Excellent Weed Control Research Articles

Optimizing herbicide types and concentrations: Crucial elements for achieving intensive cultivation of common buckwheat

An appropriate herbicide type and concentration is essential for effective weed management and enhancing crop yield. However, the optimal herbicide type and corresponding application concentration for controlling weeds in common buckwheat on the Loess Plateau region of Northwestern China remain unclear. To address this gap, experiments were conducted to investigate the effects of various herbicides on weed control, dry matter accumulation, and grain yield in common buckwheat, and to analyze the variances in weed control efficacy and grain yields of the optimal herbicides at different concentrations. The results showed that both metolachlor and quizalofop-P-ethyl demonstrated effective weed control with lower phytotoxicity. Dry matter accumulation was lower under metolachlor, with no significant differences observed among the post-emergence herbicide treatments. Importantly, metolachlor and quizalofop-P-ethyl promoted the allocation of dry matter to grains. Remarkably, metolachlor and quizalofop-P-ethyl increased the grain yield by 15.59% and 26.97%, respectively, compared to spraying an equivalent amount of water. Additionally, the m2.25, q0.9, and q1.2 treatments exhibited excellent weed control effectiveness. And the higher grainnumber per plant observed under m2.25, q0.9, and q1.2 contributed to the increase in grain yield. Consequently, m2.25, q0.9 and q1.2 increased the grain yield by 34.42%, 38.86% and 33.16%, respectively. These findings demonstrate that applying metolachlor and quizalofop-P-ethyl at 2.25 L ha−1 and 0.9 or 1.2 L ha−1 respectively, is beneficial for efficient weed management and yield enhancement in common buckwheat cultivation on the Loess Plateau region of Northwestern China. These studies provide important guidance for promoting common buckwheat cultivation in this region.

Two-Pass Weed Management Programs for Identity-Preserved Soybean

Weed management is a challenge in Identity-Preserved (IP) soybean in Ontario, Canada. Six experiments were established in southwestern Ontario, Canada during 2021 and 2022 to evaluate weed control and soybean yield with preemergence (PRE), early postemergence (EPOST), and PRE followed by (fb) late POST (LPOST) herbicide programs. At 8 weeks after LPOST herbicide applications, S-metolachlor/metribuzin, pyroxasulfone/sulfentrazone, and flumioxazin/metribuzin/imazethapyr applied PRE provided 7, 49, and 99% control of velvetleaf; 65, 98, and 100% control of green pigweed; 7, 8, and 82% control of common ragweed; 25, 68, and 98% control of common lambsquarters; 91, 77, and 89% control of barnyardgrass; and 62, 68, and 93% control of green foxtail, respectively. Imazethapyr + bentazon applied EPOST provided 91% control of velvetleaf; 91% control of green pigweed; 78% control of common ragweed; 95% control of common lambsquarters; 76% control of barnyardgrass; and 79% control of green foxtail. S-metolachlor/metribuzin, pyroxasulfone/sulfentrazone, and flumioxazin/metribuzin/imazethapyr applied PRE fb bentazon + fomesafen + quizalofop applied LPOST provided 61, 86, and 100% control of velvetleaf; 97, 99, and 100% control of green pigweed; 94, 88, and 99% control of common ragweed; 96, 98, and 100% control of common lambsquarters; 97, 95, and 97% control of barnyardgrass; and 97, 96, and 99% control of green foxtail, respectively. There was minimal and transient soybean injury (6% or less) with all PRE or EPOST herbicide treatments, however, S-metolachlor/metribuzin, pyroxasulfone/sulfentrazone, or flumioxazin/metribuzin/imazethapyr applied PRE fb bentazon + fomesafen + quizalofop LPOST caused up to 22% injury in soybean. Weed interference reduced soybean yield 40%. Weed interference with S-metolachlor/metribuzin and pyroxasulfone/sulfentrazone applied PRE reduced soybean yield 25 and 31%, respectively. Reduced weed interference with flumioxazin/metribuzin/imazethapyr applied PRE, imazethapyr + bentazon applied EPOST, and the two-pass programs of a PRE fb LPOST herbicide resulted in soybean yield that was similar to the weed-free control. This study concludes that there are many effective weed management programs in IP soybean; however, the two-pass weed control programs are recommended since they provide good to excellent weed control, minimize soybean yield loss from weed interference, and ensure the use of multiple herbicide modes of action which reduces the selection intensity for the evolution of herbicide-resistant weeds.

