed. Chloramben (20 mug/ml) stimulated total lipid synthesis 25%. With the exception of the mitochondrial fraction where malonate thiokinase was absent, dinoben inhibited up to 99% the incorporation of acetate and malonate into lipids, but did not inhibit acetyl-CoA and malonyl-CoA incorporation. Chloramben stimulated the incorporation of all substrates tested into lipids by all fractions except the mitochondrial fraction when malonate was the substrate. When dinoben and chloramben were used in combinations, chloramben did not reverse the inhibitory effect of dinoben.It is concluded that the dinoben inhibitory effect is specific and is associated with the acetate and malonate thiokinase systems. The chloramben effect is stimulatory to either acetyl-CoA carboxylase or fatty acid synthetase or both.

Herbicide Influence on Arrowleaf Clover Seedling Establishment1

The chlorophenoxy and benzoic acid herbicides are used extensively for the control of pasture weeds. The increasing importance of legumes to the pasture ecosystem has made it necessary to determine the influence of these herbicides on certain forage species. The purpose of this study was to determine the influence of chlorophenoxy and benzoic acid herbicides on ‘Amclo,’ ‘Yuchi,’ and ‘Meechi’ arrowleaf clover (Trifolium vesiculosum Savi.) germination and seedling development. The experiments were conducted in a programmed germinator and the greenhouse.Increasing 2,4‐D [(2,4‐dichlorophenoxy)acetic acid] concentration decreased the percent germination of Yuchi. Whereas, 750 ppb 2,4,5‐T [(2,4,5‐trichlorophenoxy)acetic acid] and MCPA ([(4‐chloro‐v.tolyl)oxy]acetic acid) 500 ppb 2,4‐DB[4.(2,4‐dichlorophenoxy)butyric acid] adversely influenced the seed germination of Yuchi, Amclo, and Meechi, respectively.The lowest concentration (63 ppb) of all herbicides except 2,4,5‐T reduced radicle development on all three cultivars. The 63 ppb treatment of 2,4,5‐T stimulated radicle development on Meechi and Yuchi. The order of increasing influence of these herbicides on seedling establishment was 2,4‐DB &lt; 2,4,5‐T = 2,4‐D &lt; MCPA = dicamba [3,6‐dichloro‐o‐anisic acid].

Effects of Soil pH and Moisture on the Direct Radioassay of Herbicides in Soil

The addition of 1.5 ml water or 1.5 ml 0.1 N oxalic acid solution to 2 g soil samples containing 14C-labeled herbicides increased the 14C extraction efficiencies. The employment of a modified dioxane extracting-counting solution allowed the addition of 2 ml water without causing a liquid phase separation. Extraction of benzoic acid herbicides from soil was enhanced when 5 mg oxalic acid was added to 2 g soil or when soil was acidified to pH 4.1.

The Phytotoxicity and Persistence in Soils of Benzoic Acid Herbicides

The Phytotoxicity and Persistence in Soils of Benzoic Acid Herbicides

Toxicity of Benzoic Acid Herbicides to Cotton and Soybeans

Toxicity of Benzoic Acid Herbicides to Cotton and Soybeans