Postemergence Herbicide Applications Research Articles

Effects of pre-emergence herbicide on targeted post-emergence herbicide application in plasticulture production

Effects of pre-emergence herbicide on targeted post-emergence herbicide application in plasticulture production

Effect of weed management options and nitrogen scheduling on weed dynamics and yield of wheat (Triticum aestivum) under Central Plain Zone of Uttar Pradesh

A field experiment was conducted during the winter (rabi) seasons of 2014–2015 and 2015–16 at Kanpur, Uttar Pradesh, to study the effect of weed-management options and nitrogen scheduling on weed dynamics and yield of wheat (Triticum aestivum L.). Common infesting weeds which appeared in wheat field were Phalaris minor Retz. and Cynodon dactylon (L.) Pers. among grasses, and Chenopodium album L., Anagallis arvensis L., Melilotus alba Medik. and Convolvulus arvensis L. as broad-leaf weeds. Moreover, among sedges, only 1 species, Cyperus rotundus L. was observed. Among the weed-management options, mesosulfuron-methyl + Iodosulfuron-methyl sodium (400 g/ha) with higher dose of nitrogen (150 kg N/ha) applied in 3 spilt applications [50% as basal + 25% at crown-root initation (CRI) + 25% at flowering] proved significantly superior in minimizing the density (33%) and biomass of weeds (34%) at 60 days after sowing (DAS). The former treatment increased the leaf-area index (LAI) and SPAD values that elevated the production of wheat grain yield. Among time of nitrogen application, 3 splits (50% as basal + 25% at CRI + 25% at flowering) enhanced the nutrient-uptake efficiency (27.4%) and total nutri ent uptake (40.2%) by crop than 3 equal splits at sowing (basal), CRI and flowering. Higher dose of nitrogen (150 kg N/ha) resulted in higher yield (15.7%) and nutrient uptake (13.4%) than its lower dose. Thus, application of ready-mixed post-emergence herbicides, i.e. mesosulfuron + iodosulfuron (400 g/ha) with higher dose of nitrogen (150 kg N/ha) applied 50% as basal and 25% top-dressed at CRI and 25% at flowering was most effective with re spect to weed-suppression, yield and economics of wheat.

Hygienic assessment of occupational risk for workers during pre- and post-emergence herbicide treatments of sunflower crops

Modern agriculture extensively uses pesticide formulations at various stages of crop growth. Sunflower cultivation accounts for 31% of the global production. Assessing the occupational risk associated with pesticide application in sunflower farming is of paramount importance. Improper handling and application of pesticide formulations can have immediate adverse effects on workers, leading to acute poisoning, long-term health consequences, and the potential for chronic illnesses, including neurotoxic effects. The aim of this study was to conduct a hygienic assessment of the professional risk faced by workers during pre- and post-emergence herbicide applications in sunflower cultivation. This assessment was carried out to establish the regulations for their safe usage. Research samples after the application of the herbicides AGAT, GARPUN, KORVUS, and PARUS (patches from overalls, gloves, skin swabs from exposed areas (face-neck, hands), air samples (atmospheric air, working zone and drift zone). The assessment of professional risk was conducted in accordance with the methodological recommendations provided by experts from the L.I. Medved's Research Center of Preventive Toxicology, Food and Chemical Safety, Ministry of Health, Ukraine (State Enterprise). Statistical analysis of the results was carried out using the licensed statistical software packages MedStat v.5.2 (Copyright© 2003-2019) and Microsoft® Excel® for Microsoft 365 MSO (Version 2305, Build 16.0.16501.20074). It has been determined that under real conditions, during pre- and post-emergence herbicide applications in sunflower cultivation using AGAT, GARPUN, KORVUS, PARUS preparations, while adhering to recommended agrotechnical and hygiene safety regulations, the inhalation, dermal, complex, and combined (AGAT and PARUS) risks for applicators are 0.0409±0.0179, 0.0429±0.0193, 0.0838±0.0224, and 0.1557±0.1322 a.u., respectively, and for tractor operators – 0.0818±0.0358, 0.0425±0.0192, 0.1243±0.0356, and 0.2347±0.1567 a.u., respectively. There is no observed increase in hygiene standards in the workplace atmosphere and in the air of the potential drift zone. It has been proven that the professional risk of their use does not exceed permissible limits (<1). It has been determined that during the performance of techno­logical operations, the mentioned risks in applicators and tractor operators did not differ significantly (p>0.05). However, a significant difference was found in the proportion of percutaneous risk (42.7±17.4% in applicators compared to 34.8±17.0% in tractor operators; p=0.034). The regulations for the safe use of the investigated pesticide formulations have been substantiated. Statistical analysis of the obtained results revealed that the values of inhalation, dermal, and combined risks during the application of these pesticides did not significantly differ during the various technological operations (applicators and tractor operators) (p>0.05). The values of the combined comprehensive risk associated with the use of the studied preparations also did not show significant differences (p>0.05). The proportion of dermal risk was significantly higher in applicators compared to this parameter determined in tractor operators (p=0.034).

