Early Post-emergence Herbicide Research Articles

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.

Effects of Penoxsulam on Photosynthetic Characteristics and Safety Evaluation of Foxtail Millet

Foxtail millet planting has a long history and profound role in agricultural civilization. However, weeds have become one of the obstacles restricting the development of the foxtail millet industry. Penoxsulam, as an early post-emergence herbicide for controlling gramineous weeds in paddy fields, is effective for some broadleaf weeds. In this study, six different doses (CK, 0.5X, 1X, 2X, 3X, 4X) of penoxsulam were sprayed at the 3–5 leaf stage of the conventional variety Jingu 21 to study its effect on the growth and development of foxtail millet, in order to screen out the appropriate spraying concentration. The main results are as follows: Within 15 days after spraying penoxsulam, the plant height and leaf area of foxtail millet decreased with the increase in spraying dose, and gradually recovered 15–25 days after spraying, but there were still significant differences compared with CK. The photosynthetic pigment content, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), the maximum photochemical efficiency (Fv/Fm), photosynthetic system II actual photochemical efficiency (Y(II)), and photochemical quenching coefficient (qP) of foxtail millet decreased with an increase in the penoxsulam spraying dose, while the intercellular CO2 concentration (Ci) and non-photochemical quenching coefficient (NPQ) showed an upward trend. There was almost no significant difference in each index between the spraying dose of 0.5X and 1X and CK, but the photosynthesis of foxtail millet leaves was still significantly inhibited under a spraying dose of 3X and 4X. Penoxsulam had certain growth-inhibiting effects on Echinochloa crus-galli (L.) Beauv. (E. crus-galli), Digitaria sanguinalis (L.) Scop. (D. sanguinalis), Chenopodium album L. (C. album), and Amaranthus retroflexus L. (A. retroflexus) which increased as the spraying dosage increased. Our study found that spraying dose groups of 0.5X and 1X penoxsulam were safe for foxtail millet growth and could be used to control gramineous weeds in fields. Other spraying doses are not recommended in the field due to their serious phytotoxicity to foxtail millet, which provides a new measure for weed control in foxtail millet fields.

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.

Prickly Sida (Sida spinosa L.) and Cotton Response to Pre- and Early Post-Emergence Herbicides

Prickly sida is a troublesome annual weed native to the USA. It was introduced in Greece over two decades ago and has since been infesting cotton crops, where it proved difficult to control. A two-year field study (2021–2022) was conducted in a cotton field (Karditsa, central Greece) heavily infested with prickly sida to evaluate the efficacy of nine treatments against this weed, using pre-emergence (PRE) and early post-emergence (EPOST) herbicides applied at the field rate. At 8 weeks after treatment, prickly sida control was over 90% with pyrithiobac PRE (68.9 g ai ha−1) alone or in mixture with s-metolachlor (960 g ai ha−1) or with isoxaben (150 g ai ha−1) and with the application of pyrithiobac + s-metolachlor PRE (34.5 + 960 g ai ha−1) followed by pyrithiobac EPOST (34.5 g ai ha−1). Flurochloridone + fluometuron PRE (375 + 2000 g ai ha−1), flumioxazin + s-metolachlor PRE (50 + 960 g ai ha−1), or pendimethalin + terbuthylazine PRE (1500 + 750 g ai ha−1) controlled prickly sida by 89–93% in 2021 and 82–90% in 2022. Pyrithiobac EPOST alone or in mixture with trifloxysulfuron did not adequately control prickly sida. Yield was significantly lower in the weedy check and EPOST compared with the PRE treatments. None of the herbicides caused any visual injury to the crop or any reduction in cotton density. Our results can help in the successful management of prickly sida in non-transgenic cotton to maximize cotton yield and quality.

