Metabolic Resistance to Protoporphyrinogen Oxidase-Inhibitor Herbicides in a Palmer amaranth Population from Kansas.

Palmer amaranth has evolved target and nontarget site resistance to protoporphyrinogen oxidase-inhibitor herbicides in the United States. Recently, a population (KCTR) from a long-term conservation tillage study in Kansas was found to be resistant to herbicides from six sites of action, including to PPO-inhibitors, even with this herbicide group being minimally used in this field. This research investigated the level of resistance to postemergence PPO-inhibitors, target- and nontarget-site resistance mechanism(s), and efficacy of pre-emergence chemistries. The greenhouse experiments confirmed 6.1- to 78.9-fold resistance to lactofen in KCTR, with the level of resistance increasing when KCTR was purified for the resistance trait. PPO2 sequences alignment revealed the absence of known mutations conferring resistance to PPO-inhibitors in KCTR Palmer amaranth, and differential expression of the PPO2 gene did not occur. KCTR metabolized fomesafen faster than the susceptible population, indicating that herbicide detoxification is the mechanism conferring resistance in this population. Further, treatment with the cytochrome P450-inhibitor malathion followed by lactofen restored the sensitivity of KCTR to this herbicide. Despite being resistant to POST applied PPO-inhibitors, KCTR Palmer amaranth was completely controlled by the labeled rate of the PRE applied PPO-inhibitors fomesafen, flumioxazin, saflufenacil, sulfentrazone, and oxadiazon. The overall results suggest that P450-mediated metabolism confers resistance to PPO-inhibitors in KCTR, rather than alterations in the PPO2, which were more commonly found in other Palmer amaranth populations. Future work will focus on identifying the fomesafen metabolites and on unravelling the genetic basis of metabolic resistance to PPO-inhibitor herbicides in KCTR Palmer amaranth.

Development of an immunoassay based on a specific antibody for the detection of diphenyl ether herbicide fomesafen.

Fomesafen belongs to the diphenyl ether herbicide, and is widely used in the control of broadleaf weeds in crop fields due to its high efficiency and good selectivity. The residual of fomesafen in soil has a toxic effect on subsequent sensitive crops and the microbial community structure because of its long residual period. Therefore, an efficient method for detecting fomesafen is critical to guide the correct and reasonable use of this herbicide. Rapid and sensitive immunoassay methods for fomesafen is unavailable due to the lack of specific antibody. In this study, a specific antibody for fomesafen was generated based on rational design of haptens and a sensitive immunoassay method was established. The half maximal inhibitory concentration (IC50) of the immunoassay was 39 ng/mL with a linear range (IC10-90) of 1.92-779.8 ng/mL. In addition, the developed assay had a good correlation with the standard UPLC-MS/MS both in the spike-recovery studies and in the detection of real soil samples. Overall, the developed indirect competitive enzyme immunoassay reported here is important for detecting and quantifying fomesafen contamination in soil and other environmental samples with good sensitivity and high reproducibility.

A solar evaporator fabricated from corncob waste for the desalination of seawater and removal of oil/herbicides from contaminated water.

Corncob (CC) based solar evaporators were employed to desalinize seawater brought from the Vallarta coast in Mexico. The pure CC produced an evaporation-rate and evaporation-efficiency of 0.63 kg m-2 h-1 and 38.4%, respectively, under natural solar light. Later, the CC was coated with carbonized CC (CCCE evaporator) or was coated with graphene (CCGE evaporator). Those evaporators were used for the desalination of seawater and obtained higher evaporation rates of 1.59-1.67 kg m-2 h-1, and higher evaporation efficiencies of 92-94% (under natural solar light). The desalination experiments were repeated under artificial solar light and the evaporation-rates/evaporation-efficiencies slightly decreased to 1.43-1.52 kg m-2 h-1/88-92%. The surface analysis of the evaporators by FTIR, XPS and Raman revealed that the CCGE evaporator had on its surface a lower content of defects and a higher amount of OH groups than the CCCE evaporator. Therefore, the CCGE evaporator had higher evaporation-rates/evaporation-efficiencies in comparison with the CCCE evaporator. Furthermore, we purified water contaminated with three different herbicides (fomesafen, 2-6 dichlorobenzamide and 4-chlorophenol at 30 ppm) by evaporation and using natural solar light. Interestingly, the CCCE and CCGE evaporators also removed the herbicides by physical adsorption with efficiencies of 12-22.5%. Moreover, the CCGE evaporator removed vegetable oil from contaminated water by adsorption and its maximum adsorption capacity was 1.72 g/g. Overall, our results demonstrated that the corncob-based evaporators studied here are a low-cost alternative to obtain clean water under natural solar light and this one was more effective for the desalination of seawater than the artificial sunlight (Xe lamp).

