Pre-emergence Application Research Articles

Grass Weed Control and Rice Response with Tetflupyrolimet-containing Programs

ABSTRACT Tetflupyrolimet is the first herbicide with a novel site of action labeled preemergence (PRE) and early postemergence for use in agronomic crops in the last three decades. Direct-seeded paddy rice field experiments were conducted near Stuttgart on a silt loam soil, AR, and Keiser on a clay soil, AR, to evaluate tetflupyrolimet-containing herbicide programs in comparison to commercial standards in conventional, imidazolinone-, and quizalofop-resistant rice systems. Additionally, a furrow-irrigated rice experiment was conducted near Colt, AR, on a silt loam soil, and Keiser to ensure clomazone and tetflupyrolimet mixtures compared to commercial standards. Twelve commonly planted rice cultivars were also evaluated in response to a single PRE or postemergence (POST) (2- to 3-leaf rice) application of tetflupyrolimet at 200 and 400 g ai ha-1 in a paddy rice system, near Colt. When averaged over soil texture and site-year, all herbicide programs, provided ≥98% barnyardgrass control at 56 d after (DA) the last application. Visible rice injury varied for each rice system. Still, injury rarely differed amongst herbicide programs, except at a single evaluation timing in the conventional (7 DA 3- to 4-leaf applications) and quizalofop-resistant (preflood) systems. All 12 rice cultivars displayed a high tolerance level to a single PRE or POST application of tetflupyrolimet at 200 and 400 g ai ha-1. No visible injury, stand loss, or negative impact on rice maturity or reduced grain yield was observed for any cultivar. Tetflupyrolimet will be an effective alternative SOA in a program approach for barnyardgrass while maintaining excellent rice crop safety.

Seleção de herbicidas pré-emergentes para o trigo

ABSTRACT Weed control is a challenge in crop management due to the limited number of registered herbicides, especially for preemergent application. This study aimed to investigate the selectivity of pre-emergent herbicides with different mechanisms of action for wheat. The experiment consisted of two stages: the first involved screening under greenhouse conditions, and the second assessing the selected treatments under field conditions, with a focus on crop yield. Plant phytointoxication, crop stand, and shoot dry weight were assessed in the greenhouse experiment, and tillering, crop stand, plant height, canopy closure, yield, 1000-grain weight, and hectoliter weight in the field. Under greenhouse conditions, [imazapic + imazapyr], pendimethalin, isoxaflutole, florpyrauxifen, and halosulfuron-methyl produced the best results and were selected for the field experiment. Florpyrauxifen was the only herbicide that was selective both in greenhouse and field experiments. Isoxaflutole and trifluralin did not damage wheat in any of the field evaluations. Despite reducing crop performance in some assessments, pendimethalin and flumioxazin provided yield, hectoliter weight, and 1000-grain weight results equivalent to the herbicide-free control. Florpyrauxifen (1.08 g ha-1) was the most promising herbicide. Trifluralin (900 g ha-1), pendimethalin (1750 g ha-1), isoxaflutole (60 g ha-1), and flumioxazin (40 and 60 g ha-1) also produced grain yields equivalent to the control without herbicide.

Productivity of summer greengram (Vigna radiata) under different nitrogen levels and weed management practices

A field investigation was carried out during summer season, 2022 at ARS, Faculty of Agricultural Sciences, SOADU, Bhubaneswar to study the effect of nitrogen levels and weed management practices on Weed growth and productivity of summer greengram (Vigna radiata L.). The experiment was laid out in split plot design with three replications comprising fifteen treatment combinations. Treatments consisted of three nitogen levels in main plot and five weed management practices in subplot. The predominant weeds in the experimental plots were Poa annua, Digitaria sanguinalis, Echinochloa colona, Cleome viscose, Ageratum conyzoides, Portulaca oleracea, and Melochia corchorifolia. Results revealed that among the different levels of nitrogen, the lowest density and dry weight of grasses, broadleaved and total weeds was recorded with application of 75% N. Among the weed management practices, two hand weeding at 15 and 30 DAS, registered significantly lowest density and biomass of all categories of weeds as well as total weeds and it was closely followed by pre-emergence application of ready-mix pendimethalin + imazethapyr 0.75 kg/ ha at 45 DAS. Application of 125% N registered highest seed (832.30 kg/ ha) and stover yield (2189.64 kg/ ha) and along with high yield attributing characters like number of pods/ plant (25.54) and seeds/ pod (6.39) as compared to others and it was at par with application of 100% N. Among the weed management practices, two hand weeding at 15 and 30 DAS recorded highest seed yield (930.56 kg/ ha) and stover yield (2397.11 kg/ ha) of greengram along with higher yield attributing characters like number of pods/ plant (27.73), seeds/ pod (7.29) and number of branches/ plant (8.94) and it was closely followed by pre-emergence application of ready-mix pendimethalin + imazethapyr at 0.75 kg/ ha.