Response of Jabuticaba [Plinia cauliflora (Mart) Kausel] seedlings to herbicides

Jabuticaba (Plinia sp.) is one of the most important fruit species in the Brazilian flora; it is appreciated for fresh consumption or products produced from its fruits. The establishing of orchards requires the determination of management methods that favor the development and productivity of this species. The objective of this work was to evaluate the response of jabuticaba seedlings to application of herbicides and determine possible phytotoxicity. The experiment was conducted at the Federal Technological University of Paraná, in Dois Vizinhos, PR, Brazil. A randomized block experimental design with four replications was used, with 5 plants per experimental unit. The treatments consisted of applications of pre-emergence herbicides (Dual Gold® and Spider®) and post-emergence herbicides (2,4-D, Ally®, Enlist®, Primatop®, Fusilade®, Imazetapyr, Flex®, Plenum®, and Volcane®). The applied herbicide rates were equivalent to 50% of their commercial recommendation. A spray volume equivalent to 250 L ha-1 was applied, using water as diluent. The following parameters were evaluated 45 days after applications: stem diameter at 1 cm above ground (cm); plant height (cm); numbers of necrotic, chlorotic, shriveled, and healthy leaves; number and length of shoots (cm); survival rate (%); and chlorophyll contents (a, b, and total). The application of the herbicides Ally®, Enlist®, and Flex® resulted in less harmful effects on jabuticaba seedlings. The lowest survival rates were found in plants in the treatments with the herbicides Dual Gold®, Volcane®, and Primatop®.

Johnson Grass (Sorghum halepense) Interference, its Effect on Crops Yield and Soil attributes under Different Cropping Systems and Management Practices

Johnson grass (Sorghum halepense) is one of the most detrimental and toxic weeds among the weed species. Its environment is expanding unceasingly due to deeply expanding of its rhizomes in the soil, self-pollinating reproduction strategy, accelerated growth and poor management which results in production losses of major agronomic crops. Mungbean and sorghum are important crops grown on significant acreage around the world, and a major constraint for their production losses is weeds interference. Thus, field studies were conducted to examine Johnson grass interference, control, and recovery under different management practices and cropping system and its effects on crops production and soil health. Our results indicated that the Johnson grass density was minimized by the application of plastic sheet mulch treatment under wheat-mungbean cropping system. Johnson grass competition had a significant impact on growth and grain yield of both mungbean and sorghum. The crop yield parameters; 100 grain weight and grain yield were lowest in the non-treated treatment (control), while the greatest values of these parameters were recorded in the plastic sheet mulch and post emergence herbicide treatments with wheat-mungbean cropping system. Similarly, soil building attributes; available nitrogen, available phosphorus, available potassium and organic matter content were positively affected by the interaction of plastic sheet mulch + wheat-mungbean cropping system. Besides this, benefit-cost ratio of the research shows that wheat-mungbean cropping system with application of plastic sheet mulch and post emergence herbicide also proved to be economically feasible. Overall, we have concluded that wheat-mungbean and wheat-sorghum are most resilient cropping system with the implementation of plastic sheet mulch and Post Emergence Herbicide to suppress the spread of Johnson grass under changing climatic scenarios.