Remediation of fomesafen contaminated soil by Bacillus sp. Za: Degradation pathway, community structure and bioenhanced remediation.

Fomesafen is a diphenyl ether herbicide used to control the growth of broadleaf weeds in bean fields. The persistence, phytotoxicity, and negative impact on crop rotation associated with this herbicide have led to an increasing concern about the buildup of fomesafen residues in agricultural soils. The exigent matter of treatment and remediation of soils contaminated with fomesafen has surfaced. Nevertheless, the degradation pathway of fomesafen in soil remains nebulous. In this study, Bacillus sp. Za was utilized to degrade fomesafen residues in black and yellow brown soils. Fomesafen's degradation rate by strain Za in black soil reached 74.4%, and in yellow brown soil was 69.2% within 30 days. Twelve intermediate metabolites of fomesafen were identified in different soils, with nine metabolites present in black soil and eight found in yellow brown soil. Subsequently, the degradation pathway of fomesafen within these two soils was inferred. The dynamic change process of soil bacterial community structure in the degradation of fomesafen by strain Za was analyzed. The results showed that strain Za potentially facilitate the restoration of bacterial community diversity and richness in soil samples treated with fomesafen, and there were significant differences in species composition at phylum and genus levels between these two soils. However, both soils shared a dominant phylum and genus, Actinobacteriota, Proteoobacteria, Firmicutes and Chloroflexi dominated in two soils, with a high relative abundance of Sphingomonas and Bacillus. Moreover, an intermediate metabolite acetaminophen degrading bacterium, designated as Pseudomonas sp. YXA-1, was isolated from yellow brown soil. When strain YXA-1 was employed in tandem with strain Za to remediate fomesafen contaminated soil, the degradation rate of fomesafen markedly increased. Overall, this study furnishes crucial insights into the degradation pathway of fomesafen in soil, and presents bacterial strain resources potentially beneficial for soil remediation in circumstances of fomesafen contamination.

Investigation of resistance mechanisms to fomesafen in Ipomoea nil from China.

Recently, the herbicide fomesafen has frequently failed to control the troublesome weed Ipomoea nil in soybean fields in Liaoning Province, China. Hence, we collected 10 suspected resistant populations and evaluated their sensitivity to fomesafen. The results revealed various degrees of Ipomoea nil resistance to fomesafen, with a resistance index of 2.88 to 22.43; the highest value occurred in the LN3 population. Therefore, the mechanisms of the resistance in LN3 to fomesafen were explored. After fomesafen treatment, the expression levels of InPPX1 and InPPX2 genes were 4.19- and 9.29-fold higher, respectively, in LN3 than those in the susceptible (LN1) population. However, mutations and copy number variations were not detected between the two populations. Additionally, malathion pretreatment reduced the dose necessary to halve the growth rate of LN3 by 58%. Liquid chromatography with tandem mass spectrometry demonstrated that metabolism of fomesafen was significantly suppressed by malathion. Moreover, LN3 displayed increased reactive oxygen species scavenging capacity, which was represented by higher superoxide dismutase and peroxidase activities after fomesafen application than those in LN1. An orthogonal partial least squares-discriminant analysis revealed that the high resistance in LN3 could be attributed mainly to enhanced metabolism. Fortunately, the fomesafen-resistant I. nil remained sensitive to 2,4-D-ethylhexylester and bentazon, providing methods for its control.