Evaluating shifts in species distribution following herbicide and fertilizer applications for smutgrass (Sporobolus indicus) control in bahiagrass

Abstract Novel management strategies for controlling smutgrass have potential to influence sward dynamics in bahiagrass forage systems. This experiment evaluated population shifts in bahiagrass forage following implementation of integrated herbicide and fertilizer management plans for controlling smutgrass. Herbicide treatments included indaziflam applied preemergence (PRE), hexazinone applied postemergence (POST), a combination of PRE + POST herbicides, and a nonsprayed control. Fertilizer treatments included nitrogen (N), nitrogen + potassium (N+K), and an unfertilized control. The POST reduced smutgrass coverage regardless of PRE or fertilizer application by the end of the first season and remained low for the three-year duration of the experiment (P < 0.01). All treatments, including nontreated controls, reduced smutgrass coverage during year 3 (P < 0.05), indicating that routine harvesting to remove the biomass reduced smutgrass coverage. Bahiagrass cover increased at the end of year 1 with POST (P < 0.01) but only the POST + fertilizer treatment maintained greater bahiagrass coverage than the nontreated control by the end of year 3 (P < 0.05). Expenses associated with the POST + fertilizer treatment totaled $348 ha-1 across the three-year experiment. Other smutgrass control options could include complete removal of biomass (hay production) and pasture renovation, which can cost threefold or greater more than POST + fertilizer treatment. Complete removal of biomass may reduce smutgrass coverage by removing mature seedheads, but at a much greater expense of $2,835 to $5,825 ha-1 depending on herbicide and fertilizer inputs. Bahiagrass renovation is $826 ha-1 in establishment costs alone. When pasture production expenses are included for two seasons post-renovation, the total increases to $1,120 ha-1 across three seasons. The importance of hexazinone and fertilizer as components of smutgrass control in bahiagrass forage was confirmed in this study. Future research should focus on the biology of smutgrass and the role of a PRE in a long-term, larger-scale forage system.

Sensitivity of difficult‐to‐control Palmer amaranth accessions to fluridone and diflufenican

AbstractPalmer amaranth (Amaranthus palmeri S. Watson) has evolved resistance to herbicides targeting nine sites of action. Phytoene desaturase‐inhibiting herbicides remain among the few sites of action that are still effective in controlling Palmer amaranth. Greenhouse experiments were conducted to evaluate the effectiveness of fluridone and diflufenican in controlling difficult‐to‐control Palmer amaranth accessions collected in Arkansas from 2016 to 2022, to quantify the response of three accessions that exhibited low sensitivity to both herbicides, and to evaluate the effectiveness of photosystem II inhibitors alone and with fluridone or diflufenican on three accessions. At 14 days after a preemergence application, Palmer amaranth control with fluridone and diflufenican ranged from 42% to 100% and 33% to 99% across 23 accessions, respectively. Three accessions required 10.2 to 26.7 times more fluridone than the susceptible Palmer amaranth standard based on LD50 values (where LD50 is the lethal dose to kill 50% of the population), with less than 50% mortality achieved with a 1x herbicide rate for two of the three accessions. For diflufenican, the LD50 values for the three accessions were 3.9–18.5 times greater than the susceptible standard. An additive response for mortality and biomass reduction resulted from adding fluometuron to fluridone at all rates tested. An additive or sometimes a synergistic response occurred with the combinations of metribuzin plus diflufenican. Overall, fluridone exhibited higher efficacy than diflufenican for most accessions tested. While phytoene desaturase‐inhibiting herbicides remain an effective control option for most Palmer amaranth accessions, herbicide mixtures targeting multiple sites of action remain essential for delaying resistance and obtaining effective control of this problematic weed.

