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Chlorimuron-ethyl is currently the primary herbicide used for chemical weed control in a soybean field. In this study, a solid microbial inoculum (corn stalk-white rot fungus (W-1)) was prepared for the remediation of farmland soil contaminated by chlorimuron-ethyl. Firstly, the preparation method of the microbial inoculum was studied. Secondly, the degradation rate of the chlorimuron-ethyl in the ground by the solid microbial inoculum is improved by optimizing the proportion of the protective agent. Then the effects of applying solid microbial inoculum, free bacteria and corn straw on the degradation rate of chlorimuron-ethyl in soil were weighed. Finally, Illumina MiSeq sequencing was used to measure the composition and diversity of bacterial and fungal communities in the ground before and after using microbial inoculum. The degradation rate of chlorimuron-ethyl in soil by solid microbial inoculum was 84.87% after 20 d using corn straw as the support, room temperature drying, 4% Ca3(PO4)2 as the protective drying agent, and 1%(w) dextrin as the ultraviolet protective agent. Inoculation of white rot fungi could significantly affect the community structure of bacteria and fungi in the soil, making the chlorimuron-ethyl degrading communities become the dominant communities and playing an essential role in the degradation of chlorimuron-ethyl. The results showed that using solid microbial inoculum was an effective way to repair farmland soil polluted by chlorimuron-ethyl.

Glyphosate-resistant (GR) Palmer amaranth is a problematic, annual broadleaf weed in soybean production fields in Nebraska and many other states in the United States. Soybean resistant to 2,4-D, glyphosate, and glufosinate (Enlist E3™) has been developed and was first grown commercially in 2019. The objectives of this research were to evaluate the effect of herbicide programs applied PRE, PRE followed by (fb) late-POST (LPOST), and early-POST (EPOST) fb LPOST on GR Palmer amaranth control, density, and biomass reduction, soybean injury, and yield. Field experiments were conducted near Carleton, NE, in 2018, and 2019 in a grower's field infested with GR Palmer amaranth in 2,4-D–, glyphosate-, and glufosinate-resistant soybean. Sulfentrazone + cloransulam-methyl, imazethapyr + saflufenacil + pyroxasulfone, and chlorimuron ethyl + flumioxazin + metribuzin applied PRE provided 84% to 97% control of GR Palmer amaranth compared with the nontreated control 14 d after PRE. Averaged across herbicide programs, PRE fb 2,4-D and/or glufosinate, and sequential application of 2,4-D or glufosinate applied EPOST fb LPOST resulted in 92% and 88% control of GR Palmer amaranth, respectively, compared with 62% control with PRE-only programs 14 d after LPOST. Reductions in Palmer amaranth biomass followed the same trend; however, Palmer amaranth density was reduced 98% in EPOST fb LPOST programs compared with 91% reduction in PRE fb LPOST and 76% reduction in PRE-only programs. PRE fb LPOST and EPOST fb LPOST programs resulted in an average soybean yield of 4,478 and 4,706 kg ha–1, respectively, compared with 3,043 kg ha–1 in PRE-only programs. Herbicide programs evaluated in this study resulted in no soybean injury. The results of this research illustrate that herbicide programs are available for the management of GR Palmer amaranth in 2,4-D–, glyphosate-, and glufosinate-resistant soybean. Nomenclature: 2,4-D chlorimuron-ethyl; cloransulam-methyl; flumioxazin; glufosinate; glyphosate; imazethapyr; metribuzin; pyroxasulfone; saflufenacil; sulfentrazone; Palmer amaranth; Amaranthus palmeri S. Watson; soybean; Glycine max (L.) Merr.