Investigation of management practices to optimize cereal rye cover crop-based weed mitigation in Canadian sweet corn production

Abstract Fall-sown cereal rye has gained popularity as a cover crop in vegetable production due to its weed-suppressive capabilities. However, previous research has shown that replacing preemergence and/or postemergence herbicide applications with roller-crimped rye has variable success at controlling weeds and maintaining vegetable cash crop yields. The objective of this research was to determine whether roller-crimped rye can provide season-long weed control and maintain sweet corn yield. Two rye cultivars (early vs. standard maturity) were compared at three seeding rates (150, 300, and 600 seeds m−2) for their effect on weed control and sweet corn yield. The trial was conducted at three locations: Harrow, ON, and St. Jean-sur-Richelieu, QC, from 2019 to 2021; and Agassiz, BC, in 2019 and 2021. Results suggest that although the early-maturing cultivar allowed for earlier roller crimping in some locations, it was inferior at weed control and resulted in lower sweet corn yield than local standard cultivars. The average rye biomass was lower than the current literature recommendations, and the resulting level of weed control was not high enough to prevent sweet corn yield loss in cover crop treatments. Weed control provided by roller-crimped rye peaked between crimping and 8 wk after crimping and was highest in the standard cultivars sown at 300 and 600 seeds m−2. Preliminary testing of supplemental postemergence weed control showed evidence for sweet corn yields comparable to the weed-free no-cover crop check. However, more research is needed. Overall, with the cultivars and seeding rates tested, roller-crimped rye is not a suitable stand-alone weed control option in sweet corn production. Given the benefits of cover crops, further research should evaluate its potential as a component of an integrated weed management program.

Spray interval, application order, and plant height influences control of dicamba-resistant Palmer amaranth

Abstract Palmer amaranth, which is resistant to glyphosate and protoporphyrinogen oxidase inhibitors, remains a threat to cotton and soybean production in Tennessee. This is partly due to the recent evolution of dicamba-resistant Palmer amaranth in western Tennessee, which further complicates weed management. Experiments were conducted in 2021 and 2022 to determine the best timing between sequential applications and the order in which 2,4-D or dicamba should be used with glufosinate to control resistant Palmer amaranth. Palmer amaranth control increased when the interval between postemergence herbicide applications decreased from 21 to 7 d. At the 7-d interval in a dicamba-based system, the order of herbicides did not affect Palmer amaranth control. However, in a 2,4-D-based system, the greatest control was achieved when 2,4-D was applied first, followed by either 2,4-D or glufosinate. While weed height at the time of application had a significant effect on Palmer amaranth control with auxin herbicides, control was still unacceptable in the field at the labeled rates of dicamba or 2,4-D when applied to weeds that were <10 cm tall (48% and 53%, respectively). Neither dicamba nor 2,4-D provided acceptable control of the Palmer amaranth populations evaluated in this study. Sequential applications separated by 7 d provided better weed control than those separated by 21 d. Given that the better 7-d sequential treatments provided less than 90% control and resulted in more than 64,000 surviving Palmer amaranth plants per hectare suggests that relying solely on these herbicides for Palmer amaranth control is not a sustainable weed management strategy.

Critical Period of Weed Control in Maize as Influenced by Soil Tillage Practices and Glyphosate Application

Increasing evidence on environmental and economic benefits has raised farmers’ interest in adopting alternative, less intensive soil management practices. To evaluate the influence of weed-competitive ability in response to a different tillage regime, a field study was conducted in maize under humid Central European climatic conditions in Slovenia. This study was established as a split-plot arrangement with three tillage practices (TPs) as the main plot: conventional (CN), conservation (CS), and no tillage (NT); this was combined with glyphosate application and the weed removal timing as the subplot. The weed removal timings were at the V3, V6, V9, V15, and R1 maize stages, with weed-free and weed season-long monitoring. The beginning and the end of the critical period of weed control (CPWC), based on a 5% maize yield loss rate, were determined by fitting the four-parameter log-logistic equations to the relative maize dry grain yield. The weed dry biomass from maize germination until the R1 growth stage in the NT TP was consistently lower than that in the CN and CS TP. Moreover, the NT TP resulted in a shorter CPWC (39 days after emergence (DAE)) compared to the CN (57 DAE) and CS (58 DAE). The results of CTWR (critical timing of weed removal) showed that less intensive tillage operations in the CS resulted in an earlier need for weed control (V2 and 23 DAE) compared to the CN (V3 and 39 DAE) and NT (V3 and 40 DAE). Our study suggests that the intensive tillage operations performed in the CN TP and the pre-sowing use of non-selective burndown herbicide in the NT delay the CTWR by more than 2 weeks, thus reducing the need for early post-emergence herbicide application in maize.