Impact of Low-dose Herbicides on Weed Dynamics and Nutrient Removal by weeds in Transplanted Rice

The objective of this study is to find out the effect of low-dose herbicides on growth and yield in transplanted rice. A field experiment was conducted during the Kuruvai season (June – September 2023) at Experimental Farm, Department of Agronomy, Faculty of Agriculture, Annamalai University, Annamalai Nagar, Chidambaram, Tamil Nadu, India. The experiment was laid out in a randomized block design with nine treatments and three replications. The treatments consisted of T1 - unweeded control, T2 - Twice hand weeding @ 20 and 40 DAT, T3 - PE application of Pretilachlor 50% EC @ 0.75 kg ha-1 on 3 DAT alone, T4 - PE application of Pretilachlor 50% EC @ 0.75 kg ha-1 on 3 DAT alone + One hand weeding at 30 DAT, T5 - PE application of Metsulfuron-methyl 10% + Chlorimuron-ethyl 10% WP @ 20 g ha-1 on 3 DAT alone, T6 - PE application of Metsulfuron-methyl 10% + Chlorimuron-ethyl 10% WP @ 20 g ha-1 on 3 DAT + One hand weeding at 30 DAT, T7 - PoE application of Fenoxaprop-p-ethyl 6.9% EC @ 60 g ha-1 on 21 DAT alone, T8 - PE application of Pretilachlor 50% EC @ 0.75 kg ha-1 on 3 DAT + PoE application of Fenoxaprop-p-ethyl 6.9% EC @ 60 g ha-1 on 21 DAT, T9 - PE application of Metsulfuron-methyl 10% + Chlorimuron-ethyl 10% WP @ 20 g ha-1 on 3 DAT + PoE application of Fenoxaprop-p-ethyl 6.9% EC @ 60 g ha-1 on 21 DAT. Among these treatments, it is observed that the pre-emergence application of Metsulfuron-methyl 10% + Chlorimuron-ethyl 10% WP @ 20 g ha-1 on 3 DAT + Post-emergence application of Fenoxaprop-p-ethyl 6.9% EC @ 60 g ha-1 on 21 DAT (T9) had effectively decreased total weed count, weed dry matter production and nutrient removal by weeds. This led to an improvement in crop development and production.

Use of a Capsule Suspension Formulation of S-metolachlor in Fenclorim-treated Rice

Abstract As herbicide resistance continues to render commonly used rice herbicides ineffective, alternative sites of action are paramount to maintaining yield and producer profitability. Combining a slow-release formulation and a fenclorim seed treatment might allow the safe use of S-metolachlor in rice. Experiments were initiated in 2022 and 2023 near Colt, AR, on a silt loam soil to evaluate crop safety using a capsule suspension (CS) formulation of S-metolachlor and a fenclorim seed treatment in rice. The first experiment assessed the tolerance of two cultivars (Diamond and DG263L) to three rates (0.42, 0.84, 1.68 kg ai ha-1) of a CS S-metolachlor at a delayed preemergence (DPRE) application timing in conjunction with a fenclorim seed treatment. The second experiment evaluated a 1- to 2-leaf (EPOST) application of a CS S-metolachlor at 0.56 and 1.12 kg ai ha-1 to fenclorim-treated rice. Fenclorim reduced injury and partially protected rice yield when S-metolachlor was applied DPRE at 1.68 kg ai ha-1 in both years. However, in one year under adverse conditions, rice yields were only 65% and 66% of the nontreated control for fenclorim-treated Diamond and DG263L, respectively. An EPOST application of S-metolachlor at 1.12 kg ai ha-1 resulted in 44 to 51% visible injury 35 d after treatment. Relative rice yields were 88% and 89% of the nontreated weed-free treatment in 2022 and 2023, respectively. Fenclorim provided enhanced crop safety at both the 0.84 and 1.68 kg ai ha-1 rates of S-metolachlor. However, the potential for reduced yield can occur when unfavorable conditions occur soon after application. An EPOST application timing of CS S-metolachlor at 0.56 kg ai ha-1 may be a viable option in rice, but 1.12 kg ai ha-1 is too high on a silt loam soil, resulting in significant rice injury.