Drone-based herbicide application for energy saving, higher weed control and economics in direct-seeded rice (Oryza sativa)

A field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore during kharif (rainy) and rabi (winter) seasons of 2022 and 2023 to evaluate the efficiency, energy and economics of drone-based herbicide application in direct-seeded rice (Oryza sativa L.). The study was carried out with application of pre-emergence, early post-emergence and post-emergence herbicides using drone and knapsack sprayer to assess the weed control efficiency. Treatments included pretilachlor followed by (fb) application of post-emergence herbicides, such as bispyribacsodium (Na), fenoxyprop ethyl + carfentrazone ethyl and early post-emergence herbicides, such as bispyribac-Na, fenoxyprop ethyl + carfentrazone ethyl, bispyribac-Na fb post-emergence of fenoxyprop ethyl + carfentrazone ethyl, weed-free check and unweeded check. Application of pretilachlor fb bispyribac-Na using knapsack sprayer reduced weed density from 83 to 87% and weed dry weight from 81 to 83% over unweeded plot. Moreover, it was found on par with drone application of same herbicides in both seasons. Pretilachlor fb bispyribac-Na application through knapsack sprayer and drone produced higher grain yield and it was comparable with weed-free plot. Higher net return, benefit: cost ratio (2.27 and 2.09), energy-use efficiency (10.86 and 9.55 MJ) and energy productivity (0.81 and 0.71 kg/MJ) were noticed with drone application of pretilachlor fb bispyribac-Na in both the seasons. From the experiment, drone application of pretilachlor fb bispyribac-Na is found as an effective strategy to manage weeds in direct-seeded rice and more advantageous in terms of energy-use and profitability.

Effect of different weed management practices on production of spring maize in Dang, Nepal

The study was carried out at Lamahi-8, Satbariya, Dang to evaluate the effect of different weed management practices on the production of spring maize. The experiment was carried out in a Randomized Complete Block Design using three replications and seven treatments. Rampur hybrid 10 variety and early post emergence (EPoE) herbicide were used in the experiment. The treatment consisted of single as well as combined weed management methods as T1: Broadcasting-One hand weeding, T2: Broadcasting-Herbicide, T3: Line sown- One hand weeding, T4: Line sown-Herbicide + one hand weeding, T5: Line sown- Mini tiller weeder, T6: Line sown- herbicide + mini tiller and T7: Line sown- One hand weeding + mini tiller. The experiment result showed that the combined application of early post emergence herbicide and mini tiller resulted the highest grain yield (8.62 Mt/ha) with minimum total weed density at 60 DAS (41.33/m2) and at harvest (68/m2) thus resulting minimum weed dry weight at 60 DAS (5.45 g/m2) and at harvest (10.64 g/m2). Sixteen different weed species belonging to 9 different families were identified in the experimental field. The highest benefit: cost (3.37) was obtained in the treatment Line sown-Herbicide + mini tiller weeder which was significantly higher compared to other treatments. Among the treatments applied, one with the application of herbicide in combination with mini tiller weeder was found to be the most effective one that resulted in the minimum weed density and minimum dry weight, higher grain and biological yield with the highest benefit cost ratio thus proving to be the most economical one. At the same time, application of mini tiller weeder as a single method was found to be the next better alternative for weed control in spring maize that could benefit the farmers in comparison to other single weed management practices.