Weed management strategies in elephant foot yam (<i>Amorphophallus paeoniifolius</i>) under different agro environments in India

In elephant foot yam [Amorphophallus paeoniifolius (Dennst.) Nicolson], weeds are the major constraints cause yield reduction up to 100% due to its very slow initial sprouting, establishment and plant growth. Information on proper weed management in elephant foot yam in India is limited as its commercial cultivation started very recently. For arriving at suitable and better weed control, field experiments were conducted for 3 growing seasons (2019 to 2021) at ICAR-Central Tuber Crops Research Institute, Thiruvananthapuram, Kerala with 8 treatments in 6 different agro-climatic zones of India. The treatments included a combination of pre emergence (PE) and post emergence (POE) herbicides, PE followed by hand weeding (HW), intercropping followed by POE, HW with POE, POE alone, and weed control ground cover cloth mulch (WCGCC), three HW, and a weedy check were included for comparison. Weed flora was dominated by broad-leaf weeds, Digera arvensis (L.), Commelina benghalensis (L.); grasses, Pennisetum pedicellatum Trin., Cynodon dactylon (L.) pers.; and the sedge, Cyperus rotundus (L.), in most of the locations. Pooled analysis of data collected over different locations indicated that the lower mean weed biomass (21.24 g/m) and higher mean corm yield (35.13 t/ha), higher mean net income (`0.326 million/ha) were recorded with weed control ground cover mulch and higher mean B:C ratio (2.39) by application of post emergence herbicide at 30, 60 and 90 days after planting (DAP).

Palmer Amaranth (Amaranthus palmeri) Control in Dicamba-Tolerant Cotton (Gossypium hirsutum) when Applied with Various Dicamba + Insecticide Tank-Mixtures

Postemergence herbicide application timings for Palmer amaranth (Amaranthus palmeri) often coincide with foliar insecticide applications in cotton (Gossypium hirsutum). Combining multiple pesticides into a single application increases efficiency while reducing overall application cost. Multiple foliar insecticides are now labeled for dicamba tank-mixes. However, there is limited literature with respect to efficacy of dicamba on Palmer amaranth control when applied with insecticides. Field experiments were conducted from 2018 to 2020 to evaluate the effect of carrier volume and insecticide on the efficacy of dicamba (XtendiMaxTM with VaporGripTM) to control Palmer amaranth in XtendFlex™ cotton production systems. Dicamba was tank-mixed with acephate and dimethoate to four-leaf cotton and with thiamethoxam and sulfoxaflor just prior to bloom. Applications were made at carrier volumes of 140 and 280 L ha-1 and with a single spray droplet size of 800 µm. Palmer amaranth control 7 d after treatment was negatively impacted when applications included dimethoate; however, no corresponding response in seedcotton yield was observed relative to dicamba applied alone. However, when pooled over carrier volume, applications containing dicamba + acephate resulted in higher seedcotton yield than applications of dicamba + dimethoate. Additionally, pre-bloom applications of dicamba + thiamethoxam or sulfoxaflor increased Palmer amaranth efficacy relative to dicamba applied alone. Although certain insecticides are known to increase herbicidal crop response, the impact of insecticides on herbicide efficacy to control specific weed species is largely unknown. Therefore, we conclude that multiple dicamba + acephate, thiamethoxam, or sulfoxaflor tank-mixtures provide similar control of Palmer amaranth compared to dicamba alone.