Weed Management Effects on Weed Dynamics, Yield and Economics of Spring Maize at Dang, Nepal

Weeds pose a significant challenge in maize fields in the Dang district, leading to a substantial 52% reduction in yield. Hence, this study was conducted in Satbariya village of Dang, Nepal, in 2023 to evaluate the impact of various weed management practices on weed dynamics, growth, and yield of spring maize. The experiment included seven treatments: a weedy check, weed-free plot, pre-emergence application of atrazine at 1.25 a.i. kg/ha (AtPrE), post-emergence application of atrazine at 1.25 a.i. kg/ha (AtPoE), manual weeding at 30 DAS, mini-tiller at 30 DAS, and LaPoE (tembotrione 42% SC + atrazine 50% WP) applied as post-emergence. The Subarna variety of maize was chosen for the study. Fifteen weed species from seven different families were identified in the experimental area. Specific morphological and phenological parameters, such as plant height and days to tasseling and silking, were not significantly influenced by the weed control methods. However, significantly lower weed density and biomass were observed in the weed-free plot and LaPoE. Similarly, weed-free plots and LaPoE exhibited significantly higher weed control efficiency (WCE) and weed control index at both 45 and 60 DAS, leading to a lower weed index (0.00–16.71%) and more effective weed control. Concerning the yield parameters, cob length, number of kernels per row, and 1000-grain weight were significantly higher in weed-free plots, followed by LaPOE, and the highest grain and biological yield were observed in weed-free plot (6.14–15.18 tons/ha) and LaPoE (5.12–13.32 tons/ha). Moreover, the benefit-cost ratio and net return were observed to be highest with LaPoE. This study suggests that LaPoE can be an effective and economical weed management strategy for increasing maize yield and profitability. Further research could explore the long-term effects of using LaPoE on weed control and crop productivity.

Complementary activity of Trifludimoxazin and Saflufenacil when used in combination for postemergence and residual weed control

Abstract Trifludimoxazin is a new herbicide that inhibits protoporphyrinogen oxidase and is targeted for commercial market introduction in North America, South America, and Asia. It will be available both as a standalone product and in a 1:2 mixture with saflufenacil. The herbicide is intended for use in preplant burndown (PPBD) and preemergence applications in cereal, corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and pulse crops to control a variety of annual broadleaf and grass weed species. Additionally, it is planned to be used in tree crops, oil-palm (Elaeis quineensis Jacq.), and non-crop areas. In this study, we meticulously evaluated the performance and effectiveness of both the standalone herbicide and the innovative mixture concept in combating prevalent weeds commonly encountered in corn and soybean fields. Our findings revealed that both products exhibited exceptional efficacy, significantly reducing the presence of these troublesome weeds. Furthermore, the mixture concept not only demonstrated commendable soil mobility but also showcased impressive residual activity, positioning it as a powerful tool for sustainable weed control. These promising effects are further substantiated by our comprehensive ADME (Adsorption-Distribution-Metabolism-Extraction) studies, which provide insight into the behavior and longevity of the herbicides in the agricultural ecosystem.

Drone-assisted herbicide optimization for energy efficiency, weed control and economics in transplanted rice (Oryza sativa)