Controlled release herbicide formulation for effective weed control efficacy

Controlled release formulation (CRF) of herbicide is an effective weed management technique with less eco-toxicity than other available commercial formulations. To maximise the effectiveness of CRFs however, it is crucial to understand the herbicide-releasing behaviour at play, which predominately depends on the interaction mechanisms between active ingredients and carrier materials during adsorption. In this study, we investigated and modelled the adsorption characteristics of model herbicide 2,4-D onto two organo-montmorillonites (octadecylamine- and aminopropyltriethoxysilane-modified) to synthesise polymer-based CRFs. Herbicide-releasing behaviour of the synthesised CRF microbeads was then analysed under various experimental conditions, and weed control efficacy determined under glasshouse conditions. Results revealed that adsorption of 2,4-D onto both organo-montmorillonites follows the pseudo-second-order kinetics model and is predominately controlled by the chemisorption process. However, multi-step mechanisms were detected in the adsorption on both organoclays, hence intra-particle diffusion is not the sole rate-limiting step for the adsorption process. Both organoclays followed the Elovich model, suggesting they have energetically heterogeneous surfaces. Herbicide-releasing behaviours of synthesised beads were investigated at various pH temperatures and ionic strengths under laboratory and glasshouse conditions. Furthermore, weed control efficacy of synthesised beads were investigated using pot studies under glasshouse condition. Desorption studies revealed that both synthesised microbeads have slow releasing behaviour at a wide range of pHs (5–9), temperatures (25–45 °C), and ionic strengths. The results also revealed that synthesised microbeads have excellent weed control efficacy on different broad-leaf weed species under glasshouse conditions.

Weed Control Efficacy and Soil Activity of a New Promising Bioherbicide "WeedLock"

The development of plant-based bioherbicides has gained the interest of researchers and acceptability from the farmers to control weeds in order to reduce their overdependence on chemical herbicides. Therefore, this research investigated the efficacy and soil activity of WeedLock, a new plant-based bioherbicide. In the efficacy study, WeedLock was applied at 672.75, 1345.50 (recommended dose), 2691.00 L ha-1 over the untreated (control) on weeds in mixed- culture (Ageratum conyzoides L., Eleusine indica (L.) Gaertn., and Cyperus iria L). For soil activity, Zea mays L. seedlings were grown in different soil textures, namely clay, sand, sandy clay loam, and peat soil and WeedLock was applied to each soil type at 1345.50 L ha-1 with a pipette as a soil drench method. After 21 days, the plants were harvested, including roots and the soil in trays that were previously sprayed with WeedLock, and the trays were further maintained for 1, 2, 4, 8, 12 and 16 weeks, respectively, before new seedlings were grown on the same soil. WeedLock at 1345.50 L ha-1 showed severe injury on weeds and produced 98.15% weed control efficacy compared to untreated (control). For soil activity, WeedLock did not show any significant decrease in growth and development of Z. mays, and the injury scale was 1.00, which means all leaves of Z. mays remained green, and the plants were actively growing on the WeedLock treated soils. Thus, it can be concluded that WeedLock has excellent weed control efficacy with soil activity.