A systematic review of chemical weed management in peanut (Arachis hypogaea) in the United States: challenges and opportunities

AbstractHerbicides are the primary tool for controlling weeds in peanut (Arachis hypogaea L.) and are crucial to sustainable peanut production in the United States. The literature on chemical weed management in peanut in the past 53 yr (1970 to 2022) in the United States was systematically reviewed to highlight the strengths and weaknesses of different herbicides and identify current research gaps in chemical weed management. Residual weed control in peanut is achieved mainly with dimethenamid-P, ethalfluralin, pendimethalin, and S-metolachlor. More recently, the use of the protoporphyrinogen oxidase inhibitor flumioxazin and acetolactate synthase inhibitors, such as diclosulam, for residual weed control in peanut has increased considerably. Postemergence broadleaf weed control in peanut is achieved mainly with acifluorfen, bentazon, diclosulam, imazapic, lactofen, paraquat, and 2,4-DB, while the graminicides clethodim and sethoxydim are the major postemergence grass weed control herbicides in peanut. Although several herbicides are available for weed control in peanut, no single herbicide can provide season-long weed control due to limited application timing, lack of extended residual activity, variability in weed control spectrum, and rotational restrictions. Therefore, effective weed management in peanut often requires herbicide mixtures and/or sequential application of preplant-incorporated, preemergence, and/or postemergence herbicides. However, the available literature showed a substantive range in herbicide efficacy due to variations in environmental conditions and flushes of weed germination across years and locations. Despite the relatively high efficacy of herbicides, the selection of herbicide-resistant weeds is another area of increasing concern. Future research should focus on developing new strategies for preventing or delaying the development of resistance and improving herbicide efficacy within the context of climate change and emerging constraints such as water shortages, rising temperatures, and increasing CO2 concentration.

Evaluation of the effect of nicosulfuron and bentazone herbicides on growth and yield performance of two maize varieties in Mubi, Nigeria

Abstract. Tizhe TD, Alonge SO, Adekpe DI, Ioortsuun DN. 2023. Evaluation of the effect of nicosulfuron and bentazone herbicides on growth and yield performance of two maize varieties in Mubi, Nigeria. Asian J Agric 7: 122-130. This study aimed to determine the effect of nicosulfuron and bentazone herbicides on the growth and yield performance of maize (Zea mays L.) varieties SAMMAZ 17 and SAMMAZ 37 in Mubi, Nigeria. The study was carried out between 2019 and 2020 wet seasons. Nicosulfuron and bentazone herbicides at 50, 100, 150, and 200 g/ha and 0.5, 1.0, 1.5, and 2.0 kg a.i/ha concentrations, respectively, along with hoe weeded and weedy check controls were applied in the field of the two maize varieties at 3, 5 and 7 Weeks after Sowing (WAS). The maize growth parameters were determined two weeks after treatment at three different times, while the yield parameters were determined using standard procedures. The results showed that nicosulfuron and bentazone had no significant effect on the Crop Growth Rate (CGR), Net Assimilation Rate (NAR), days to 50% silking (except Relative Growth Rate and days to 50% tasselling), and plant height, leaf area index and total biomass of the two maize varieties, when sampled at 2 and 4 (except at 6 weeks) weeks sampling after herbicides application at 3, 5 and 7 WAS. The application at 3 WAS resulted in lower values for virtually all the growth parameters than that at 5 and 7 WAS. The two herbicides, however, significantly affected most of the maize yield parameters. The maize plants on plots treated at 3 WAS had the highest values for all the yield parameters (except kernel depth) than those treated at other periods. The study concluded that the post-emergence application of nicosulfuron and bentazone herbicides had no significant influence on the growth parameters of SAMMAZ 17 and SAMMAZ 37; however, there was a significant effect on the yield parameters.

Steam application with paraquat to control goat weed (Scoparia dulcis) in citrus orchards

Reducing herbicide use in horticultural crop production can ameliorate adverse environmental effects but may also impact weed control effectiveness, especially as it pertains to difficult-to-control weeds. This challenge can be addressed by integrating a non-chemical strategy such as steam application with herbicide application. In this study, steam, as a non-chemical approach, was combined with post-emergence herbicide (paraquat) application for goatweed (Scoparia dulcis) management in citrus orchards. Two field trials based on randomized complete block design were conducted in citrus orchards in Immokalee, FL, in 2018 and 2021. Steam was applied to goatweed at a flow rate of 53 L ha−1 for 5–6 s. Twenty-four hours after steam application, low and high paraquat rates (0.3366 and 1.010 kg ai ha−1) were applied. In addition, the same rates of paraquat were applied without steam for comparison. Untreated checks (UTC) of no herbicide or steam applications were also included in the experiment as a control. Based on visual injury ratings, a combination of steam + low dosage of paraquat was as effective as the high dosage of paraquat alone and steam + high dosage of paraquat at 1, 8, and 16 days after treatment application (DAT) in 2018 trial and 1, 8, 16 and 22 DAT in 2021 trial.However, based on one site-year of biomass data, the percentage of dead weed biomass out of total biomass was statistically similar among all the treatments. Results from this study demonstrate that combining a low rate of paraquat applied in tandem with the steam application has the potential to provide effective goatweed control in citrus orchards.