Research progress on residual characteristics, ecological risk, and abatement of fomesafen in farmland soil.

Fomesafen, a long residual diphenyl ether herbicide, is widely used for control of annual and perennial broadleaf weeds in peanut and soybean fields. With the development of agricultural production mechanization in China, the application of fomesafen has been rising. Long-term and large-scale application leads to obvious residues in the soil. As a consequence, the resulting ecological and environmental problems need urgent attention from the agricultural and environmental protection departments. We systematically reviewed the research progress about the residual characteristics, ecotoxicological effects and abatement process of fomesafen in farmland soil, and proposed some prospects from the residual formation mechanisms, safe application limit standard, abatement mechanism and technology, aiming to provide some new insights and ideas for solving the problem of residual injury of fomesafen.

Detoxification and catabolism of mesotrione and fomesafen facilitated by a Phase II reaction acetyltransferase in rice.

INTRODUCTION: The excessive dosage of pesticides required for agronomic reality results in growing contamination of pesticide residues in environment, thus bringing high risks to crop production and human health. OBJECTIVES: This study aims to unveil a novel mechanism for catabolism of two pesticides MTR and FSA facilitated by an uncharacterized Phase II reaction enzyme termed acetyltransferase-1 (ACE1) in rice and to make assessment of its potential for bioremediation to minimize the risks to crop production and food safety. METHODS: We developed genetically improved cultivars overexpressing OsACE1 (OE) and knockout mutant lines by CRISPR-Cas9 technology to identify the MTR and FSA detoxic and metabolic functions and characterized their metabolites and conjugates by HPLC-LTQ-MS/MS. RESULTS: OsACE1 overexpression conferred rice resistance to toxicity of MTR/FSA compared to wild-type, manifested by improved plant elongation and biomass, attenuated cellular injury, and increased chlorophyll accumulation. The OE plants accumulated significantly less parent MTR/FSA and more degradative metabolites, and removed MTR/FSA from their growth medium by 1.38 and 1.61 folds over the wild-type. In contrast, knocking out OsACE1 led to compromised growth fitness and intensified toxic symptoms under MTR/FSA stress and accumulation of more toxic MTR and FSA in rice. The reduced metabolites of MTR and FSA detected in the Cas9 plants suggest the impaired capability of OsACE1 function. CONCLUSIONS: These results signified that OsACE1 expression is required for detoxifying the two poisoning chemicals in rice and plays a critical role in accelerating breakdown of the pesticides mainly through Phase II reaction mechanism pathways.

Target gene mutation and enhanced metabolism confer fomesafen resistance in an Amaranthus retroflexus L. population from China.

Amaranthus retroflexus L., a troublesome annual dicotyledonous weed species, is highly competitive with soybean (Glycine max L.). A single-dose herbicide-resistance screening assay identified an A. retroflexus population with suspected resistance to fomesafen. Whole-plant dose-response assays demonstrated that the resistant population (2492) was resistant to protoporphyrinogen oxidase (PPO)-inhibiting herbicides (50.6-fold fomesafen resistance and > 8.1-fold lactofen resistance) compared to a susceptible (S) population. PPX2 gene sequence analysis showed an Arg128Gly amino acid substitution in the 2492 population. Moreover, pretreatment of malathion and the fomesafen metabolic assays through HPLC-MS demonstrated enhanced fomesafen metabolism in the 2492 population. Additionally, the 2492 population was 10.4-fold more resistant to the ALS-inhibiting herbicide imazethapyr and 16.8-fold more resistant to thifensulfuron-methyl than the S population. ALS gene sequence analysis showed an Ala205Val amino acid substitution in the 2492 population. This population of A. retroflexus has coexisting target-site resistance and non-target-site mechanisms for resistance to fomesafen. Multiple herbicide resistance may mean it is necessary to adjust weed management strategies to better control the resistant population.

Multiple resistance to ALS-inhibiting and PPO-inhibiting herbicides in Chenopodium album L. from China.