The experiment was conducted during summer and rainy (kharif) seasons of 2021 and 2022 at Agricultural Research Station (Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu), Bhavanisagar, Tamil Nadu to evaluate the efficiency, economics and energetics of drone-based herbicide spray (fluid) application in transplanted rice (Oryza sativa L.). During the experiment the application of pre-emergence and post-emergence herbicides was done using drone and knapsack sprayer to assess the weed control efficiency (WCE). Treatments included 3 herbicide combinations, viz. pyrazosulfuron ethyl as pre-emergence (PE); pyrazosulfuron ethyl as pre-emergence (PE) fb bispyribac sodium as PoE; and pyrazosulfuron ethyl as PE fb metsulfuron methyl + chlorimuron ethyl as PoE; and 4 spray fluids applied using drone and knapsack sprayer (25, 37.5, 75 and 500 litre/ha). Weed free and unweeded check plot were used as reference for calculating WCE. Application of pyrazosulfuron ethyl fb bispyribac sodium using knapsack sprayer reduced weed density from 77.74–86.45% and weed dry weight from 89.60–91.40% over unweeded plot. Moreover, it was found on par with drone application of 37.5 litre/ha using herbicides during both the seasons. Interaction effect between herbicides and drone spray fluids was found to be non-significant. Pyrazosulfuron ethyl fb bispyribac sodium application through knapsack sprayer (500 litre/ha) and drone (37.5 litre/ha) produced higher grain yield and straw yield. Higher net return, benefit: cost ratio (2.49 and 2.40), energy-use efficiency (13.44 and 13.40 MJ) and energy productivity (0.414 and 0.416 kg/MJ) were noticed with drone application of pyrazosulfuron ethyl fb bispyribac sodium using 37.5 litre/ha spray fluid in both the seasons. From the experiment, drone application of pyrazosulfuron ethyl fb bispyribac sodium with spray volume of 37.5 litre/ha was found as an effective strategy to manage weeds in transplanted rice and more advantageous in terms of energy-use efficiency and profitability.

Palmer amaranth (Amaranthus palmeri) Control in Furrow-Irrigated Rice with Fluridone

Abstract Herbicide-resistant Palmer amaranth is creating additional challenges for producers choosing to adopt a furrow-irrigated rice production system due to the absence of a sustained flood, enabling extended weed emergence. Fluridone has been shown to control Palmer amaranth effectively in cotton production systems and was recently registered for use in rice. Experiments were initiated in 2022 and 2023 to evaluate 1) Palmer amaranth control and rice tolerance to preemergence- and postemergence-applied fluridone at a 0.5x (84 g ai ha-1) and 1x rate (168 g ai ha-1) on a silt loam soil and 2) the effect of various herbicide programs containing fluridone on Palmer amaranth biomass, seed production, and rough rice grain yield. Preemergence applications of fluridone at a 1x rate in combination with clomazone resulted in 84% control of Palmer amaranth 21 d after treatment (DAT). Fluridone, in combination with clomazone preemergence, caused up to 36% rice injury 21 DAT; however, early season injury did not negatively affect rice yields. Palmer amaranth biomass and fecundity were reduced with herbicide programs that included fluridone plus florpyrauxifen-benzyl, and, in some instances, there was no Palmer amaranth biomass or seed production following multiple applications of both herbicides. Fluridone- and florpyrauxifen-benzyl-based herbicide programs achieved effective control of Palmer amaranth when applied timely, but injury to hybrid rice is enhanced with preemergence applications of fluridone that are not permitted with the current label.

Italian Ryegrass Control Using a Capsule Suspension Formulation of S-metolachlor in Fenclorim-treated Wheat

Abstract Italian ryegrass control is one of the most significant limitations in wheat production in the U.S. today. Resistance to Herbicide Resistance Action Committee (HRAC)/Weed Science Society of America (WSSA) Groups 1, 2, and 9 in Arkansas have further complicated postemergence control, while residual herbicides still show effective weed control. One problem is the potential of HRAC/WSSA Group 15 herbicides to injure wheat when applied preemergence, indicating the need for a herbicide safener. A series of experiments were conducted in Fayetteville, AR, to evaluate crop tolerance and Italian ryegrass control using a capsule suspension formulation of S-metolachlor in conjunction with fenclorim-treated wheat. Experiments were conducted as a two-factor factorial with S-metolachlor applied at three rates (0.37, 0.74, and 1.12 kg ai ha-1) and a microencapsulated formulation of acetochlor at 1.05 kg ai ha-1, and three rates of a fenclorim seed treatment at 0, 0.5, and 2.0 g ai kg-1 of seed. Separate experiments utilized either a preemergence (PRE) or a delayed-preemergence (DPRE) application timing. In both experiments, S-metolachlor at 0.74 and 1.12 kg ai ha-1 provided 77 to 96% control of Italian ryegrass by preharvest, whereas acetochlor only provided 49 to 72% control. Visible wheat injury from PRE applications ranged from 7 to 49% for all treatments 21 d after treatment (DAT), with a reduction in injury when fenclorim-treated wheat was used for both the 0.74 and 1.12 kg ai ha-1 rate of S-metolachlor. In the DPRE experiments, wheat injury ranged from 5 to 16% 21 DAT with no noticeable safening from the presence of fenclorim at any herbicide rate. The results of these experiments indicate that a DPRE application using a CS formulation of S-metolachlor would be more favorable for producers to mitigate the potential for injury to wheat while providing Italian ryegrass control. Additionally, at the DPRE application timing, fenclorim is unnecessary for S-metolachlor to be safely applied at the rates evaluated.