A field study on the combined use of pre-emergence herbicide and Clearfield® technology for ryegrass management in wheat crops

Weed interference in wheat crops are known to cause productivity losses. The objective of this work was to evaluate pre-emergence herbicide application efficiency combined with Clearfield® technology (CL) in ryegrass (Lolium multiflorum) management in wheat crops. A field experiment was conducted from July 2020 to December 2021 using randomized block design in a 2×5 factorial arrangement with four replications. Treatments consisted of combinations of pre-emergence herbicide application - without and with pendimethalin at 1365 g a.i. ha-1 (in 2020 crop season) or without and with pyroxasulfone at 125 g a.i. ha-1 (in 2021 crop season) and post-emergence herbicide application - without application; imazamox at 49, 70, and 91 g a.i. ha-1, or pyroxsulam at 18 g a.i. ha-1. Wheat cultivars used were TBIO Capricho CL® and TBIO Ello CL®. The following characteristics were evaluated: phytotoxicity, ryegrass control, plant height, number of spikes m-2, mean spike weight, 100-grain weight, and grain yield. Treatments phytotoxicity did not exceed 5%, being visible only at 7 DAA, from 14 DAA no injury was observed. The combined application of pre-emergence herbicides pendimethalin or pyroxasulfone with post-emergence herbicides imazamox or pyroxsulam provided superior control of ryegrass than the isolated applications. This management resulted in ryegrass control ranging from 88.8% to 100% in 2020 and from 82.3% to 100% in 2021. In general, grain yield was also higher in treatments with combined pre- and post-emergence applications. The pre-emergence herbicide application in combination with CL technology was effective in managing ryegrass, preventing weed interference, and ensuring the productive potential of wheat crops

Comparative studies of knapsack, boom, and drone sprayers for weed management in soybean (Glycine max L.)

The study titled, "Comparative Evaluation of Knapsack, Boom, and Drone Sprayers for Weed Management in Soybean (Glycine max L.)" was carried out during the Kharif season 2021-22 at an experimental farm affiliated with the Department of Agronomy, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani. The primary objective was to evaluate the comparative efficacy of various sprayers in controlling weeds in soybeans and their work efficiency. The Randomized Block Design (RBD) included ten treatments of pre-emergence (PE) and post-emergence (POE) herbicides applied by knapsack, boom, and drone sprayers. Pendimethalin 30% EC @ 750 g a.i ha−1 was used for pre-emergence herbicide application, and Imazamox 35% EC + Imazethapyr 35% WG @ 70 g a.i ha−1 were used for post-emergence. These treatments were tested on soybean Monocot and Dicot weed count, weed dry weight, weed index, and weed control efficiency. The sprayers were compared for time, water, labor, herbicide, and overall work efficiency. A knapsack sprayer showed the best results for pre- and post-emergence herbicide application, with the lowest weed count, dry weight, control efficiency, and weed index. Boom and drone sprayers followed in effectiveness. Herbicide application was faster with the drone sprayer than with hand weeding, cultural practices, boom sprayer, and knapsack sprayer. Compared to knapsack and boom sprayers, the drone sprayer used less water and labour. Drone sprayers work most efficiently, followed by boom and knapsack sprayers. This study focuses on the prevalence of herbicides and their impact on non-target ecosystems. It aims to develop mitigation strategies by optimizing spraying efficiency and reducing herbicide usage during pre and post emergence. The dissemination of efficient weed management practices that reduce environmental impacts and increase the efficiency of soybean cultivation is consistent with Sustainable Development Goal 15: life on land.