Common lambsquarters (Chenopodium album L.) is a broadleaf weed that can severely damage soybean fields. Two C. album populations (1744 and 1731) suspected resistant to imazethapyr were investigated for resistance levels to imazethapyr, thifensulfuron-methyl, and fomesafen and their resistance mechanisms were investigated. Whole-plant dose-response assays revealed that, compared to the susceptible (S) population, the 1744 population was 16.5-fold resistant to imazethapyr, slightly resistant to thifensulfuron-methyl (resistance index [R/S], <3). The 1731 population was 18.8-fold resistant to imazethapyr, 2.9-fold resistant to thifensulfuron-methyl, and 5.1-fold resistant to fomesafen. In vitro acetolactate synthase (ALS) assays showed 17.1-fold and 19.3-fold resistance levels of 1744 and 1731 populations to imazethapyr respectively. ALS gene sequence analysis identified Ala122Thr amino acid substitution in the 1744 population and Ser653Thr amino acid substitution in the 1731 population. No mutations of the protoporphyrinogen oxidase (PPO) gene were detected. However, pre-treatment with malathion reversed fomesafen resistance, suggesting nontarget-site resistance mechanisms likely play a role in the 1731 population.

Field-Evolved ΔG210-ppo2 from Palmer Amaranth Confers Pre-emergence Tolerance to PPO-Inhibitors in Rice and Arabidopsis.

Resistance to protoporphyrinogen IX oxidase (PPO)-inhibitors in Amaranthus palmeri and Amaranthus tuberculatus is mainly contributed by mutations in the PPO enzyme, which renders herbicide molecules ineffective. The deletion of glycine210 (ΔG210) is the most predominant PPO mutation. ΔG210-ppo2 is overexpressed in rice (Oryza sativa c. 'Nipponbare') and Arabidopsis thaliana (Col-0). A foliar assay was conducted on transgenic T1 rice plants with 2× dose of fomesafen (780 g ha−1), showing less injury than the non-transgenic (WT) plants. A soil-based assay conducted with T2 rice seeds confirmed tolerance to fomesafen applied pre-emergence. In agar medium, root growth of WT rice seedlings was inhibited >90% at 5 µM fomesafen, while root growth of T2 seedlings was inhibited by 50% at 45 µM fomesafen. The presence and expression of the transgene were confirmed in the T2 rice survivors of soil-applied fomesafen. A soil-based assay was also conducted with transgenic A. thaliana expressing ΔG210-ppo2 which confirmed tolerance to the pre-emergence application of fomesafen and saflufenacil. The expression of A. palmeri ΔG210-ppo2 successfully conferred tolerance to soil-applied fomesafen in rice and Arabidopsis. This mutant also confers cross-tolerance to saflufenacil in Arabidopsis. This trait could be introduced into high-value crops that lack chemical options for weed management.

Identification, characterization and expression of rice (Oryza sativa) acetyltransferase genes exposed to realistic environmental contamination of mesotrione and fomesafen.

The plant acetyltransferases (ACEs) belong to a super family of proteins that contribute to secondary metabolisms and involve various abiotic and biotic stress responses. However, how rice ACEs respond to toxic agrochemicals is largely unknown. This study demonstrates that 86 and 83 genes coding ACEs in the transcriptome profiling were expressed under mesotrione (MTR) and fomesafen (FSA) exposure, respectively. Of these, 18 and 8 ACE differentially expressed genes (DEGs) were identified in MTR- and FSA-exposed rice transcriptome datasets. Some of the ACE genes were validated by quantitative RT-PCR analysis. Analysis of biochemical properties of ACEs revealed that many genes have various cis-elements and structural domain which may cope with a variety of biotic and abiotic stress responses and detoxification of xenobiotics. Moreover, the ACE activities in rice were induced under MTR and FSA exposure and reached out to the highest value at the 0.1 mg L-1. The ACE activities in the MTR and FSA treated roots were 2.6 and 3.5 fold over the control and those in shoots with MTR and FSA were 4.0 and 26.1 fold over the control, respectively. These results indicate that the ACE-coding genes can respond to the MTR and FSA stress by increasing their transcriptional level, along with the enhanced specific ACE protein activities in rice tissues.

