Effective Weed Control Research Articles

Simultaneous determination of triazine herbicides and their metabolites in shellfish by HPLC-MS/MS combined with Q/E-Orbitrap HRMS.

Triazine herbicides are used extensively in agriculture and aquaculture worldwide because of their broad effectiveness in weed control. However, after they are discharged into the sea, they seriously contaminate aquatic ecosystems and threaten aquatic organisms, especially shellfish. Currently, there are no established methods for the detection and confirmation of triazine herbicides and their metabolites in biological matrixes. Hence, the food safety of aquatic products cannot be accurately evaluated, which creates a technical barrier against international aquatic product trade. In this study, for the first time, a method was developed for the analysis and confirmation of seven triazine herbicides and 13 metabolites in shellfish, based on alkaline acetonitrile extraction and neutral Al2O3 cartridge purification coupled with internal standard calibration. Specifically, quantitative and qualitative analysis was conducted using high-performance liquid chromatography-triple quadrupole mass spectrometry (HPLC-MS/MS), and accurate identification was carried out by quadrupole orbitrap high-resolution mass spectrometry (Q/E Orbitrap HRMS). The results showed that target analytes demonstrated good linearity within the corresponding range (R2 > 0.995). The limit of detection and limit of quantitation of the proposed method were 0.1 and 0.3 μg/kg, respectively. The average recoveries of analytes were between 70.0% and 120% when spiked at three levels with blank oyster (Crassostrea gigas) as the matrix, and the relative standard deviations (RSDs) were all less than 12% (n=6). The proposed method was successfully applied for the detection of triazine herbicide residues in oyster samples during actual breeding, and the presence of DIP, HP, DEHA, and other metabolites in positive samples was confirmed by Q/E Orbitrap HRMS. This method exhibits high accuracy, high sensitivity, and good reproducibility. It has promising application prospects in the field of hazard analysis and the positive identification of aquatic products.

Emerging Strategies for the Bioremediation of the Phenylurea Herbicide Diuron.

Diuron (DUR) is a phenylurea herbicide widely used for the effective control of most annual and perennial weeds in farming areas. The extensive use of DUR has led to its widespread presence in soil, sediment, and aquatic environments, which poses a threat to non-target crops, animals, humans, and ecosystems. Therefore, the removal of DUR from contaminated environments has been a hot topic for researchers in recent decades. Bioremediation seldom leaves harmful intermediate metabolites and is emerging as the most effective and eco-friendly strategy for removing DUR from the environment. Microorganisms, such as bacteria, fungi, and actinomycetes, can use DUR as their sole source of carbon. Some of them have been isolated, including organisms from the bacterial genera Arthrobacter, Bacillus, Vagococcus, Burkholderia, Micrococcus, Stenotrophomonas, and Pseudomonas and fungal genera Aspergillus, Pycnoporus, Pluteus, Trametes, Neurospora, Cunninghamella, and Mortierella. A number of studies have investigated the toxicity and fate of DUR, its degradation pathways and metabolites, and DUR-degrading hydrolases and related genes. However, few reviews have focused on the microbial degradation and biochemical mechanisms of DUR. The common microbial degradation pathway for DUR is via transformation to 3,4-dichloroaniline, which is then metabolized through two different metabolic pathways: dehalogenation and hydroxylation, the products of which are further degraded via cooperative metabolism. Microbial degradation hydrolases, including PuhA, PuhB, LibA, HylA, Phh, Mhh, and LahB, provide new knowledge about the underlying pathways governing DUR metabolism. The present review summarizes the state-of-the-art knowledge regarding (1) the environmental occurrence and toxicity of DUR, (2) newly isolated and identified DUR-degrading microbes and their enzymes/genes, and (3) the bioremediation of DUR in soil and water environments. This review further updates the recent knowledge on bioremediation strategies with a focus on the metabolic pathways and molecular mechanisms involved in the bioremediation of DUR.