Soil Solarization as an Alternative Weed Control Method for Archaeological Sites in the Mediterranean Region

Weed species commonly colonize archaeological sites in the Mediterranean region, which poses many issues for the sites’ function and the state of preservation of the monuments. Soil solarization was investigated as an alternative environmentally friendly weed control strategy following legislative limits on the use of herbicides at archaeological sites in Greece. The aim of the study was to evaluate the effectiveness of solarization applied during: (a) summer (the hottest season, as applied in organic and integrated agriculture) and (b) autumn (a season of low tourist activity in archaeological sites), testing two types of plastic mulching: (a) clear and (b) opaque black, and two types of soil preparation: (a) with tillage (as in the agricultural practice of the method) and (b) without tillage. Visual evaluation of the weed control rate suggested that the application of soil solarization during summer resulted in excellent weed control, 100% the following October to December period and over 90% until February. The application of soil solarization during autumn also provided excellent weed control and treatments with clear plastic and tillage resulted in complete (100%) weed control from October to December, while the following month weed control was over 90%. In late March, dry weight of weed biomass was significantly affected by the solarization treatments and it was significantly reduced by treatments with clear plastic. Thus, soil solarization is a sustainable method that has the potential to be used effectively for weed management in archaeological sites of the Mediterranean region. Even treatments without tillage generated excellent weed control during the winter weed flush period and are recommended to protect unexcavated, fragile artifacts. Also, the results of autumn treatments encourage the application of the method during the season of low tourist activity at archaeological sites.

Photodegradation of the Novel Herbicide Pyraquinate in Aqueous Solution: Kinetics, Photoproducts, Mechanisms, and Toxicity Assessment.

Pyraquinate, a newly developed 4-hydroxyphenylpyruvate dioxygenase class herbicide, has shown excellent control of resistant weeds in paddy fields. However, its environmental degradation products and corresponding ecotoxicological risks after field application remain ambiguous. In this study, we systematically investigate the photolytic behaviors of pyraquinate in aqueous solutions and in response to xenon lamp irradiation. The degradation follows first-order kinetics, and its rate depends on pH and the amount of organic matter. No vulnerability to light radiation is indicated. Ultrahigh-performance liquid chromatography with quadrupole-time-of-flight mass spectrometry and UNIFI software analysis reveals six photoproducts generated by methyl oxidation, demethylation, oxidative dechlorination, and ester hydrolysis. Gaussian calculation suggests that activities due to hydroxyl radicals or aquatic oxygen atoms caused these reactions on the premise of obeying thermodynamic criteria. Practical toxicity test results show that the toxicity of pyraquinate to zebrafish embryos is low but increases when the compound is combined with its photoproducts.

Response of Lowland Rice as Affected by Seedling Age and Time of Weed Control in Sudan Savana of Nigeria

An experiment was conducted at the Research and Training Farm of Federal College of Horticulture Gombe State (10020’N and 10030’E) during the 2021 rainy season in the Sudan Savanah agro-ecological zone of Nigeria. The aim of the research is to evaluate the effect of seedling age and time of application of post-emergence herbicide on the growth and yield of lowland rice (Faro 44). The experiment consisted of two factors, namely:- seedling age ( 3, 4, and 5-week-old seedlings) and time of weed control by post-emergence herbicide at 2, 3, and 4 weeks after transplanting. Farmer's practice hoes weeding, 7 weeks after transplanting as check and controls i.e. no weeding). These treatments were factorial combined (3 x 5) to give 15 treatment combinations of treatment and replicated thrice. The seedling was allocated to the main plot while weed control was to the sub-plot. Data gathered on weed, growth, yield, and yield attributes were subjected to analysis of variance, and mean differences were separated using Student Newman keuls (SNK ) at p< 0.05. The result revealed significant differences due to seedling age and time of weeding in most characters measured. Generally, the 3-week-old seedling (3WOS) performed better but at par with 4WOS, while earlier application of herbicides at 2 weeks after transplanting (WAT) gave excellent weed control. The highest yield of paddy rice 8849.4 and 9517.2 kg/ha, was obtained from 2WOS and herbicide application at 2WAT. It can be concluded that 3-4WOS seedlings of Faro 44 variety of rice and early application of herbicide at 2wat can be suggested to the rice farmers in the study area.