Effect of Soil Type and Temperature on Persistence and Dissipation Kinetics of a New Readymix Formulation of Fomesafen + Quizalofop-ethyl.

The research portrays the fate of a new herbicide mixture of fomesafen and quizalofop-ethyl. The soil samples viz. red lateritic soil (A), coastal saline soil (B) and black soil (C) were fortified separately for fomesafen and quizalofop-ethyl at 0.5 (T1) and 1.0 mg kg-1 (T2) doses and incubated at 20, 30 and 40°C. A satisfactory mean recovery, precision and linearity proved that the methods were accurate. Both the herbicides followed first + first order kinetics. Higher persistence of fomesafen was observed in Soil C than Soil B and Soil A with 22.38-53.75 days half-life, whereas quizalofop-ethyl showed higher stability in Soil A than Soils B and C with half-life of 0.93-12.07 days. Both compounds showed faster rates of dissipation at increased temperature, irrespective of soil type. The current study will help to predict the effect of temperature on the dissipation of herbicides in different soil under real field scenario.

Exposure to fomesafen alters the gut microbiota and the physiology of the earthworm Pheretima guillelmi.

The application of herbicide fomesafen plays a crucial role in ensuring global soybean productivity in modern agriculture, but it results in both adverse effects on soil ecosystems and phytotoxicity to succeeding crops. Soil pollution due to herbicides has raised much concern worldwide. However, there has been little investigations concerning their effects on soil fauna, especially on the gut microbial communities of earthworms. In this study, the soil endogeic earthworm Pheretima guillelmi was incubated for 20 days in natural and fomesafen-polluted soils to investigate the effects of the herbicide on gut bacterial microbiota and the earthworm's physiological indices, including energy resource (protein) and antioxidant enzyme (superoxide dismutase, SOD) of earthworms in the soil ecosystem. A significantly different and smaller microbial community was presented in the earthworm's gut compared with the cast and the surrounding soil, with exposure to fomesafen further reducing the bacterial diversity and altering the gut community composition. This was observed as significant changes in the relative abundance of the phyla Actinobacteria, Firmicutes, and Proteobacteria as well as the genera Bacillus, Microvirga, Blastococcus, Nocardioides, and Gaiella. Moreover, exposure to fomesafen reduced earthworms' energy resources and activated the antioxidant system, with both effects being significantly correlated with the gut microbial diversity. These findings unravel the fact that exposure to the herbicide fomesafen may affect non-target soil fauna via changes in their microbiota and physiological indices, thereby contributing new knowledge regarding the adverse impacts of fomesafen on the terrestrial ecosystem.

Residues and dietary intake risk assessments of clomazone, fomesafen, haloxyfop-methyl and its metabolite haloxyfop in spring soybean field ecosystem.

Soybean is an important oilseed crop, but weed can have a significant effect on soybean yield. Clomazone, fomesafen, and haloxyfop-methyl are high-efficacy herbicides, and the combination of these herbicides shows an ideal effect on weed control. However, the residues of these herbicides and their impacts on human health are still largely unknown. In the current study, a rapid, sensitive, and selective method using modified QuECHERS procedure combined with HPLC-MS/MS was established to detect these herbicides in soybean matrices. The limits of quantification were 0.01, 0.01 and 0.025 mg/kg for haloxyfop-methyl, haloxyfop and fomesafen, and 0.005, 0.005 and 0.0125 mg/kg for clomazone in green soybean, soybean grain, and straw, with the average recoveries ranging from 80% to 107%. The terminal residues of the target compounds were all below the corresponding limits of quantification. The dietary risk assessment showed that the risk quotient values were far below the acceptable human consumption levels.

Insight into metabolism pathways of pesticide fomesafen in rice: Reducing cropping and environmental risks.