Weed management with Triafamone herbicide in transplanted rice ecosystem

Field experiments were conducted during Rabi 2018-19 (September to January) and Kharif 2019 (May to September). Medium duration rice cv. CO(R) 51 was used as a test variety at Tamil Nadu Agricultural University, Coimbatore, India to study the effect of Triafamone on broad spectrum weed control in transplanted rice. Triafamone was applied at two times. First set of treatments (30, 40,50 and 100 g/ha) applied two to three leaf stage of weeds and second set treatments imposed (30, 40,50 and 100 g/ha) at three days after transplanting of the rice crop. These treatments were compared with Pyrazosulfuron ethy 10% WP @ 15 g/ha, Pretilachlor 5% EC @ 750 g/ha, hand weeding @ 20 and 40 days after transplanting and unweeded control. The major grasses were Echinochloa crus-galli (L.) and E. colonum (L.) while the sedge weed included Cyperus nutans (L.). Among the broad leaved weeds Eclipta alba (L.) and Bergia ammanioides were the dominant species. In both the seasons of the study, lesser population of grass was recorded with the pre and early post emergence application of triafamone herbicide 40 g a.i. ha-1 (1.41 and 1.41 per m-2 at 28 and 42 DAA for both the seasons respectively) and it was closely followed by application of triafamone herbicide 50 g a.i. ha-1 and application of PE Pretilachlor at 0.75 kg a.i. ha-1 and EPOE Pyrazosulfuron ethyl at 15 g a.i. ha-1. The same trend was observed for broad leaved weeds and their weed dry weights. Application of triafamone herbicide at 40 g a.i. ha-1 as pre emergence and early post emergence application recorded highest weed control efficiency of 100, 97.7 and 99.6 % and 97.8% at 42 DAA during both years of experimentation and also resulted in higher grain yield (8052 and 8182 kg ha-1 during rabi 2018-19 and 9018, 9175 kg ha-1 during Kharif 2019). Further, it is noticed that, there was no residual toxicity of herbicide to the succeeding crops. Hence, application of Triafamone 40 g a.i. ha-1 either pre or early post emergence herbicide has higher productivity and no residues in transplanted rice ecosystem.
 Key words: Triafamone, efficacy, weeds and transplanted rice ecosystem

Weed Dynamics, Productivity and Profitability of Transplanted Aman Rice as Influenced by Integrated Nutrient Management and Weeding Regime

The excessive and improper application of fertilizers is the key factor contributing to nutrient losses to the environment and a decrease in the fertility of the soil. Also, using the wrong herbicide, applying higher than the recommended rate, or improper timing of application can cause crop damage. These factors adversely affect soil productivity and environmental stability. There is thus a need to expand an effective and inexpensive integrated nutrient management and weed control practice for acquiring better yields and profit from rice. The aim of the study was to find out the effect of six integrated nutrient management i.e., BRRI Recommended Dose (RD) of chemical fertilizer, 50% RD + 5 t of cowdung ha-1, 50% RD + 10 t of cowdung ha-1, 50% RD + 2.5 t of poultry manure ha-1, 50% RD + 5 t of poultry manure ha-1, USG 1.8 g 4 hills-1 + TSP, MoP, Gypsum and ZnSO4 @RD along with four weeding regimes i.e., control (no weeding), pre-emergence herbicide followed by one hand weeding at 30 DAT, early post-emergence herbicide followed by one hand weeding at 30 DAT, pre-emergence herbicide followed by early post-emergence herbicide on weed control, rice productiveness, and profitability. Our findings suggest that the application of 50% of the RD of chemical fertilizer + 5 t of poultry manure ha-1 with the application of pre-emergence herbicide followed by early post-emergence herbicide enhances weed suppression and provides higher rice productivity and profitability and can be practiced for the maximization of the yield and net return of transplanted aman rice.

A rapid quantification method for simultaneous determination of pendimethalin and metribuzin contents in suspoemulsion formulation

Pendimethalin and metribuzin are combined to a suspoemulsion (SE) formulation that is treated as a pre-emergence and early post emergence herbicide. A simple reverse phase high performance liquid chromatography (RP-HPLC) method has been validated and applied for the simultaneous analysis of metribuzin and pendimethalin contents in suspoemulsion formulation. The mobile phase for the method was acetonitrile: water (65:35v/v) at a flow rate of 1.0 mL/min, and quantification was accomplished at 237 nm. Hypersil ODS column was used for the method's development and validation. Metribuzin's and pendimethalin's RTs were found to be 3.6 and 11.9 min, respectively. The limit of detection was 0.03 mg/l and 0.04 mg/l for Metribuzin and Pendimethalin respectively. The limit of quantification values was 0.09 mg/l for metribuzin and pendimethalin. The linearity of proposed method was investigated in the range of 2.51 to 100.54 mg/l (r2 = 99997) and 0.25 to 9.80 mg/l (r2 = 99997) for Pendimethalin and Metribuzin respectively. The percentage recovery found to be in range from 99.8 to 100.1 % and 99.8 to 100.3 for Pendimethalin and Metribuzin respectively. The percentage RSD values for intraday precision study and inter-day precision study were < 2.22 and < 1.57 for Metribuzin and Pendimethalin respectively as per modified Horwitz equation as requirements by SANCO. The method's performance was validated in terms of selectivity, specificity, precision, linearity, accuracy, LOD, LOQ, and robustness, according to SANCO guidelines. In this study, for the first time, an easy and speedy reverse phase high performance liquid chromatographyapproach for the simultaneous analysis of pendimethalin and metribuzin in SE formulation is presented.