Impact of Chemical Weed Management Practices on Yield, Nutrient Uptake and Balance in Soil of High Density Planting Cotton in Deep Vertisols

In order to assess Clomazone 50 EC's effectiveness on seed cotton yield, nutrient uptake, and balance in HDPS cotton in deep Vertisols of the Northern Karnataka region, a field experiment was carried out in 2017–18 and 2018–19. The recommended course of treatment includes pre-emergence applications of Clomazone 50 EC at 250, 500, and 750 g a.i./ha compared to pendimethalin 37.5 CS@680 g a.i./ha, post-emergence applications of pyrithiobac sodium 10 EC and quizalofop ethyl hand weeding at 25 DAS and intercultivation at 50 and 75 days after sowing, as well as weed free. The experiment was set up using a randomised block design with triple replication. The application of Clomazone 50 EC @ 250 g a.i./ha was found to be effective in weed control and enhanced seed cotton yield (38.5%), according to the results. It led to excellent weed control, decreased nitrogen uptake by weeds, and increased nutrient uptake by the crop. Additionally, it leads to the least amount of nutrient losses in terms of uptake and losses. In order to effectively manage weeds in cotton, it was observed that Clomazone 50 EC @ 250 g a.i/ha, followed by pyrithiobac sodium 10 EC @ 75 g a.i./ha + Quizalofop ethyl 5 EC @ 75 g a.i./ha at 25 DAS, were the best applications.

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.

PRE AND POST CONTROL OF WEEDY RICE AND SELECTED RICE WEEDS WITH PREMIX OF IMAZAPIC AND IMAZAPYR AT DIFFERENT RATIOS

Field experiments were conducted in the rice fields of the Malaysian Agricultural Research and Development Institute in 2018 and 2019, to determine the efficacy of two commercial premix herbicides consisting of imazapic and imazapyr at 70:30 (formulation 1) and 30:70 (formulation 2) applied singly or in sequence for control of weedy rice and other rice weeds. Formulation 1 was applied as PRE at the 0 to 1-leaf stage of weedy rice while formulation 2 was applied as POST at the 3 to 4-leaf stage of weedy rice. Formulation 1 applied PRE at 150 g ai ha-1 with or without sequential application of formulation 2 applied POST at 75 or 150 g ai ha-1 provided complete inhibition of weedy rice. The same rate of formulation 1 applied PRE highly reduced weed density and dry weight of Monochoria vaginalis (99%) and Fimbristylis quinquangularis (93%) as compared to weedy check plots. Formulation 2 applied POST at 150 g ai ha-1 providing lower weed density and dry weight reduction of weedy rice (59 to 65%), M. vaginalis (80 to 81%), and F. quinquangularis (56 to 64%) as compared to those observed in formulation 1 applied PRE at 150 g ai ha-1. These results suggest that although formulations 1 and 2 share the same active ingredients, excellent control of weedy rice and rice weeds could only be achieved with PRE application of formulation 1 at 150 g ai ha-1.

Design, Synthesis, and Herbicidal Activity of Thioether Containing 1,2,4-Triazole Schiff Bases as Transketolase Inhibitors

Transketolase (TK) represents a potential target for novel herbicide development. To discover novel TK inhibitors with potency against resistant weeds, 36 thioether compounds containing 1,2,4-triazole Schiff bases were designed and synthesized for herbicidal activity evaluation. The results demonstrated that compounds 5av and 5aw provided excellent weed control with inhibition of over 90% against the tested weeds, even at concentrations as low as 100 mg/L in vitro. In addition, compounds 5av and 5aw exhibited higher postemergence herbicidal activity than all of the positive controls against the tested weeds at 50-90 g [active ingredient (ai)]/ha in a greenhouse, while being safe for crops of maize and wheat at 90 g (ai)/ha. Fluorescent binding experiments of At TK indicated that compounds 5av and 5aw had strong TK inhibitory activity and could tightly bind with the enzyme At TK. Also, molecular docking analyses revealed that the structures of compounds 5av and 5aw were suitable for TK inhibitory activity. Taken together, these results suggested that compounds 5av and 5aw were promising herbicide candidates for weed control in wheat and maize fields targeting TK.