Above Ground Emergence and Floristic Composition of Weeds in Relation to Tillage and Weed Management Practices in Maize and Cowpea

Background: Weeds are one of the most important elements influencing crop productivity. Tillage practices have a significant effect on the weed seed bank and the appearance of weeds, both of which have a direct impact on farm productivity. Different tillage strategies based on ploughing depth, as well as weed control practices, change the dynamics of weed seeds in the soil. This research will aid in the development of integrated weed control methods by investigating the interaction between tillage and weed management practices. Methods: Field trials were carried out in two seasons, Summer and Kharif 2022, using a split-plot design with three tillage methods and four weed management practices. The treatments were replicated three times. Result: Among the different tillage treatments Mouldboard plough fb Cultivator fb Rotovator recorded the lowest weed density. With respect to weed management methods, pre- and post-emergence herbicide application and hand weeding at 20 and 40 DAS recorded the lower weed density. Interaction effects of tillage and weed management practices resulted in lower weed density in Mouldboard plough fb Cultivator fb Rotovator with herbicide application and Mouldboard plough fb Cultivator fb Rotovator with hand weeding. Highest weed density was recorded under Cultivator fb Rotovator in unweeded control. With respect to relative density, among the broad-leaved weeds (BLW) Trianthema portulacastrum and Dactyloctenium aegyptium in grasses dominated among the weed species in 30 and 60 DAS respectively. From the present study it was concluded that the Mouldboard plough fb Cultivator fb Rotovator with hand weeding twice or herbicide application reduces the weed emergence from the soil weed seed bank.

Herbicide response and germination behavior of two goosegrass (Eleusine indica) populations in the Australian environment

AbstractGoosegrass [Eleusine indica (L.) Gaertn.] is one of the most problematic grassy weeds in the world. It is considered to be an important weed in summer fallows and crops grown in the eastern region of Australia. To examine the seed germination ecology of two populations (Gatton and Ingham) of E. indica and their response to postemergence herbicides in Australian conditions, experiments were carried out in the laboratory and screenhouse. Seedling survival, spike production, and plant biomass of both E. indica populations declined markedly with the application of postemergence herbicides such as butroxydim, clethodim, glufosinate, haloxyfop, and propaquizafop, whereas the application of paraquat failed to control the Ingham population. A dose–response study verified the presence of paraquat resistance in the Ingham population. In this regard, it was observed that the paraquat doses required to achieve a 50% reduction in survival and plant biomass were 27 and 21 times greater in the Ingham population compared to the Gatton population, respectively. Higher alternating temperatures (35/25 and 30/20 C) resulted in greater germination of both populations than lower alternating temperatures (20/10 and 25/15 C). At 20/10 C, the Ingham population failed to germinate; however, about 15% germination in the Gatton population was observed. At the lowest alternate temperature range (15/5 C), neither population germinated. The germination of both populations of E. indica was severely reduced under completely dark conditions compared with the alternating light/dark period. Germination was more tolerant of salt and water stress in the Ingham population compared with the Gatton population. Eleusine indica seedling emergence was comparable among populations, and the greatest emergence (83%) was observed for seeds buried at a depth of 2 cm but then declined dramatically, and no seedlings emerged from an 8-cm burial depth. The information acquired from this study could be used in developing effective management strategies for E. indica.

Effect of tillage and weed control practices on weed density, cassava growth and yield at Mkuranga district, Tanzania