Bio-efficacy of herbicides on weeds in direct-seeded rice in Konkan region of India

Rice cultivation by direct seeding is viewed as both cost and labor-saving practice and becoming popular alter- native to transplanting. Weeds are a more serious problem in DSR than in transplanted rice. The field experimen- tal is conducted to evaluate the bio -efficacy of pre and post – emergence herbicides, hand-weeding on weed con- trol, yield components, yield and their economic feasibility for cost effective weed control in direct seeded rice. The experiment was laid out in randomized block design with three replications and seven treatments, viz. Pre-emer- gence oxadiargyl 80% WP @ 100 g/ha, Pre-emergence oxadiargyl 80% WP @ 100 g/ha fb HW at 30 DAS, oxadiargyl 80% WP (PE) @ 100 g/ha fb Post-emergence bispyribac- Na @ 25 g/ha at 25 DAS, Pre-emergence oxadiargyl 80% WP @ 100 g/ha fb Post-emergence metasulfuron- methyl + chlorimuron – ethyl @ 4 g/ha at 25 DAS, Pre-emergence oxadiargyl 80% WP @ 100 g/ha fb Post-emergence carfentrazone ethyl 40% @ 25 g/ha at 25 DAS. Weed density under weedy check (WC) situation showed that monocot weeds (grasses and sedges) were more pre-dominant wherein grasses and sedges constituted 74.80% and 11.48%, respectively, BLWs 14.20% of total weed density at 60 DAS of crop. Amongst the herbicide treatments, application of Oxadiargyl (PE) @ 100 g/ha fb HW at 30 DAS recorded significantly lowest number of weeds/m2, dry weight/m2. The highest grain yield (4.02 t/ha) and benefit cost (1.48) were recorded with the pre-emergence application of Oxadiargyl (PE) @ 100 g/ha fb HW at 30 DAS.

Influence of Grass Pea Residues Extract on Weed Control Efficacy and Performance of Boro Rice

The agriculture sector is constantly adopting environmentally friendly and sustainable methods to reduce the harmful effects of herbicides on crop production. In this respect, an experiment was conducted at the Agronomy Field Laboratory (AFL), Bangladesh Agricultural University (BAU), Mymensingh to assess the allelopathic effects of grass pea crop residues on weed suppression and the growth performance of Boro rice from December 2021 to May 2022. The experiment consisted of four cultivars of Boro rice i.e. BAU dhan3, BRRI dhan28, BRRI dhan81, BRRI dhan96 along with four different treatments of weed control viz. no extract and no weeding (control), hot water extract of Grass pea residues as pre-emergence application at 3 DAT (days after transplanting), hot water extract of Grass pea residues as pre-emergence application at 3 DAT+ post- emergence at 10 DAT, hand weeding 3 times at 15, 30 and 45 DAT. The highest weed growth was noticed when no extract was added and the lowest was found when three times hand weeding was performed. The highest number of effective tillers (NET) hill-1, number of spikelets panicle-1 (NSP) and grain yield (GY), straw yield (SY) and biological yield (BY) were recorded from the rice variety BAU dhan3. The highest NET hill-1, NSP, 1000-grain weight (TGW), GY, SY and BY were recorded from three hand weeding which was followed by hot water extract of grass pea as pre-emergence application at 3 DAT+ post-emergence application at 10 DAT. From the interaction it is observed that the highest NET hill-1, NSP, SY and BY were obtained from BAU dhan3 with three hand weeding which was followed by BAU dhan3 with hot water extract of grass pea as pre-emergence application at 3 DAT+ post-emergence application at 10 DAT. The findings of this study reveal that hand weeding, followed by the application of grass pea crop residues, effectively suppresses weed growth. Our research suggested leveraging the allelopathy-weed inverse relationship to address weed problems. This approach holds significant promise for weed management in the twenty-first century. J Bangladesh Agril Univ 22(3):360-368, 2024