Weed Control and Tigernut Response to Preemergence Herbicides Applied at Transplanting

Tigernut (Cyperus esculentus var. sativus) is a type of sedge that is quickly becoming popular as a superfood. As demand for tigernut continues to increase, more information is needed to develop weed management strategies for the crop to maximize tuber yield and quality. However, no herbicide is currently labeled for use with tigernut. Experimental trials were conducted in 2017 and 2018 to assess crop safety and control of economically important weeds with preemergence herbicides for transplanted ‘NG3’ and ‘OG’ tigernut. Oxyfluorfen applied alone or mixed with pendimethalin provided excellent control (>85%) of smooth pigweed (Amaranthus hybridus), carpetweed (Mollugo verticillata), and large crabgrass (Digitaria sanguinalis), and it did not cause any tigernut injury, stunting, or yield reduction compared with the weed-free control. However, none of the treatments controlled hairy galinsoga (Galinsoga quadriradiata) satisfactorily 2 months after herbicide application. Bensulide alone or associated with oxyfluorfen caused 14% to 25% stunting of tigernut. Bensulide alone only provided short-term control of broadleaf weeds. Increased weed competition and tigernut phytotoxicity associated with bensulide resulted in a 39% reduction in tuber yield compared with oxyfluorfen alone. Finally, S-metolachlor caused up to 78% stunting and a 68% reduction in vegetative tigernut biomass (on average) compared with the weed-free control. Tuber yield was reduced 55% to 97% after S-metolachlor was applied at transplanting. Oxyfluorfen would provide effective weed control up to 8 weeks after treatment in fields where hairy galinsoga is not a weed of concern and fulfill the requirement of a weed-free period without affecting tuber yield of quality.

Selection of transgenic citrus plants based on glyphosate tolerance conferred by a citrus 5-enolpyruvylshikimate-3-phosphate synthase variant.

We have defined the conditions for citrus transformations using glyphosate as selection agent. This protocol results in high transformation rate and low incidence of chimeric shoots. Glyphosate, the most widely used herbicide in the world, specifically inhibits 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), an essential enzyme of the shikimate pathway. Various laboratory-generated or naturally evolved glyphosate-resistant EPSPS variants have been used to produce glyphosate-tolerant transgenic crops, enabling highly effective weed control in agriculture. In this study, we explored the potential of using a citrus EPSPS variant that mimics the previously reported Eleusine indica glyphosate-resistant TIPS (T102I + P106S) mutant for selection of transgenic citrus plants in the presence of glyphosate. We found that glyphosate did not suppress bud formation on 'Duncan' grapefruit seedling explants, but inhibited non-transgenic bud outgrowth to produce shoots in a concentration-dependent manner. At certain concentrations, glyphosate had dramatic effect on the transformation rate and the percentage of non-chimeric transgenic shoots in this newly developed selection system. Specifically, at 0, 10, 20, and 50 μM of glyphosate, the citrus TIPS EPSPS-based selection resulted in transformation rates of 4.02, 5.04, 14.46, and 40.78%, respectively, and 6.41, 23.96, 42.94, and 40.17% of non-chimeric transgenic shoots, respectively. These results indicate that the citrus TIPS EPSPS-glyphosate selection system is highly efficient and can be used as an alternative to antibiotic-based selection methods in citrus genetic transformation. Furthermore, the selection conditions defined in this study are expected to greatly facilitate the production of genetically modified, market-friendly citrus plants, such as cisgenic and intragenic plants.

Junglerice (<em>Echinochloa colona</em> L.) seedling emergence model as a tool to optimize pre-emergent herbicide application