Effects of Herbicidal Weed Control Practices on Yield Performance of T. Aman Rice Varieties in Bangladesh

Using a weed control scheme could assist in reducing potential production losses caused by weeds in paddy fields. Due to certain undesirable adverse effects, there is currently no realistic alternative to chemical weed suppression approaches in rice. The present research aimed to assess how various herbicide-based weed control techniques influenced the weed profile, and crop production of T. aman rice varieties. The study was done employing a randomized complete block design with 3 trials. The investigation comprised three aman rice cultivars and four weeds control techniques such as control, pre-emergence herbicide, early post emergence and post emergence herbicide. On research sites, ten weed types from 5 families were revealed. The grass weed Echinochloa gras-galli had the highest summed dominance ratio (SDR: 42.05%), while the sedges Scirpus mucronatus had the lowest SDR of 0.81%. Post-emergence herbicide application provided the lowest weed biomass and density at all sampling dates and produced the greatest seed yields (4.25 t ha-1), straw yield (5.41 t ha-1) and harvest index (43.87%) because of minimal crop-weed competition. In the case of interaction, BRRI dhan49 coupled with post emergence herbicide attained maximum output (4.80 t ha-1) followed by BRRI dhan49 with early post emergence. Due to ability for reducing weeds population, usage of post emergence herbicide could be considered as an efficient weed control approach in BRRI dhan49.

Bio-efficacy of pre and post-emergence herbicides on lentil yield, weed control efficiency, weed index, nutrient uptake and economics

Lentil (Lens culinaris Medikus) is an important grain legume crop. Among all the biotic factors, weed infestation is being an adverse impact on growth, yield, nutrient uptake and economics due to lentil short stature, low branching, lack of protective canopy and it’s unable to smother the weeds. Although, applying pre emergence herbicides, in many situation early weed control herbicides are not that much efficient for attaining higher yields due to lentil is long duration crop and critical weed competition upto 40-60 DAS. Sequence use of pre and post-emergence herbicides and application of early post-emergence herbicides may help in controlling the weeds at later stages of crop growth period. To understand resources distribution in lentil a field experiment was laid out at BAU research farm, Sabour during Rabi of 2019-20 in RCBD replicated thrice with 13 treatments to assess the effect of various pre and post-emergence herbicides in lentil. Out of 13 treatments, weed free treatment produced significantly higher grain yield and haum yield and new generation herbicides application of pendimethalin fb quizalofop-ethyl + imazethapyr and oxyflurofen fb quizalofop-ethyl + imazethapyr were statistically at par with weed free treatment. Weed control efficiency, Weed index, Nutrients uptake and Economics by different weeds treatments were recorded significantly higher in pendimethalin fb quizalofop-ethyl + imazethapyr, oxyflurofen fb quizalofop-ethyl + imazethapyr and imazethapyr + imazomox at 60 DAS and at harvest. Ultimately, it can be concluded that, application of pendimethalin fb quizalofop-ethyl + imazethapyr and oxyflurofen fb quizalofop-ethyl + imazethapyr in lentil brings in enhancing grain yield and achieving more net returns, B:C ratio apart from suppressing the weeds through higher weed control efficiency and lower weed index.

Effect of Early Post-Emergence Herbicides on Photosynthetic Pigments and Yield in Greengram (Vigna radiata L.)