The Impact of Integrated Weed Management Practices on Nutrient Uptake in Rice (Oryza sativa L.)

The study investigated the impact of integrated weed management practices on nutrient uptake in rice (Oryza sativa L.) and weeds at 90 days after transplanting (DAT) over the 2022 and 2023 growing seasons at the Crop Research Centre (CRC) farm of Sardar Vallabhbhai Patel University of Agriculture and Technology, Meerut. Various weed control strategies, including the application of pre-emergence and post-emergence herbicides combined with manual weeding, were evaluated for their effectiveness in enhancing the uptake of essential nutrients such as nitrogen (N), phosphorus (P), and potassium (K) by rice, while also reducing nutrient loss to weeds. Among the strategies tested, the combination of Pyrazosulfuron at 150 g active ingredient per hectare (a.i. ha⁻¹) as a pre-emergence herbicide and Penoxsulam at 22 g a.i. ha⁻¹ as a post-emergence herbicide, supplemented with one manual weeding at 40 DAT, proved to be the most effective. This approach resulted in the highest nutrient uptake by rice and the lowest nutrient uptake by weeds. In this treatment, nitrogen uptake in the rice grains reached 62.7 kg per hectare in 2022 and 67.4 kg per hectare in 2023, significantly outperforming other treatments. The weed-free treatment, which involved complete weed eradication, also demonstrated high nutrient absorption, highlighting the importance of thorough weed control for optimal rice growth. Conversely, the untreated weedy check, where no weed control was implemented, led to the highest nutrient uptake by weeds, severely limiting the availability of nutrients for the rice crop. Manual weeding alone, without the use of herbicides, showed moderate effectiveness but was less efficient compared to the integrated approach combining herbicides and hand weeding.

Discovering Novel Bioherbicides: The Impact of Hemp-derived Phytocannabinoid Applications on Zea mays L. and Relevant Weeds

In addition to competition, phytotoxic plant metabolites contribute to the weed-suppressing properties of cover crops, which could be the basis for the development of novel bioherbicides. We investigated the impact of five Cannabis sativa L. -derived neutral phytocannabinoids and an aqueous C. sativa tissue extract (HE) at six concentrations on the germination rate (GR) and seedling root length (RL) of Zea mays L., two monocotyledonous and two dicotyledonous weed species in laboratory Petri dish bioassays. Additionally, the effect of pre-emergence applications of HE, cannabidiol (CBD), and cannabidivarin (CBDV) formulations on GR and shoot dry matter (SDM) were examined in greenhouse pot studies. The effects of phytocannabinoids and HE were analyzed in dose-response curves. For the highest rates, the effects on GR, RL and SDM were calculated by ANOVA and HSD test (p < 0.05). HE exhibited the greatest suppression on GR and RL for all plant species in the Petri dish bioassay, with RGR, RL exceeding −90%. Phytocannabinoids reduced mainly RL of all plants and decreased the GR of most weed species. Effects varied among plants and phytocannabinoids, with CBDV and CBD showing similar high inhibitory effects on RL as HE in the Petri dish bioassay. All pre-emergence applications resulted in a positive RGR across all studied plants and in a positive RSDM in Z. mays and Echinochloa crus-galli (L.) P. Beauv, whereas in the other weed species the RSDM was negative. In conclusion, phytocannabinoids play a major role in weed suppression of HEs. CBDV and CBD are the most promising candidates for bioherbicide development especially against annual dicotyledonous weed species.

Discovering new mode-of-action pesticide leads inhibiting protein-protein interactions: example targeting plant O-acetylserine sulfhydrylase.