Discovery of N-Phenylaminomethylthioacetylpyrimidine-2,4-diones as Protoporphyrinogen IX Oxidase Inhibitors through a Reaction Intermediate Derivation Approach.

Protoporphyrinogen oxidase (PPO, EC 1.3.3.4) is an effective target for green herbicide discovery. In this work, we reported the unexpected discovery of a novel series of N-phenylaminomethylthioacetylpyrimidine-2,4-diones (2-6) as promising PPO inhibitors based on investigating the reaction intermediates of our initially designed N-phenyluracil thiazolidinone (1). An efficient one-pot procedure that gave 41 target compounds in good to high yields was developed. Systematic Nicotiana tabacum PPO (NtPPO) inhibitory and herbicidal activity evaluations led to identifying some compounds with improved NtPPO inhibition potency than saflufenacil and good post-emergence herbicidal activity at 37.5-150 g of ai/ha. Among these analogues, ethyl 2-((((2-chloro-4-fluoro-5-(3-methyl-2,6-dioxo-4-(trifluoromethyl)-3,6-dihydropyrimidin-1(2H)-yl)phenyl)amino)methyl)thio)acetate (2c) (Ki = 11 nM), exhibited excellent weed control at 37.5-150 g of ai/ha and was safe for rice at 150 g of ai/ha, indicating that compound 2c has the potential to be developed as a new herbicide for weed management in paddy fields. Additionally, our molecular simulation and metabolism studies showed that the side chains of compound 2c could form a hydrogen-bond-mediated seven-membered ring system; substituting a methyl group at R1 could reinforce the hydrogen bond of the ring system and reduce the metabolic rate of target compounds in planta.

Bio-efficacy of sequential herbicide application for weed management in dry direct seeded rice

Weeds are the major biotic constraint in dry-direct seeded rice (DDSR), mainly due to the concurrent emergence and absence of water layer to suppress weeds. Therefore, strategy needs to be developed to get broad-spectrum weed control in DDSR. Experiments were conducted in rice (var. MTU 1010) during 2015-16 where sequential applications of pre- and post-emergence herbicides were evaluated for providing broad-spectrum weed management options in DDSR. Both the years, employing two-hand weedings at 15 and 30 DAS provided the lowest weed densities and weed dry weight at 75 DAS, whereas the maximum values of weeds were recorded in un-weeded plots. Among the herbicide-based weed management practices, application of pendimethalin 1000 g/ha fb bispyribac sodium 25 g/ha fb fenoxaprop 60 g/ha + chlorimuron + metsulfuron 4 g/ha at 30 DAS provided excellent weed control at 75 DAS, with 4.3% higher rice grain yield than two hand weedings at 15 and 30 DAS, pendimethalin 1000 g/ha fb bispyribac sodium 25 g/ha also provided good weed control and higher grain yield. Un-weeded plots noticed with considerable yield reduction of 79.5-83.3% over two hand weedings. Therefore, sequential application of pendimethalin 1000 g/ ha fb bispyribac sodium 25 g/ha is recommended along with need-based application of post-emergence herbicides (fenoxaprop 60 g/ha + chlorimuron + metsulfuron 4 g/ha) or one hand weeding to improve the weed control efficiency and provides economically higher productivity in DDSR.