Junglerice (Echinochloa colona), one of the worst and most problematic weeds globally, causes significant economic losses due to yield loss and control cost increase. Taking into account that this weed emerges in approximately five months - from September to January -, and considering that reducing herbicide use is key in the current intensification of agricultural production systems, the present study was carried out under the hypothesis that there should be an optimal moment for pre-emergent herbicide application to achieve maximum weed control effectiveness and efficiency. Therefore, experiments were carried out from August 2016 to January 2021 in Pergamino, Buenos Aires province, Argentina, using a double-logistic emergence model of junglerice seedlings. Bicyclopyrone plus s-metolachlor, clomazone, and pyroxasulfone plus saflufenacil were applied at different times between 92 and 478 growing degree days (GDDs). Single applications between 348 and 399 GDD were observed to reduce junglerice seedling emergence by 85-99%, depending on the herbicide used. Such a seedling emergence reduction could be a convenient strategy to provide significant weed suppression in the field in combination with a competitive crop and within a sustainable production system. The results of the present study lead to the conclusion that using predictive models for pre-emergent herbicide applications ensures more effective use of herbicides and reduces the amounts of herbicides used and the risks of selecting herbicide-resistant junglerice populations. Highlights - Weed occurrence indirectly increases the number of herbicide applications in Argentina. - Reducing the number and volume of herbicide applications contributes to mitigating environmental impact in the short term. - There is a critical time during weed emergence in which chemical control via herbicide application is most effective. - Seedling emergence models are useful management tools to predict critical timing for weed control.

Complementing cultural weed control with plant allelopathy: Implications for improved weed management in wheat crop

Wheat (Triticum aestivum L.) is an important cereal crop in Pakistan which is suffering from major grain production loss because of weed infestations. Control of weeds by herbicides is a primary weed management tool in wheat crop which can be detrimental to the environment and grain produce. Development of an efficient and eco-friendly alternate to the herbicidal weed control, testing the effectiveness of cultural weed control (crop row orientation, selected wheat genotypes and hand weeding) and plants water extracts was undertaken for weed control in wheat. An experiment was run under field conditions in winter season in 2016–2017 and in 2017–2018 in Khyber Pakhtunkhwa Province, Pakistan. The repeated experiment was each time undertaken using a randomized complete block design with a double split plot arrangements at the New Developmental Farm, University of Agriculture, Peshawar, Pakistan. The crop row orientations used were assigned to the main plots. The wheat genotypes used were assigned to the sub-plots. The allelopathic water extracts and hand weeding were assigned to the sub-sub plots. The averaged mean values for row orientations of both the years revealed lowest weed density (95.7 weeds m−2), highest grains per spike (47.3), 1000 grains weight (44.7 g) in north to south row orientation. The averaged mean values of weed density (101.6 weeds m−2), grains per spike (48.2), 1000 grains weight (45.9 g), crude protein content (12.793%), crude fat content (1.533%) and ash content (1.586%) were greater for the wheat genotype Pirsabaq-2013 and Atta-Habib-2010. Water extract of S. halepense, P. hysterophorus, H. annuus and hand weeding showed significantly lower weed density (84.0 to 93.3), grains per spike (50.9 to 48.3), 1000 grains weight (48.3 to 46.2 g), grains protein content (12.280 to 12.209%), grains crude fat content (1.471 to 1.464%) and grains ash content (1.523 to 1.515%). Interaction effect of different tested weed control treatments i.e. N-S × Pirsabaq-2013 and Atta-Habib-2010 × water extract of S. halepense, P. hysterophorus and H. annuus were found to show further reduction in weed density and enhance grains per spike and grains nutrition contributing parameters. Our results show that sowing wheat genotypes Pirsabaq-2013 and Atta-Habib-2010 in north-to-south row orientation, and application of water extract of S. halepense, P. hysterophorus, H. annuus can give an effective weed management and increased quality grain yield of wheat.

The Effect of Planting Density and Number of Hand Weeding Times on Weeds Control and Relationship Between Morphological Characteristics With Content and Yield of Essential Oil of Satureja Hortensis L.