Fleabane (Conyza spp.) is an important weed in grain production systems and is currently one of the most problematic weeds in Brazil. An important factor related to weeds such as fleabane is the characteristic of herbicide-resistant biotypes developed under selection pressure, with multiple resistance previously detected for Conyza spp. Thus, the aim of this study was to demonstrate the multiple resistance of Conyza sumatrensis to the herbicides paraquat, glyphosate, and chlorimuron. From the F2 seeds of biotypes with suspected resistance to paraquat, glyphosate, and chlorimuron, dose-response greenhouse experiments were conducted for the three herbicides. Herbicides were applied when the plants had 6-8 leaves that were at a height of 8 cm. At the end of the evaluations, 28 days after application, multiple resistance to paraquat, glyphosate, and chlorimuron was observed, with resistance factors (RF50) for the control of 7.43, 3.58, and 14.35 and for the reduction of dry mass of 2.65, 2.79, and 11.31, respectively. All the established criteria for demonstrating new cases of weed resistance were met; thus, the first case worldwide of a Conyza species with resistance to herbicides with three different mechanisms of action was confirmed.

Field experiments were conducted from 2017 to 2019 to determine the tolerance of carinata to several preemergence and postemergence herbicides. Preliminary screenings identified herbicides that caused large variation on carinata injury, indicating the potential for selectivity. Dose-response field studies were conducted to quantify the tolerance of carinata to select herbicides. Diuron applied preemergence at rates of 280 g ai ha–1 or higher reduced carinata population density 54% to 84% compared to the nontreated control. In certain locations, clomazone applied preemergence caused minor injury with an acceptable level of carinata tolerance and only doses above 105 g ai ha–1 caused yield reductions. Napropamide doses of 2,856 g ai ha–1 or higher applied preemergence caused at least 25% injury to carinata; however, the damage was not severe enough to reduce yields. Simazine applied postemergence at rates above 1,594 g ai ha–1 caused 50% or more injury, resulting in yield losses ranging from 0% to 95% depending on location. Clopyralid applied postemergence at 2,512 g ai ha–1 caused 25% injury with relative yield reductions, which varied across locations. The present study identified clomazone and napropamide applied preemergence, and clopyralid applied postemergence as potential herbicides for weed control in carinata. In contrast, diuron, simazine, metribuzin, imazethapyr, and chlorimuron caused high levels of carinata mortality and can be used to control volunteer carinata plants in rotational crops. Nomenclature: chlorimuron; clomazone; clopyralid; diuron; imazethapyr; napropamide; simazine; carinata, Brassica carinata A. Braun.

The chlorimuron-ethyl-degrading bacterium LW3 was isolated from contaminated soil and identified by 16S rRNA gene sequencing as Pseudomonas sp. When chlorimuron-ethyl was provided as the sole nitrogen source, the degradation efficiency in liquid medium was about 81.0% after 7 days of inoculation with strain LW3. The effects of chlorimuron-ethyl concentration and temperature on biodegradation were examined. Two metabolites of degradation were analyzed by LC/MS. Based on the identified products, strain LW3 seemed to be able to degrade chlorimuron-ethyl by cleavage of the sulfonylurea bridge. The inoculation of strain LW3 to chlorimuron-ethyl-treated soil resulted in a higher degradation rate than in uninoculated soil, regardless of the soil being sterilized or nonsterilized. This microbial culture has great potential for the bioremediation of soil contaminated with chlorimuron-ethyl.

Electroflotation (EF) is an electroanalytical technique applied for separating substances suspended in phase and is reported to be efficient for effluents and wastewater treatments. To date, there are no studies employing EF for the treatment of wastewater containing toxic organic compounds. In the present study, EF was tested as an electro-oxidative process to decontaminate wastewater containing the sulfonylurea herbicide chlorimuron-ethyl. To evaluate the value of EF, both the chemical and ecotoxicological efficacies were assessed in non-treated and treated wastewaters; the former monitored the herbicide and degradation products in the reaction medium through analytical chromatographic methods, whereas the latter comprised testing the 72 h growth of the green microalga Raphidocelis subcapitata and the 48 h lethality of the cladoceran Daphnia magna. Analysis by HPLC-UV allowed the monitoring of the electrochemical reaction, and a degradation mechanism based on gas chromatography–mass spectrometry was proposed. Despite the compromised herbicide structure, non-treated and treated wastewaters were similarly toxic for the microalgae Raphidocelis subcapitata and the invertebrate Daphnia magna. Even though EF did not remove the wastewater toxicity, the results indicate that toxic organic compounds are potentially oxidized by EF while signaling the need to combine chemical and ecotoxicological approaches to gauge the environmental sustainability of EF.