Weed control with preemergence Ametryn in Arracacia xanthorrhiza

Two experiments were performed from 1985 to 1987 at Barranquitas in a Humatas soil to evaluate Ametryn (Evik 80 W) for preemergence control of weeds in Peruvian carrot or arradacha (Arracacia xanthorrhiza Banc). Five treatments were evaluated: Ametryn at 4.98, 8.97 and 17.94 kg ai/ha; a hand-weeded check (hoeing); and non-weeded check. There were significant differences (P ± 0.05) in the yield of commercial roots in the first experiment only between the non-weeded plots (7.00 t/ha) and Ametryn plots at 8.97 kg ai/ha (21.68 t/ha) whereas in the second trial, differences were observed between the hand-weeded (14.18 t/ha) and the non-weeded plots (4.11 t/ha). A considerable reduction in the second experiment was probably due to the fact that plants were harvested two months earlier (at 7 months) than in the first experiment, and some root damage was due to rats. Mean yields were 16.68 and 9.78 t/ha of commercial roots in experiments 1 and 2, respectively. These results showed that weed competition can reduce yields in arracacha by more than 60%. Good to excellent weed control with Ametryn was obtained at 12 weeks, when the arracacha foliage should have covered all soil surface area. There was 35% (first experiment) and 0.53% (2nd experiment) of weed coverage in the plots where Ametryn was applied at the lowest rate, 4.48 kg ai/ha. Herbicide efficiency increased with higher rates in both experiments. No toxic effects on the plants were observed from evaluations made 4 and 8 weeks after the treatments. Data obtained from these experiments showed that Ametryn was highly efficient in controlling weeds in arracacha up to 12 weeks even at the lowest application rate. The information obtained is valuable for obtaining registration of this pesticide for this crop.

Dissipation behaviour and dietary risk assessment of tembotrione in corn from Henan and Jilin Provinces, China

ABSTRACT The new triketone herbicide, tembotrione, provides excellent weed control in corn fields. To evaluate its safety, we established a modified QuEChERSpretreatment and ultra-high performance liquid chromatography-mass spectrometry method, using acetonitrile with 2% formic acid as the extractant and C18 as absorbent. The dissipation dynamics of tembotrionein corn straw and the terminal residual levels in all three corn matrices were studied in Henan and Jilin provinces. The linearity was excellent in the range of 0.01 to1 mg L−1, with the determination coefficient (R2) ≥0.9954. The average recovery was between 74% and 117%, with intra-day relative standard deviation less than 18.9 and the inter-day relative standard deviation less than 17.5. The degradation dynamic experiment showed that tembotrione decreased over time and followed the first-order kinetic equation. Our results showed that the regression coefficients of the dynamic equations were 0.9906 and 0.9897, with half-lives of 0.7 and 0.8 d, respectively. The final residue results showed that the maximum residues of tembotrione detected in corn in Jilin and Henan were 0.041 and 0.051 mg kg−1, respectively. The risk quotient (RQ) were calculated as 0.186 and 0.246, both of which were less than 1, which indicated an acceptable risk.

Drp1-mediated mitochondrial fission contributes to mitophagy in paraquat-induced neuronal cell damage.

Paraquat (PQ) is one of the most widely used herbicides in the world due to its excellent weed control effects. Accumulating evidence has revealed that long-term exposure to PQ can significantly increase the risk of Parkinson's disease (PD). However, the underlying molecular mechanisms are yet to be fully understood. Hence, we investigated the potential role of reactive oxygen species (ROS) and dynamin-related protein 1 (DRP1) in PQ-induced mitophagy, aiming to elaborate on possible molecular mechanisms involved in PQ-triggered neurotoxicity. Our results showed that ROS were increased, mitochondrial membrane potential was decreased at 100, 200, and 300μM PQ concentrations, and autophagy pathways were activated at a concentration of 100μM in neuronal cells. In addition, excessive mitophagy was observed in neurons exposed to 300μM PQ for 24h. Then, ROS-mediated mitochondrial fission was found to contribute to PQ-induced excessive mitophagy. Moreover, all aforementioned changes were significantly ameliorated by mdivi-1. Thus, our findings provide a novel neurotoxic mechanism and reveal the DRP1-mitochondrial fission pathway as a potential target for treatments of PQ-induced excessive mitophagy, serving as an alternative target for the prevention and treatment of Parkinson's disease. Because harmful substances are transmitted and enriched in the food chain, the toxic effect of environmental paraquat is nonnegligible, and more investigations are needed.