Aims: To study the influence of early post-emergence herbicides on photosynthetic pigments and yield in greengram.&#x0D; Study Design: Randomized Block Design.&#x0D; Place and Duration of Study: Field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore, India during summer 2022.&#x0D; Methodology: The experiment was laid out with three replications having nine treatments comprising of weedy check, different ready mix early post-emergence herbicides, two hand weedings and weed free. The chlorophyll content mg g-1 in the leaf sample was recorded at 30, 45 and 60 DAS. Grain yield and haulm yield was also calculated and expressed in kg ha-1.&#x0D; Results: Pre-emergence (PE) application of Pendimethalin 30% EC @ 1 kg a.i ha-1 on 3 DAS followed by (fb) Early post-emergence (EPoE) Imazethapyr 10% SL @ 100 g a.i ha-1 + Quizalofop-ethyl 5% EC @ 50 g a.i ha-1 (Tank mix) on 15 DAS significantly recorded highest value in all photosynthetic pigments viz., Chlorophyll a (1.105 mg g-1), Chlorophyll b (0.402 mg g-1), Total chlorophyll (1.601 mg g-1), Chlorophyll ab ratio and Carotenoids (0.413 mg g-1), whereas higher grain yield (908 kg ha-1) is achieved by the Pre-emergence (PE) application of PE Pendimethalin (30% EC) @ 1 kg a.i ha-1 on 3 DAS followed by (fb) Early post-emergence (EPoE) Propaquizafop 2.5% + Imazethapyr 3.75% ME Ready mix (RM) @ 125 g a.i ha-1 on 15 DAS.&#x0D; Conclusion: Among the early post-emergence herbicides, Imazethapyr 10% SL @ 100 g a.i ha-1+ Quizalofop-ethyl 5% EC @ 50 g a.i ha-1 (Tank mix) on 15 DAS shown significant results in all the photosynthetic pigments and Propaquizafop 2.5% + Imazethapyr 3.75% ME Ready mix (RM) @ 125 g a.i ha-1 on 15 DAS shown significant results in the yield by suppressing the weeds.

Economics of reducing Palmer amaranth seed production in dicamba/glufosinate/glyphosate‐resistant soybean

AbstractIncreased prevalence of glyphosate‐resistant (GR) weeds within agronomic cropping systems has led to the readoption of pre‐emergence (PRE) herbicides and use of multiple herbicide‐resistant soybean [Glycine max (L.) Merr.] cultivars. Herbicide programs were evaluated in the recently commercialized dicamba/glyphosate/glufosinate‐resistant (DGGR) soybean for weed control, reduction of Palmer amaranth (Amaranthus palmeri S. Watson) seed production, crop safety, and economic performance. At 35 days after pre‐emergence herbicides, acetochlor plus dicamba plus metribuzin, acetochlor/fomesafen plus dicamba, dicamba plus flumioxazin, and imazethapyr/pyroxasulfone/saflufenacil provided 80–99% control of velvetleaf (Abutilon theophrasti Medik.), Palmer amaranth, common lambsquarters (Chenopodium album L.), and Poaceae species. Evaluation at 14 days after early postemergence herbicides indicated PRE followed by (fb) POST applications of mixtures of acetochlor, dicamba, glufosinate, and glyphosate provided 80–99% weed control compared with 67–93% control in POST‐only programs. Most herbicide programs provided 83–99% control of grass and broadleaf weeds, with 85–91% weed biomass reductions at 28 days after late‐POST. The PRE fb POST programs reduced Palmer amaranth seed production by 94–99%, whereas POST‐only programs provided 75–83% reduction. In 2020, most programs provided gross profit margins ≥US$1,000 ha−1, with glufosinate fb glufosinate and imazethapyr/pyroxasulfone/saflufenacil fb acetochlor plus glufosinate providing $1,481 and $1,466 ha−1, respectively. Benefit/cost ratios ranged between 0.3 and 3.9 in 2019 due to hail but increased to 2.9–10.9 in 2020. Results of this study support use of PRE herbicides with multiple sites of action in DGGR soybean and indicate that glufosinate can provide POST control of GR Palmer amaranth.