Poor and improper weeding in cassava production has been reported to cause cassava yield losses ranging from 40% to 90%. A study was carried out in 2019/2020 planting season at Kiimbwanindi village, Mkuranga, Tanzania to identify common weeds available in the selected cassava field and then the effect of different integrated weed control options was studied. Till only and till + Ridge, pre-emergence herbicides (Primagram Gold a.i 290 g/L S-metolachlor + 370 g/L atrazine and Oxfen a.i Oxyfluorfen 24% EC), post emergence herbicides (Force up a.i 480 g/L of Glyphosate-Isopropylamine salt) and back pack weeder with modified tines were tested on Cassava variety Kiroba in a factorial experiment arranged in a randomized complete block design (RCBD) replicated three times. Data on weed species, weed density, cassava height, girth and fresh root yield and soil were collected. By using Thomas methodology, perennial weeds Cyperus rotundus, Reissantia sp, Mucuna pruriens and Commelina benghalensis found to be the mostly and abundantly occurred weed species. The combination of tillage practices and pre-emergence herbicides application increased number of days’ weeds took to reemerge. The integrated weed control options significantly affected cassava fresh root weight and biomass, p = 0.019 and p = 0.026, respectively. The correlation analysis showed a non-significant positive relationship between cassava stem height and cassava fresh root weight (r = 0.389, p > 0.05), and cassava stem girth and cassava fresh root weight (r = 0.055, p > 0.05). The study concluded that, the combination of till + ridges, application of pre-emergence herbicide (S-metolachlor + atrazine) and post emergence herbicides (glyphosate) can effectively control weeds and provided favorable environment for cassava growth and root formation as compared to other treatment options.

Impact of cereal rye cover crop on the fate of preemergence herbicides flumioxazin and pyroxasulfone and control of Amaranthus spp. in soybean

AbstractPreemergence herbicides associated with cereal rye (Secale cereale L.) cover crop (hereafter “cereal rye”) can be an effective waterhemp [Amaranthus tuberculatus (Moq.) Sauer.] and Palmer amaranth (Amaranthus palmeri S. Watson) management strategy in soybean [Glycine max (L.) Merr.] production. Delaying cereal rye termination until soybean planting (planting green) optimizes biomass production and weed suppression but might further impact the fate of preemergence herbicides. Limited research is available on the fate of preemergence herbicides applied over living cereal rye in the planting green system. Field experiments were conducted in Illinois, Kansas, Pennsylvania, and Wisconsin to evaluate the fate of flumioxazin and pyroxasulfone and Amaranthus spp. residual control under different cover crop management practices in soybean in 2021 and 2022 (8 site-years). A flumioxazin + pyroxasulfone herbicide premix was applied preemergence at soybean planting under no-till without cereal rye, cereal rye early terminated before soybean planting, and cereal rye terminated at soybean planting. Flumioxazin and pyroxasulfone concentrations in the soil were quantified at 0, 7, and 21 d after treatment (DAT), and Amaranthus spp. density was determined at postemergence herbicide application. The presence of cereal rye biomass intercepted flumioxazin and pyroxasulfone at preemergence application and reduced concentration in the soil when compared with no-till, mainly at 0 DAT. Main differences in herbicide concentration were observed between no-till and cereal rye treatments rather than cereal rye termination times. Despite reducing herbicide concentration in the soil, the presence of the cereal rye biomass did not affect early-season residual Amaranthus spp. control. The adoption of effective preemergence herbicides associated with a properly managed cereal rye cover crop is an effective option for integrated Amaranthus spp. management programs in soybean production systems.

Determination of quizalofop-p-ethyl in onion: residual dissipation pattern, weed control efficiency, and food safety assessment under field conditions.

Monitoring pesticide residue levels becomes crucial to maintain quality and guarantee food safety as the consumption of onion green leaves and immature and mature bulbs (either raw or processed) rises. A field experiment was conducted for two consecutive seasons with quizalofop-p-ethyl (5% EC) at 50 and 100 g a.i. ha-1 to evaluate weed control efficiency and to determine terminal residues. Post-emergence application of fop herbicide at 100 g a.i. ha-1 kept the weed density and dry weight reasonably at a lower level and enhanced the productivity of onion with higher economic returns. A rapid, sensitive, and analytical method was developed using high-performance liquid chromatography (HPLC) with excellent linearity (r2 > 0.99). The limit of quantification for quizalofop-p-ethyl was established at 0.04 mg kg-1 with signal to noise (S/N) ratio ≥ 10. The method was successfully applied and initial quantified residues were in the range of 2.5-4.4 mg kg-1 irrespective of seasons and doses. Finally, the presence of targeted herbicide residues in harvested samples was confirmed by liquid chromatography tandem mass spectrometry (LC-MS/MS) under optimized operating conditions. Dietary risk assessment assured harvested onions were safe for consumption at the recommended dose. It also can be concluded that quizalofop ethyl did not adversely influence soil micro-organisms at standard rates of application.