The aim of this study was to evaluate the effect of planting density and number of weeding times on weeds control and the relationship between morphological characteristics with the content and yield of Satureja hortensis essential oil (EO). S. hortensis planting density at four levels (50, 75, 100 and 125 plants per m2) was the first factor and hand weeding in 4 times (2, 4, 6 and 8 weeks after planting- WAP), 3 times (2, 4 and 8 WAP), 2 times (4 and 8 WAP) and weedy check as second factor. Dominant weeds were included redroot pigweed (Amaranthus retroflex L.), black nightshade (Solanum nigrum L.) and lambsquarters (Chenopodium album L.) in this field. Increasing Satureja hortensis density under densities of 50, 75 and 100 plants per m2 with weeding especially four times, significantly increased the dry weight and content of EO and yield of this plant. But the delay in the weeding times, such as twice weeding, significantly reduced this trait. This indicates that weeding in S. hortensis should be done at the beginning of the growing season due to its slow growth. Also, increasing the density of S. hortensis from 100 to 125 plants per m2 intensifies competition, so that its EO yield content decreased despite increasing the number of weeding times compared to the weedy check. Overall, due to the favorable effect of weed control under three or four weeding times on dry weight and content and EO yield of S. hortensis, weeding at the mentioned times is recommended in Gonbad Kavous area and areas with similar conditions to Gonbad Kavous.

Dampak Aplikasi Mulsa terhadap Dominasi dan Pertumbuhan Gulma pada Edamame

Edamame was a commodity that contains all types of essential amino acids that can stabilize blood sugar levels, increase metabolism and energy levels, and help build muscle and immune system cells. Farmer’s interest in planting edamame is high due to the high demand and promising commodity prices. However, edamame is often faced with weed disturbances. The weeds in edamame cultivation can reduce production in quantity and quality. Research is needed for effective weed control techniques to reduce losses and increase production plus increasing income. The research was conducted at the Lampung State Polytechnic from April to September 2020. The study was arranged using a randomized block design with single factor treatment in the form of weed control techniques with 4 treatments and 3 replications. The aim of this research was to find the best weed control techniques in edamame cultivation. The results of this study were using mulch can reduce weed growth by 75.75% to 95.45% compared without using mulch. The highest pressure on weed growth was obtained from the used plastic mulch as a weed control technique.

Differential germination characteristics of glyphosate-resistant and glyphosate-susceptible Chloris virgata populations under different temperature and moisture stress regimes.

Thorough knowledge of the germination behavior of weed species could aid in the development of effective weed control practices, especially when glyphosate resistance is involved. A study was conducted using two glyphosate-resistant (GR) (SGW2 and CP2) and two glyphosate-susceptible (GS) (Ch and SGM2) populations of Chloris virgata, an emerging and troublesome weed species of Australian farming systems, to evaluate their germination response to different alternating temperature (15/5, 25/15 and 35/25°C with 12 h/12 h light/dark photoperiod) and moisture stress regimes (0, -0.1, -0.2, -0.4, -0.8 and -1.6 MPa). These temperature regimes represent temperatures occurring throughout the year in the eastern grain region of Australia. Seeds germinated in all the temperature regimes with no clear indication of optimum thermal conditions for the GR and GS populations. All populations exhibited considerable germination at the lowest alternating temperature regime 15/5°C (61%, 87%, 49%, and 47% for Ch, SGM2, SGW2, and CP2, respectively), demonstrating the ability of C. virgata to germinate in winter months despite being a summer annual. Seed germination of all populations was inhibited at -0.8 and -1.6 MPa osmotic potential at two alternating temperature regimes (15/5 and 35/25°C); however, some seeds germinated at 25/15°C at -0.8 MPa osmotic potential, indicating the ability of C. virgata to germinate in arid regions and drought conditions. Three biological parameters (T10: incubation period required to reach 10% germination; T50: incubation period required to reach 50% germination; and T90: incubation period required to reach 90% germination) suggested late water imbibition with increasing moisture stress levels. The GR population SGW2 exhibited a distinctive pattern in T10, T50, and T90, possessing delayed germination behaviour and thus demonstrating an escape mechanism against pre-plating weed management practices. Knowledge gained from this study will help in developing site-specific and multi-tactic weed control protocols.

Power on! Low-energy electrophysical treatment is an effective new weed control approach.