Fomesafen (FSA) is widely used in soybean fields for weed control. However, the persisting characteristics of FSA in the agricultural soil or water may become a hidden danger causing environmental pollution and phytotoxicity to succession crops. In this study, the growth and physiological responses of rice to FSA were investigated. It was found that the growth of rice seedlings was obviously inhibited by FSA exposure especially at over 0.1 mg L-1. To gain an insight into the molecular mechanisms for the potential ecotoxicology, four libraries of rice roots and shoots exposed to FSA were created and subjected to the global RNA-sequencing (RNA-Seq) combined with HRLC-Q-TOF-MS/MS analytical technologies to comprehensively characterize the biochemical processes and catalytic reactions involved in FSA metabolism in rice. Compared with those without FSA, 499 and 450 up-regulated genes in roots and shoots with FSA were detected. Many of them were closely correlated with the tolerance to environmental stress, detoxification of xenobiotics and molecular metabolism process including cytochrome P450, glutathione S-transferases and acetyltransferase. A total of eight metabolites and fourteen conjugates in the reactive pathways of hydrolysis, substitution, reduction, methylation, glycosylation, acetylation, and malonylation were characterized by HRLC-Q-TOF-MS/MS. The relationship between the metabolized derivatives of FSA and enhanced expression the corresponding enzymatic regulators was established. This study will help understand the mechanisms and pathways of FSA metabolism and inspire the further research on FSA degradation in the paddy crops and environmental or health risks.

Effect of fomesafen on the embryonic development of zebrafish.

Fomesafen is widely used in agriculture and can be detected in the environment and agricultural products. Research on the developmental toxicity of fomesafen in animals is currently very limited. Here, we used zebrafish as an animal model to evaluate the toxicity of fomesafen in developing aquatic vertebrates and higher animals. From 6h to 72h following fertilization, exposure of zebrafish embryos to 5, 10 and 20 mg/L of fomesafen resulted in pericardial edema, a reduction in heart rate, shortening of body length, and yolk sac edema. Fomesafen reduced the number of immune cells such as neutrophils and macrophages, increased the expression of a number of inflammatory factors, induced the up-regulation of the oxidative stress response and apoptosis, and disrupted the activity of enzymes related to nerve development, which affected the motility of the embryos. In conclusion, the results provide new evidence for the comprehensive assessment of fomesafen toxicity in aquatic vertebrates.

Investigation of resistance mechanism to fomesafen in Amaranthus retroflexus L.

Amaranthus retroflexus L. is one of the most troublesome weeds in autumn-crop fields in Northeast China. In recent years, field applications of fomesafen have failed to control an A. retroflexus population in Heilongjiang Province, China. Therefore, in this study, experiments were conducted to determine the resistance of A. retroflexus to fomesafen and investigate the molecular basis of herbicide resistance. Whole-plant dose-response experiments showed that the resistant (R) population exhibited 41.8-fold resistance to fomesafen compared with the susceptible (S) population. Target-gene sequence analysis revealed an Arg-128-Gly substitution in the protoporphyrinogen oxidase (PPO) in the R population. The response of PPO2 transgenic Arabidopsis thaliana to fomesafen demonstrated that the Arg-128-Gly substitution conferred high resistance to fomesafen. Cross- and multiple-resistance analyses indicated that the R population was cross-resistant to lactofen and carfentrazone-ethyl but was sensitive to imazethapyr, thifensulfuron-methyl, atrazine, and glyphosate. This study indicated that the Arg-128-Gly substitution is the main reason for A. retroflexus resistance to fomesafen. To our knowledge, this is the first report of a target-site based mechanism for the resistance to a PPO-inhibiting herbicide in A. retroflexus.

Simultaneous Analysis and Dietary Exposure Risk Assessment of Fomesafen, Clomazone, Clethodim and Its Two Metabolites in Soybean Ecosystem.