Weed Management in Mulberry (Morus alba): A Review

Mulberry leaf is a sole food of silkworm Bombyx mori on which it feeds and produces silk called mulberry or mori silk. Due to its quality, mori silk has huge demand in national and international market and earns a valuable foreign exchange for the country. Weeds are of great menace as they interfere with production and quality of mulberry leaf and also add significant amount to the cost of cultivation. The factors which are congenial for heavy weed growth in mulberry are continuous mono-cropping, wider spacing coupled with regular application of manures and fertilizers after each crop harvest for maintenance of plantation. The reduction in production and quality of leaf has direct correlation with production of cocoons and quality silk. If losses due to weeds can be reduced by half from present level of 30-40%, leaf yield of mulberry will increase by 9-12 MT ha-1 year-1 which can be utilized to produce 55-73.5 kg ha-1 year-1 more raw silk to enhance the silk production of country. The effective weed control involves identification of weed flora, method of weed control and judicious combination of effective weed control methods. Depending upon soil type, agro climatic and ecological conditions, the nature and intensity of weed flora, their competitiveness varies. A total of 57-141 weed species belongs to 28-44 families have been reported in mulberry field across the country. Manual weeding in mulberry is an age old practice in India, but it is a tedious, expensive and time consuming. Black polyethylene mulching alone has been found economically advantageous over manual weeding in mulberry plantation. However no single method viz., manual weeding, cover crop intercropping, herbicide and mulching found effective in weed control as compared to integrated method of weed control. Spraying of pre-emergence and early post emergence herbicides keeps the mulberry plantation in weed free conditions during the early stages. At later stage, when second flush of weeds attains peak after 30 days of pruning, spraying of herbicide is not possible due to chance of residual toxicity to the silkworm. Integration of pre herbicide followed by manual weeding at later stage or integration of hand weeding after pruning followed by either cover crop intercropping or mulching may helps to reduce damage due to weed, prevent silkworm from residual toxicity of herbicide and reduces manual weeding cost to some extent. Hence a brief review was presented to find out the influence of different weed management method in mulberry.

Effect of weed management practices on the performance of 4 rice cv. Nizershail

An experiment was carried out at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during the period from July to December 2018 to study the effect of weed management practices on the performance of rice cv. Nizershail. The experiment included five weeding treatments i.e., (i) no weeding (T0), (ii) hand weeding at 15 and 35 days after transplanting (DAT) (T1), (iii) application of pre-emergence herbicide (T2), (iv) application of early post-emergence herbicide (T3), and (v) application of post-emergence herbicide (T4). The experiment was laid out in a random- ized complete block design (RCBD) with three replications. All plant and yield contributing characters (except 1000-grain weight), and yields were significantly affected by weed control approaches. The application of early post-emergence herbicide Super power 10WP (T3) showed the promising results in controlling weeds in Nizershail rice. The highest values for plant height, panicle length and grain yield (1.41 t ha−1) were obtained from apply- ing post-emergence herbicide Super power 10WP. However, application of pre-emergence herbicide (Glycel 48SL) and two hand weeding at 15 and 35 DATs gave statistically similar grain yield. The results of the study showed that fifteen weed species belonging to six families infested the experimental plots. Weed density and dry matter were significantly affected by weed con- trol methods. Weed density and dry weight were also significantly affected by weed control methods. Both early post-emergence and post-emergence herbicides could effectively control the weed density and biomass.