Environmental concerns are driving the call for adoption of alternative nonchemical weeding approaches. This study aimed to develop and evaluate a novel, precise, low-energy electrophysical treatment weeding systems and to provide new insight into their control mechanism. Two electrophysical treatment systems, based on AC (2.2 kV) and DC (40 kV) energy sources, were developed and evaluated. The impacts of various operational and biological factors on the weed control effectiveness were evaluated. Additionally, thermal images were taken during the treatments to document plant temperature. Treatments via direct leaf contact caused greater damage to Amaranth plants than the stem contact treatments, with 75% and 20% biomass reduction compared to control, respectively. Treatment of early growth stages was favorable over later growth stages, with 100% and 75% biomass reduction for Trifolium pretense plants treated with 0.0125 W h 2 and 4 weeks after seeding, respectively, compared to control. Additionally, the applied energy affected treatment performance, with its impact varying across the growth stages and species; at the two-leaf growth stage, 0.0025 W h treatment was sufficient for plant death. A >40 °C increase in plant temperature was measured during the electrophysical treatment, with the temperature of some plant organs reaching ~70 °C. Results from this study demonstrate the potential use of electrophysical treatment as an effective weed control tool. The low energetic demands in the new systems provide suitable control results when applied at early stages. Temperature increase seemed to be one of the main control factors, yet efficacy was affected by various biological factors.

Selective Action Mechanism of Fenclorim on Rice and Echinochloa crusgalli Is Associated with the Inducibility of Detoxifying Enzyme Activities and Antioxidative Defense.

Fenclorim (Fen) is a safener developed for pretilachlor (Pre) that can protect rice from injury caused by Pre but does not lower the weed control effects of Pre. Unfortunately, the mechanism of selective action of Fen between rice and weeds, such as Echinochloa crusgalli (barnyard grass), has not been clarified. In this study, the differences in physiology, biochemistry, and gene transcription between rice and E. crusgalli response to Fen were compared. Comparing the protection effects of Fen on plant growth, it was found that Fen significantly protected rice from Pre, but did not protect E. crusgalli. The detection of malondialdehyde (MDA) content and activities of antioxidant enzymes showed that Pre induced significant oxidative damage both in rice and E. crusgalli; however, Fen reduced oxidative damage in rice but not in E. crusgalli. Transcriptome analysis revealed that Fen induced more genes related to herbicide metabolism in rice than in E. crusgalli, especially the glutathione-S-transferase (GST) genes, with six upregulated in rice but no genes upregulated in E. crusgalli. Accordingly, the GST activity analysis showed that Fen increased the activity of rice instead of E. crusgalli. These results indicate that the elevation of detoxifying enzyme activities and antioxidative defense may be the mechanism of selective action of Fen in rice but not in E. crusgalli.

Reduced crop density increases floral resources to pollinators without affecting crop yield in organic and conventional fields

Abstract Effective weed control in agricultural crop fields increases yields, but simultaneously reduces floral resources for pollinators because many weed species provide pollen and nectar. Consequently, efforts to enhance crop yields on organic farms by using effective weed control methods risk compromising positive effects of organic farming on pollinating insects. Thus, it is important to find management strategies that alleviate the trade‐off between crop yields and flowering weeds on organic farms. We investigated the relationship between cereal yields, flowering weeds and bumblebees on organic and conventional arable land. We also investigated the potential of adjusting crop sowing density to benefit flowering weed species richness and floral resources to bumblebees without affecting crop yield. Floral resources and species richness of flowering weeds were higher in organic compared to conventional fields and were negatively related to crop yield in organic but not conventional fields (where the variation of floral resources and flowering weed species richness was comparatively low). Bumblebee species richness was higher in organic compared to conventional fields, and abundance was twice as high in organic as in conventional fields, but not significantly so. Yields in organic fields were two thirds of those in conventional fields. When simultaneously testing the effect of farming type (organic vs. conventional), crop yield and floral resources, only floral resources were related significantly to bumblebee abundance and species richness. A lower sowing density of the crop increased floral resources without negatively affecting crop yield. Synthesis and applications. We show that organic farming practices in cereals benefit bumblebees by allowing more flowering weeds, but at a cost in terms of lower yields. However, adjusting crop sowing density provides an opportunity to attain increased floral resources without negatively affecting crop yields. Thus, by increasing floral resources, adjusting crop sowing density may contribute to supporting high bumblebee densities, which in turn sustain pollination services to wild plants and insect‐pollinated crops, such as oilseed rape and field beans, in agricultural landscapes. We suggest that sowing strategies have the potential to contribute to ecological intensification by supporting organisms that provide ecosystem services to agriculture.