Design, Synthesis, and Molecular Mechanism Studies of N-Phenylisoxazoline-thiadiazolo[3,4-a]pyridazine Hybrids as Protoporphyrinogen IX Oxidase Inhibitors.

Protoporphyrinogen oxidase (PPO, EC 1.3.3.4) is an important target for green agrochemical discovery. Herein, a novel N-phenylisoxazoline-thiadiazolo[3,4-a]pyridazine herbicidal active scaffold was designed by the scaffold hybridization strategy. Systematic structural optimization enabled the discovery of a series of derivatives with excellent weed control at 9.375-150 g ai/ha by the post-emergent application. Some derivatives exhibited improved Nicotiana tabacum PPO (NtPPO)-inhibitory activity than fluthiacet-methyl. Of these, 2b, with Ki = 21.8 nM, displayed higher weed control than fluthiacet-methyl at the rate of 12-75 g ai/ha, and selective to maize at 75 g ai/ha. In planta, 2b was converted into a bioactive metabolite 5 (Ki = 4.6 nM), which exhibited 4.6-fold more potency than 2b in inhibiting the activity of NtPPO. Molecular dynamics simulation explained that 5 formed stronger π-π interaction with Phe392 than that of 2b. This work not only provides a promising lead compound for weed control in maize fields but is also helpful to understand the molecular mechanism and basis of the designed hybrids.

Herbicide effect on weed control, soil health parameters and yield of Egyptian clover (Trifolium alexandrinum L.)

Weeds are the major pests of forage production in India. An herbicide program is necessary for effective weed control in Egyptian clover (Trifolium alexandrinum L.). The study was conducted in 2013 and 2014 (two years) with an aim to evaluate the response of Egyptian clover and weeds to different herbicides that were being used in various cropping systems in Uttar Pradesh, India. Weed density and biomass, phytotoxicity of herbicides on crop, chlorophyll and carotenoid content in crop samples, root nodulation, soil dehydrogenase activity, soil microbial activity and herbicides effect on dry fodder yield were evaluated. Seventeen (three grasses, and 14 broadleaves) different weed species were observed in this study. Anagallis arvensis L., Cichorium intybus L., Cynodon dactylon (L.) Pers., Dactyloctenium aegyptium (L.) Wild. and Phalaris minor Retz. were the dominant weed species during the crop season. Among herbicides, Alachlor PRE and Imazethapyr PRE decreased grass weeds by 72% and 75% respectively, compared to weedy check, with no injury to crop at 25 days after sowing (DAS). However, alachlor PRE has controlled 64% more broadleaf weeds compared to Imazethapyr. At 50 DAS, imazethapyr POST, alachlor PRE fb quizalofop-ethyl POST provided excellent control of weeds, and resulted in yield equivalent to non-treated weed free check. Further, alachlor (PRE) fb quizalofop-ethyl (POST) and imazethapyr (POST) were selective herbicides on Egyptian clover (very slight to slight injury), recorded greatest nodule number (23–38 plant−1) and soil microbial community compared to other herbicide treatments. For grass weeds, propaquizafop provided effective control but had phytotoxic effect on the crop. In current scenario, where alachlor has been banned, application of either imazethapyr PRE/POST or imazethapyr PRE fb quizalofop-ethyl POST could be the potential herbicide options for control of weeds and obtaining higher yield of Egyptian clover.