Research was conducted from 2015 to 2017 to investigate the potential for 2,4-D and multiple herbicide resistance in a waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] population from Missouri (designated MO-Ren). In the field, visual control of the MO-Ren population with 0.56 to 4.48 kg 2,4-D ha−1 ranged from 26% to 77% in 2015 and from 15% to 55% in 2016. The MO-Ren population was highly resistant to chlorimuron, with visual control never exceeding 7% either year. Estimates of the 2,4-D dose required to provide 50% visual control (I50) of the MO-Ren population were 1.44 kg ha−1 compared with only 0.47 kg 2,4-D ha−1 for the susceptible population. Based on comparisons to a susceptible population in dose–response experiments, the MO-Ren population was approximately 3-fold resistant to 2,4-D, and 7-, 7-, 22-, and 14-fold resistant to atrazine, fomesafen, glyphosate, and mesotrione, respectively. Dicamba and glufosinate were the only two herbicides that provided effective control of the MO-Ren population in these experiments. Examinations of multiple herbicide resistance at the individual plant level revealed that 16% of the plants of the MO-Ren population contained genes stacked for six-way herbicide resistance, and only 1% of plants were classified as resistant to a single herbicide (glyphosate). Results from these experiments confirm that the MO-Ren A. tuberculatus population is resistant to 2,4-D, atrazine, chlorimuron, fomesafen, glyphosate, and mesotrione, making this population the third 2,4-D–resistant A. tuberculatus population identified in the United States, and the first population resistant to six different herbicidal modes of action.

Palmer amaranth is the latest pigweed species documented in Connecticut; it was identified there in 2019. In a single-dose experiment, the Connecticut Palmer amaranth biotype survived the field-use rates of glyphosate (840 g ae ha-1) and imazaquin (137 g ai ha-1) herbicides applied separately. Additional experiments were conducted to (1) determine the level of resistance to glyphosate and acetolactate synthase (ALS) inhibitors in the Connecticut-resistant (CT-Res) biotype using whole-plant dose-response bioassays, and (2) evaluate the response of the CT-Res biotype to POST herbicides commonly used in Connecticut cropping systems. Based on the effective dose required for 90% control (ED90), the CT-Res biotype was 10-fold resistant to glyphosate when compared with the Kansas-susceptible (KS-Sus) biotype. Furthermore, the CT-Res biotype was highly resistant to ALS-inhibitor herbicides; only 18% control was achieved with 2,196 g ai ha-1 imazaquin. The CT-Res biotype was also cross-resistant to other ALS-inhibitor herbicides, including chlorimuron-ethyl (13.1 g ai ha-1), halosulfuron-methyl (70 g ai ha-1), and sulfometuron-methyl (392 g ai ha-1). The CT-Res Palmer amaranth was controlled 75% to 100% at 21 d after treatment (DAT) with POST applications of 2,4-D (386 g ae ha-1), carfentrazone-ethyl (34 g ai ha-1), clopyralid (280 g ae ha-1), dicamba (280 g ae ha-1), glufosinate (595 g ai ha-1), lactofen (220 g ai ha-1), oxyfluorfen (1,121g ai ha-1), and mesotrione (105 g ai ha-1) herbicides. Atrazine (2,240 g ai ha-1) controlled the CT-Res biotype only 52%, suggesting the biotype is resistant to this herbicide as well. Here we report the first case of Palmer amaranth from Connecticut with multiple resistance to glyphosate and ALS inhibitors. Growers should proactively use all available weed control tactics, including the use of effective PRE and alternative POST herbicides (tested in this study), for effective control of the CT-Res biotype. Nomenclature: 2, 4-D ester; atrazine; carfentrazone-ethyl; chlorimuron-ethyl; clopyralid, dicamba; glyphosate; glufosinate; halosulfuron-methyl; imazaquin; lactofen; mesotrione; oxyfluorfen, sulfometuron-methyl; Palmer amaranth, Amaranthus palmeri S. Watson