Influence of herbicides under biofertilizer application on fennel (Foeniculum vulgare) yield and quality with special reference to herbicide residues

BackgroundWeed occurrence and fertilization are considered two of the most factors influencing fennel yield. A two season’s field study was undertaken to investigate the response of fennel crop to two different herbicides under the application of biofertilizers. The two herbicides are pendimethalin (at reduced rate), fluazifop-p butyl and a combination of sequential application of both of them. The biofertilizers were used in 3 rates of 1:1:1, 2:1:1 and 1:1:2 (v/v/v) from atmospheric nitrogen-fixating, phosphorous-dissolving and potassium-solubilizing bacterial strains.ResultsThe results indicated that under all rates of the biofertilizers, the two herbicides applied individually caused significant reduction in growth parameters of the fennel plant estimated. Hand weeding (untreated check) increased fruit yield by 63% and oil yield by 78% compared to unweeded control, while sequential application of pendimethalin + fluazifop increased fruit yield by 45% and oil yield by 83% under biofertilizers at the rate of 2:1:1. Slight decrease in protein content using pendimethalin + fluazifop (12.94, and 12.96%) compared to 13.56% for hand weeding was observed. However, fluazifop alone showed no significant differences (13.63 and 13.13%) during both seasons under the biofertilizer rate of 2:1:1. No detectable residues of pendimethalin and fluazifop applied alone or sequentially were found in the analyzed dry seeds.ConclusionThe obtained results concluded that using proper level of biofertilizer combined with herbicides would increase the seed yield and oil content of fennel. Nevertheless, further investigation is needed to search for safer and effective weed control methods in medicinal plants.

Optimizing glyphosate tolerance in rapeseed by CRISPR/Cas9-based geminiviral donor DNA replicon system with Csy4-based single-guide RNA processing.

Rapeseed (Brassica napus L.) is an important oil crop worldwide, and effective weed control can protect its yield and quality. Farmers can benefit from cultivars tolerant to herbicides such as glyphosate. Amino acid substitutions in enolpyruvylshikimate-3-phosphate synthase (EPSPS) render the plant less sensitive to glyphosate. Therefore, we aimed to optimize the glyphosate tolerance trait in rapeseed via endogenous EPSPS modification. To achieve effective gene replacement in B. napus L., we employed a CRISPR/Cas9 system expressing single-guide RNAs (sgRNAs) cleaved by the CRISPR-associated RNA endoribonuclease Csy4 from Pseudomonas aeruginosa, for targeted induction of double-strand breaks. Both the donor template and a geminiviral replicon harbouring an sgRNA expression cassette were introduced into plant cells. Using sgRNAs targeting adjacent donor DNA template containing synonymous mutations in sgRNA sites, we achieved precise gene replacements in the endogenous B. napus EPSPS gene, BnaC04EPSPS, resulting in amino acid substitutions at frequencies up to 20%. Rapeseed seedlings harbouring these substitutions were glyphosate-tolerant. Furthermore, modifications in BnaC04EPSPS were precisely transmitted to the next generation. Our genome editing strategy enables highly efficient gene targeting and the induction of glyphosate tolerance in oilseed rape.