Effect of Integrated Weed Management on Coffee Growth and Yield at Metu and Haru in South west and West Ethiopia

A field experiment was conducted to evaluate different single and integrated weed management methods on the growth and yield of coffee at Metu and Haru sub centers of Jimma Agricultural Research Center (JARC) between 2014-2018 cropping seasons. At Metu eight treatments were compared in randomized complete block design with three replications. The treatments included the following: (T1) One slash in May + one slash in August,(T2) Three slashing (May+Jully+Augesst), (T3) Roundup 3L/ha. sprayed in may followed by one slashing in July followed by vetivar grass mulching in September , (T4) Roundup 3L/ha.sprayed in May followed by soybean intercropping in July followed by mulching in September , (T5) Roundup 3L/ha. sprayed in May haricot bean intercropping in June followed by mulching in September , (T6) Roundup 3L/ha (only for the first year) Desmodium cover crop all year round permanently , (T7) Vetch cover crop in June followed with one hand weeding , and (T8). Weed free (plots kept weed free all year round). At Haru nine treatments were compared in randomized complete block design with three replications. The treatments included: (T1)one to two times slashing (farmers practice), (T2) three slashing in May, June and July, (T3) four slashing in May, June, July and August, (T4) Round up 3L/ha. sprayed in May followed by slashing followed by mulching followed by slashing and followed by mulching: (T5) slashing followed by Roundup 3L/ha. followed by coffee husk mulching: (T6) Roundup 3L/ha followed by desmodium cover cropping: (T7) Roundup 3L/ha followed by vetch cover cropping: (T8) Roundup 3L/ha followed by soybean intercropping followed by mulching: and (T9) Weed free (plots kept weed free all year round).. The result raveled that at both locations the major weed species included perennial sedges, perennial grasses, and annual broad leaf At Metu herbicide followed by soybean intercropping and followed by mulching in September gave a mean yield of 13.6 quintal clean coffee. Similarly, desmodium cover cropping provided excellent weed control and resulted in mean yield of 13.7 q/ha clean coffee .Desmodium showed a high smothering effect of the highly competitive perennial sedges and grasses by inhibiting the incoming light reaching the soil compared with other treatments and the weed free treatment.. At Haru Roundup 3L/ha followed by slashing followed by mulching followed by slashing and followed by mulching gave consistently very high coffee yield with a mean yield of 21 quintal /ha. compared with other treatments. The weed free treatment gave low yield at both locations. Vetch and desmodium did not well established at Haru compared with Metu. DOI: 10.7176/DCS/10-7-02 Publication date: July 31 st 2020

Synergistic mutations of two rapeseed AHAS genes confer high resistance to sulfonylurea herbicides for weed control.

A double mutant 5N of rapeseed was obtained with a synergistic effect of high resistance to sulfonylurea herbicide. Excellent weed control was observed in Ning R201 created by 5N resources. Sulfonylurea herbicides, which inhibit acetohydroxyacid synthase (AHAS), have become the most widely used herbicides worldwide. However, weed control in rapeseed crop production remains challenging in China due to the shortage of available herbicide-resistant cultivars. In this study, we developed a rapeseed line (PN19) with sulfonylurea herbicide resistance through seed mutagenesis. Molecular analysis revealed a Trp-574-Leu mutation in BnAHAS1-2R of PN19 according to the sequence of Arabidopsis thaliana, and an allele-specific cleaved amplified polymorphic sequence marker was developed to target the point mutation. A double mutant (5N) with very high sulfonylurea resistance was then created through pyramiding two mutant genes of PN19 and M342 by molecular marker-assisted selection. Herbicide resistance identification, toxicology testing, and an in vitro enzyme activity assay of AHAS in 5N indicated that each mutant was four and eight times more resistant to sulfonylurea than M342 and PN19, respectively. Protein structure analysis of AHAS1 demonstrated that the leucine of mutant Trp-574-Leu destroyed the original π-plane stacking effect of the local region for tribenuron-methyl binding, leading to herbicide tolerance. Isobole graph analysis showed a significant synergistic effect of the combination of two mutant genes in 5N for improved tolerance to sulfonylurea herbicides. Finally, we bred rapeseed variety Ning R201 using 5N herbicide resistance resources, and observed excellent weed control performance. Together, these results demonstrate the practical value of 5N application for optimizing and simplifying rapeseed cultivation in China.