Pesticide pollution in recent times has emerged as a grave environmental problem contaminating both aquatic and terrestrial ecosystems owing to their widespread use. Bioremediation using gene editing and system biology could be developed as an eco-friendly and proficient tool to remediate pesticide-contaminated sites due to its advantages and greater public acceptance over the physical and chemical methods. However, it is indispensable to understand the different aspects associated with microbial metabolism and their physiology for efficient pesticide remediation. Therefore, this review paper analyses the different gene editing tools and multi-omics methods in microbes to produce relevant evidence regarding genes, proteins and metabolites associated with pesticide remediation and the approaches to contend against pesticide-induced stress. We systematically discussed and analyzed the recent reports (2015–2022) on multi-omics methods for pesticide degradation to elucidate the mechanisms and the recent advances associated with the behaviour of microbes under diverse environmental conditions. This study envisages that CRISPR-Cas, ZFN and TALEN as gene editing tools utilizing Pseudomonas, Escherichia coli and Achromobacter sp. can be employed for remediation of chlorpyrifos, parathion-methyl, carbaryl, triphenyltin and triazophos by creating gRNA for expressing specific genes for the bioremediation. Similarly, systems biology accompanying multi-omics tactics revealed that microbial strains from Paenibacillus, Pseudomonas putida, Burkholderia cenocepacia, Rhodococcus sp. and Pencillium oxalicum are capable of degrading deltamethrin, p-nitrophenol, chlorimuron-ethyl and nicosulfuron. This review lends notable insights into the research gaps and provides potential solutions for pesticide remediation by using different microbe-assisted technologies. The inferences drawn from the current study will help researchers, ecologists, and decision-makers gain comprehensive knowledge of value and application of systems biology and gene editing in bioremediation assessments.

Plants of Sumatran fleabane [Conyza sumatrensis (Retz.) E. Walker] were identified in a field with an unusual rapid leaf-injury herbicide symptoms after application of 2,4-D in mixture with glyphosate. The objectives of this study were to confirm the occurrence of resistance to 2,4-D herbicide and to characterize the occurrence of rapid necrosis as the mechanism associated with the herbicide resistance in C. sumatrensis. The studies performed were an initial screening, effect of 2,4-D alone and associated with glyphosate, cross- and multiple-resistance evaluation, effect of commercial formulation and analytical product, and rate of H2O2 evolution. The Marpr9-rn accession was identified with rapid necrosis symptoms and survival to 804 g ae ha–1 of 2,4-D. The resistance factor to the herbicide 2,4-D was 18.6 at 49 d after spraying. The analytical product 2,4-D and the commercial formulation resulted in similar symptoms of rapid necrosis. This symptom did not occur for the six other auxinic herbicides (dicamba, florpyrauxifen-benzyl, fluroxypyr, halauxifen-methyl, picloram, and triclopyr), indicating absence of cross-resistance. Multiple resistance to the herbicides paraquat, saflufenacil, and ammonium glufosinate was not identified in the Marpr9-rn population. However, survival following treatment with the herbicides glyphosate and chlorimuron-ethyl occurred. The evolution of H2O2 began at 15 min after application and was less pronounced in low light. These results indicate the first case of resistance to 2,4-D and occurrence of rapid necrosis in C. sumatrensis.