A commercial formulation, 37% dispersible oil suspension (DOS) (fomesafen, clomazone, and clethodim), is being registered in China to control annual or perennial weeds in soybean fields. In this paper, a liquid chromatography tandem mass spectrometry method with QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation was developed for the simultaneous determination of fomesafen, clomazone, clethodim, and its two metabolites (CSO and CSO2) in soybean, green soybean, and soybean straw samples. The mean recoveries of our developed method for the five analytes in three matrices were ranged from 71% to 116% with relative standard deviations (RSDs) less than 12.6%. The limits of quantification (LOQs) were 0.01 mg/kg in soybean, 0.01 mg/kg in green soybean, and 0.02 mg/kg in soybean straw while the limits of detection (LODs) ranged from 0.018 to 0.125 µg/kg for these five analytes. The highest final residual amount of CSO2 in green soybean samples (0.015 mg/kg) appeared in Anhui, and the highest in soybean straw samples was 0.029 mg/kg in Guangxi, whilst the terminal residues of fomesafen, clomazone, clethodim and CSO were lower than LOQs (0.01 mg/kg) in all samples. Furthermore, these terminal residues were all lower than the maximum residue limits (MRLs) set by China (0.1 mg/kg for fomesafen and clethodim, 0.05 mg/kg for clomazone) at harvest. Additional chronic dietary risk was evaluated using a risk quotients (RQs) method based on Chinese dietary habits. The chronic dietary exposure risk quotients were 4.3 for fomesafen, 0.12 for clomazone, and 19.3 for clethodim, respectively, which were significantly lower than 100. These results demonstrated that the dietary exposure risk of fomesafen, clomazone, and clethodim used in soybean according to good agricultural practices (GAP) was acceptable and would not pose an unacceptable health risk to Chinese consumers. These results not only offer insight with respect to the analytes, but also contribute to environmental protection and food safety.

Effect of pH on the Hydrolytic Transformation of a New Mixture Formulation of Fomesafen and Quizalofop-ethyl in Water.

A hydrolytic transformation study was conducted in water of pH 4.0, 7.0 and 9.2 to evaluate the effect of pH on persistence of a new readymix formulation of fomesafen and quizalofop-ethyl. The water samples were fortified at 0.5 and 1 µg mL-1 levels and analysed at 0 (2 h), 1, 3, 7, 15, 30, 60, 90, 120, 150 days interval. Both the analytical methods were validated following SANTE guideline and found accurate based on average recovery of 80-100%, Relative standard deviation (RSD) < 20% and Coefficient of Determination (R2) 0.99. The dissipation of both the molecules was pH dependent and followed first order kinetics. Higher persistence of fomesafen was observed in alkaline pH as compared to neutral and acidic pH with half-life of 41.56-63.24 days, whereas higher stability of quizalofop-ethyl was observed in the water of acidic pH followed by neutral and alkaline pH with half-life of 1.26-8.09 days.

Dissipation of fomesafen in fumigated, anaerobic soil disinfestation-treated, and organic-amended soil in Florida tomato production systems.

BACKGROUND: Fumigated, anaerobic soil disinfestation-treated (ASD), and organic-amended soil management strategies have been investigated as potential methyl bromide (MBr) alternatives for controlling diseases, nematodes, and weeds in soil. Nutsedge and broadleaf weed control using fomesafen has been reported to be comparable to MBr in normal cropping systems. There is no information on the fate of fomesafen used in combination with alternative practices. In this study, the fate of fomesafen in these alternative systems was measured by liquid chromatography-tandem mass spectrometry (LC/MS-MS) following extraction using a modified Quick Easy Cheap Effective Safe (QuEChERS) method. RESULTS: The reported half-life (DT50 ) values for fomesafen in the top 15 cm of soil were from 62.9 to 107.3 days. The DT50 values in organic-amended soil were higher than in ASD-treated soil in the top 15 cm. For all treatments, reductions in concentrations were positively correlated with lower redox potentials and organic matter content. Some leaching of fomesafen into the 16-30 cm zone was observed in all treatments. CONCLUSIONS: The DT50 values in this study were generally higher than those reported in previous studies performed at different locations. Due to increased losses of the herbicide and subsequent reduction in weed control, fomesafen is likely not to be suitable for effective weed control in systems using ASD techniques employing composted poultry litter and molasses. Integration of fomesafen using composted yard waste 1 (CYW1) and Soil Symphony Amendment (SSA) may result in acceptable weed control. Given that the soil was very sandy and the pH was higher than the pKa, fomesafen might leach deeper than 30 cm, particularly with the use of chemical soil fumigants (CSFs). © 2019 Society of Chemical Industry.