Weed Control Using Paddy Straw Mulch in Integration with Herbicides in Autumn Potato in North-West India

Weeds are a major problem in potato production. Two years of trials were conducted to study the efficacy of herbicides and integrated use of mulch with herbicides in controlling weeds and for improving the growth and yield of autumn potato crop at Ludhiana, north-west India, during autumn 2016 and 2017. Each trial had a randomized complete block design with three replicates. There were 11 treatments including weed-free and weedy controls. Uncontrolled weeds caused a yield reduction of 49.7%. Metribuzin at 350 g/ha pre-emergence resulted in 82.4% weed control efficiency at 30 days after planting but this control was reduced to 23.9% at harvest. In contrast, metribuzin at 350 g/ha applied post-emergence controlled broadleaf weeds and grasses very effectively. Clodinafop at 60 g/ha post-emergence resulted in control of grasses only. The post-emergence application of pre-mix clodinafop plus metribuzin at 260 g/ha provided effective weed control and resulted in more tuber yield and economic returns and was significantly better than an application solely of metribuzin or clodinafop. The integrated weed control treatment of paddy straw mulch (PSM) at 6 t/ha with clodinafop plus metribuzin at 195 g/ha post-emergence resulted in the highest tuber yield with weed control efficiency of 95.3% at harvest. The next best one was an integrated treatment of PSM at 6 t/ha with metribuzin at 275 g/ha pre-emergence.

Herbicidas flumioxazin e clethodim na formação de mudas cacaueiras / Flumioxazin and clethodim herbicides in the formation of cacaueir seedlings

One of the most important factors in the formation of cocoa crops is the use of quality seedlings. However, during the formation of seedlings in the nursery, competition for weeds can limit their development. Thus, the objective was to evaluate the efficiency of application of the herbicides Clethodim and Flumioxazin in the control of weeds and their effects on the development of cocoa seedlings under nursery conditions. A completely randomized design was adopted, in a 2x6 factorial scheme with four replications, the first factor being the herbicides clethodim and flumioxazin and the second factor representing the doses of these herbicides, in which, 0, 1, 2, 4, 8, 16 L ha-1 corresponding to 0, 24, 48, 96, 192, 384 g ia ha-1 of the active ingredient Clethodim and 0, 30, 60, 120, 240, 480 g ia ha-1 of Flumioxazin respectively. At 120 days after emergency application of the plants, the effects caused by herbicides on the development of cocoa seedlings and their effectiveness in weed control were evaluated. The post-emergence use of the herbicide clethodim promoted a better development in the cocoa seedlings in relation to the pre-emergence application of the herbicide Flumioxazin. Both herbicides were efficient in controlling weeds, the maximum control being obtained with the dose of 4.61 L. ha-1 of these herbicides, which corresponds to 110.4 g ai ha-1 of the herbicide clethodim and 138 g ia ha -1 of flumioxazin.

Selectivity and efficiency of herbicides in cassava on the floodplain of the Solimões river

Cassava is grown on the floodplains of the Solimões river and guarantees food security and income for farmers. However, negative interference of weeds can result in a significant yield loss in the crop. Therefore, the aim of this study was to evaluate the selectivity of herbicides and efficiency of chemical weed control in the cassava ‘Aipim-manteiga’ cultivar, in the floodplain of the Solimões river, in Iranduba, Amazonas. The experimental design was in randomized blocks with four replications. The herbicides evaluated were clomazone (1080 g ha-1), diuron (1750 and 2500 g ha-1) and oxadiazon (400 and 800 g ha-1), applied alone or with hoeing 90 days after planting (DAP). Two control treatments were included: weeding (hoeing) at 30, 60, 90 and 120 DAP and with no weed control. Clomazone caused mild toxicity in the plants, while with diuron and oxadiazon toxicity was moderate; all three were considered safe for the crop. The plant population of the crop was not affected by the herbicides. Clomazone afforded effective weed control up to 45 DAP only, and weeding was necessary at 90 DAP to eliminate negative interference by the weeds on crop yield. Diuron and oxadiazon were effective in controlling weeds throughout the crop cycle of the cassava. Weed interference during the crop life cicle reduced yield by 83.8%.