Evaluating herbicide programs for peanut response and weed control

AbstractField research evaluated peanut (Arachis hypogaea L.) tolerance and weed control with preemergence (PRE) followed by early postemergence (EPOST) herbicide programs: PRE pyroxasulfone, S‐metolachlor, flumioxazin, pendimethalin, ethalfluralin, diclosulam, or dimethenamid‐P, followed by EPOST application of paraquat + acetochlor + bentazon at 4 wk after PRE (WA‐PRE). The herbicides resulted in no differences in peanut injury at 2 WA‐PRE in 2019 but flumioxazin resulted in approximately two‐fold greater injury (&gt;22%) than other treatments in 2020 because of heavy rainfall at peanut cracking. Palmer amaranth (Amaranthus palmeri S.Watson) control with diclosulam was lower than with other herbicides. Carpetweed (Mollugo verticillata L.) control with S‐metolachlor and dimethenamid‐P was at least 10% lower than with pendimethalin, flumioxazin, or pyroxasulfone at 4 WA‐PRE. Palmer amaranth control 2 wk after the EPOST (WA‐EPOST) application was &gt;94% for all treatments except diclosulam. Peanut injury at 2 WA‐EPOST was ≤28% but was minimal by 8 WA‐EPOST. Overall, yield with herbicide treatments was similar to the weedfree control. A greenhouse experiment evaluated postemergence herbicide combinations for Palmer amaranth control, including 2,4‐DB, acifluorfen, imazapic, bentazon + acifluorfen, pyroxasulfone + carfentrazone, and various combinations of each. Palmer amaranth control (≥99%) was greater and biomass (≤0.3 g plant–1) was lower with acifluorfen treatments than with other treatments. The 2,4‐DB + pyroxasulfone + carfentrazone treatment provided similar control to acifluorfen treatments. The EPOST paraquat + acetochlor + bentazon combinations following an effective PRE program will effectively control Palmer amaranth in peanut. Additionally, greenhouse experiments supported the use of acifluorfen for postemergence Palmer amaranth control.

Response of herbicides in different rice varieties under wet direct-seeded ecosystem

The present study was conducted to evaluate the imazethapyr tolerant variety with different weed management methods. A field experiment was conducted in the experimental farm of the Department of Rice, TNAU, Coimbatore, Tamil Nadu during rabi season 2020 in split plot design with three replications. The treatments in main plot consisted of nine rice varieties viz HTM-N 22, N 22, Anna (R) 4, CO 53, CO 51, ADT 53, ADT 37, ADT 43 and ADT 45. In sub-plot weed management methods included early post-emergence herbicide application of imazethapyr @ 75 g ai/ha at 30 DAS, early post-emergence herbicide application of bispyribac sodium @ 25 g ai/ha at 15-20 DAS, pre-emergence herbicide application of pretilachlor @ 0.75 kg ai/ha at 8 DAS followed by early post-emergence herbicide application of bispyribac sodium @ 25 g ai/ha at 20-25 DAS, hand weeding twice at 20 and 40 DAS and un-weeded check. There were marked variations in the effect of various weed management practices in direct-seeded rice. In weed management methods, pre-emergence herbicide application of pretilachlor @ 0.75 kg ai/ha at 8 DAS followed by early post-emergence herbicide application of bispyribac sodium @ 25 g ai/ha at 20-25 DAS effectively controlled the weeds in wet direct-seeded rice ecosystem. Among the varieties tested, HTM-N 22 and N 22 only survived with the early post-emergence herbicide application of imazethapyr @ 75 g ai/ha at 30 DAS. The varieties HTM-N 22 and N 22 can be utilised for rice breeding programme for the development of herbicide tolerant varieties.

Effect of weed management practices on growth and yield of transplanted rice (Oryza sativa L.) under system of rice intensification

A field experiment was carried out in wetland farms of TNAU, Coimbatore during summer 2021 to evaluate efficient weed management practices for transplanted rice under the System of Rice Intensification (SRI). The treatments consisted of different combinations of weed management practices including herbicides viz., butachlor 1.25 kg ha-1 and bispyribac sodium 40 g ha-1, cono weeding and hand weeding and were compared with unweeded control. The predominant weed flora present in the experimental field was Echnichloa colona (L.), Echnichloa crusgalli (L.), among grasses, Cyperus difformis (L.), among sedges and Eclipta alba (L.), Ammania baccifera (L.), among broad leaved weeds. The results revealed that application of early post emergence herbicide bispyribac sodium @ 40 g ha-1 at 15 DAT + cono weeding at 30 and 40 DAT recorded lesser weed density (4.18, 2.88 no. m-2 at 40 and 60 DAT), weed dry weight (3.20, 1.61 g m-2 at 40 and 60 DAT) and higher weed control efficiency (82.1 and 93.6 per cent at 40 and 60 DAT) which resulted in increased number of productive tillers m‑2 (445) and filled grains per panicle (176). Application of early post emergence herbicide bispyribac sodium @ 40 g ha-1 + cono weeding at 30 and 40 DAT recorded higher grain and straw yields of 6975 kg ha-1 and 9905 kg ha-1, respectively. This treatment was on par with application of early post emergence herbicide bispyribac sodium 40 g ha-1 + cono weeding at 30 DAT and hand weeding at 40 DAT.

Optimization of Spray Fluid for Herbicide Application for Drones in Irrigated Maize (Zea mays L.)

A field experiment was conducted in a randomized complete block design to screen the optimum spray fluid of herbicide application for drone based on visual toxicity and weed control efficiency in maize (Zea mays L.) during the summer season (March 2021) at eastern block farms of Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu. Three herbicide treatments namely Atrazine, Tembotrione and 2, 4-D with recommended dosages, 75% and 125% as pre-emergence herbicides applied on 3 days after, early post-emergence herbicides applied on 15 days after sowing and post-emergence applied on 25 days after sowing respectively. Totally thirty treatments with different spray fluids such as 500, 400, 300, 200, 100, 80, 60, 40, 30 L ha-1 and 20 L ha-1 were replicated three times. The study revealed that T5- Recommended dosage of pre emergence Atrazine – early post emergence Tembotrione – post emergence 2, 4-D (spray fluid 100 L of water ha-1),T6- Recommended dosage of pre emergence Atrazine – early post emergence Tembotrione–post emergence 2, 4-D (spray fluid 80 L of water ha-1), T7- Recommended dosage of pre emergence Atrazine – early post emergence Tembotrione – post emergence 2, 4-D (spray fluid 60 L of water ha-1) and T8- Recommended dosage of pre emergence Atrazine – early post emergence Tembotrione – post emergence 2, 4-D (spray fluid 40 L of water ha-1) produced the best results with respect to phytotoxicity and weed control efficiency. Based on the results it was concluded that the application of spray fluid 80 L ha-1 was optimum for herbicide application through drones with recommended dosage pre emergence Atrazine 1 kg a.i ha-1 on 3 days after sowing – early post emergence Tembotrione 120 g a.i ha-1 on 15-20 days after sowing - post emergence 2, 4-D 1 kg a.i ha-1 on 30 - 35 days after sowing.

Allelopathic and Herbicidal Effects of Crude Extract from Chromolaena odorata (L.) R.M.King and H.Rob. on Echinochloa crus-galli and Amaranthus viridis.

The present study was aimed at investigating the allelopathic effects of a crude extract from Chromolaena odorata (L.) R.M.King and H.Rob. (Siam weed). The effects of 70% crude ethanol extract from the whole plant, leaf, stem, and root on the germination and growth of Echinochloa crus-galli and Amaranthus viridis seedlings were evaluated using Petri-dish tests under laboratory conditions. Crude extracts from the leaf showed the highest inhibitory activity. The leaf extract (OR) was further separated by sequential solvent extraction to provide hexane (HX), ethyl acetate (ET), and butanol (BU) fractions, which were also evaluated using Petri-dish tests. The hexane fraction was significantly the most active; therefore, it was selected for formulation in a concentrated suspension and tested for its herbicidal characteristics. The formulation showed greater early post-emergence than post- and pre-emergence activities, respectively. The physiological mechanism of the formulation was tested against E. crus-galli and showed that chlorophyll a and b and the carotenoid contents of the leaf dramatically decreased when the concentration was increased, suggesting its ability to disrupt the process of photosynthesis. As thiobarbituric acid reactive substances also occurred in the leaf of E. crus-galli, this suggests lipid peroxidation and cell disruption. These results represent the possibility that C. odorata extract contains inhibitory compounds with herbicidal activity and could be used as an early post-emergence herbicide for weed control.