Soil solarization improves soil fertility in addition to weed management in sesame under subtropical conditions of Pakistan

Abstract Background: Thermal weed control is a viable, cost-effective, and eco-friendly emerging alternative to highly challenged and unsustainable chemical weed control. Objective: To find out the most suitable pre-sowing soil solarization durations for effective weed control and soil fertility enhancement in sesame crop. Methods: A field study was conducted during the summer season of 2016 and 2017. Different soil solarization treatments were applied, including 0, 3, 6, 9, and 12 weeks before sowing (WBS) of sesame by spreading transparent polythene sheets. Results: The temperatures of solarized soil at 10 cm depth were 8-10 oC more than the control. The soil NPK and organic matter contents were gradually increased with increasing solarization durations. The highest soil nitrogen (0.71%), phosphorus (9.63 ppm), K (166.2 ppm), and organic matter content (1.12%) were observed with the longest soil solarization for 12 WBS. Different solarization durations provided 23 to 64% weed control efficiency and up to a 34% rise in sesame yield. Conclusions: Based on the current findings, soil solarization for 12 WBS by polythene sheets is an effective alternative to the chemical weed control method with additional positive effects on soil fertility and sesame yield.

Effects of Poultry Manure Fertilization and Weed Control Method on Leaf Chlorophyll and Other Indices of Three Maize (Zea mays) Cultivars in Kano Sudan Savanna, Nigeria

The present study was conducted in 2016 and 2017 rainy seasons to determine the responses of poultry manure (PM) on chlorophyll and other indicates in three maize cultivars, a split-split plot design with three replications was used. The experiment consists of SAMMAZ 15, 21, and 35 in the main plot, PM (0, 4, 8 and NPK) in sub-plot and weed control method (S-Metolachlor + Atrazine at 2.0kg a.i. ha-1 fb Nicosulfuron at 100 g a.i. ha-1, S-Metolachlor + Atrazine at 2.0kg a.i. ha-1 fb Bentazone at 2.5kg a.i. ha-1, Metolachlor + Terbuthylazine + Mesotrione at 2.5kg a.i ha-1 fb Nicosulfuron at 100g a.i. ha-1, Metolachlor + Terbuthylazine + Mesotrione at 2.5kg a.i ha-1 fb Bentazone at 2.5kg a.i. ha-1, two hoe weeded at 3, and 6 WAS and Weedy check) in sub-sub plots. Results showed that effective weed control method and PM/NPK significantly increased all indices. The Interaction of variety and poultry manure indicate that SAMMAZ 21 and 35 had the highest value of higher chlorophyll, dry matter and grain yield using NPK or 8 tha-1 PM. Thus, it can be suggested that planting SAMMAZ 21 or 35 with 8 tha-1PM or NPK using Metolachlor + Terbuthylazine + Mesotrione at 2.5 kg a.i ha-1 fb Bentazone at 2.5 kg a.i. ha-1 improve maize production.

A new device for selective mechanical broadleaf weed control in turfgrass

AbstractWeed control in turfgrass systems without herbicides can be challenging. Cost effective and reliable weed control options are needed in turfgrass systems managed organically or pesticide‐free. The objectives of this research were to determine i) the efficacy of selective, mechanical broadleaf weed control and ii) assess Weedbine injury potential in Poa pratensis L. (Kentucky bluegrass). This study was arranged in a randomized completed block design with two replications. The three treatments were: 1) Weedbine 1X wk–1, 2) synthetic herbicide, and 3) mow only control. Synthetic herbicides provided the quickest and most definitive level of weed control. However, the Weedbine used once per week immediately prior to mowing provided significantly higher weed control compared to the mow only control consistently throughout the growing season. Mechanically treated plots exhibited some turfgrass injury following treatments in August and September. However, mechanically treated plots had higher turfgrass quality than herbicide‐treated plots in November due to subsequent weed encroachment in herbicide treated plots later in the growing season. The Weedbine has potential for applying selective, mechanical weed control with minimal injury in Poa pratensis.