The widespread evolution of pesticide resistance poses a significant challenge to current agriculture, necessitating the discovery of molecules with new modes of action. Despite extensive efforts, no major molecules with new modes of action have been commercialized for decades. Most pesticides function by binding to specific pockets on target enzymes, enabling a single target site mutation to confer resistance. An alternative approach is the disruption of protein-protein interactions (PPI), which require complementary mutations on both interacting partners for resistance to occur. Thus, our aim is the discovery and design of small-molecule inhibitors that target the interface of the PPI complex of O-acetylserine sulfhydrylase (OASS) and serine acetyltransferase (SAT), key obligatory interacting plant enzymes involved in the biosynthesis of the amino acid cysteine. By employing in silico filtering techniques on a virtual library of 30 million small molecules, we identified initial hits capable of binding OASS and interfering with its interaction with a peptide derived from SAT with a half-maximal inhibitory concentration (IC50) of 34 μm. Subsequently, we conducted molecular chemical optimizations, generating an early lead molecule (PJ4) with an IC50 value of 4 μm. PJ4 successfully inhibited the germination of Arabidopsis thaliana seedlings and inhibited clover growth in a pre-emergence application at an effective concentration of 4.6 kg ha-1. These new compounds described herein can serve as promising leads for further optimization as herbicides with a new mode-of-action. This technology can be used for discovering new modes of action chemicals inhibiting all pest groups. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Synthesis and biological profile of substituted hexahydrofuro[3,4-b]furans, a novel class of bicyclic acyl-acyl carrier protein (ACP) thioesterase inhibitors.

Weed control is a significant challenge for farmers around the globe. Of the various methods available for combatting weeds, small molecules remain the most effective and versatile technology to date. In the search for novel chemical entities with new modes of action toward herbicide-resistant weeds, we have investigated hexahydrofuro[3,4-b]furan-based acyl-acyl carrier protein (ACP) thioesterase inhibitors inspired by X-ray co-crystal structure-based modeling studies. By exploiting scaffold hopping concepts and molecular modeling studies we were able to identify new hexahydrofuro[3,4-b]furan-based lead structures showing promising activity in vivo against commercially important grass weeds in line with strong target affinity. The present work covers a series of novel herbicidal lead structures that possess a hexahydrofuro[3,4-b]furan scaffold as a structural key feature, carrying ortho-substituted aryloxy side chains. Based on an optimized synthetic approach a broad structure-activity relationship (SAR) study was carried out. The new compounds emerging from our modeling-inspired structural variations show good acyl-ACP thioesterase inhibition in line with promising initial herbicidal activity. Glasshouse trials showed that the hexahydrofuro[3,4-b]furans outlined herein display good control of cold and warm season grass-weed species in pre-emergence application. Remarkably, some of the novel acyl-ACP thioesterase-inhibitors also showed promising efficacy against warm season weeds that are difficult to control. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Productivity and Profitability of Indian Mustard as affected by Integrated Weed Management

Background: Weed infestation is a primary cause of reduced yields, with estimated losses ranging from 10-70% due to crop-weed competition in Indian mustard. Therefore, it is essential to implement effective weed control measures to optimize the crop's yield potential. A combination of herbicides with manual, culturaland mechanical approaches is desirable to achieve optimal weed control. Therefore, a field experiment was carried out to evaluate the effect of integrated weed management on the productivity and profitability of Indian mustard. Methods: The experiment was conducted at the Agronomy Main Research Farm, College of Agriculture, Orissa University of Agriculture and Technology (OUAT), Bhubaneswar during rabi season of 2021-22 and 2022-23. It consisted of eight treatments in a randomized block design (RBD) with three replications. Result: Pendimethalin 0.75 kg ha-1 fb straw mulch 5 t ha-1 controlled the mixed flora of weeds which resulted in the lowest weed density, weed dry weight, weed index and highest weed control efficiency which resulted in the highest grain yield and stover yield of mustard. Pre-emergence application of pendimethalin 0.75 kg ha-1 fb straw mulch 5 t ha-1 registered the highest benefit-cost ratio.

Weed growth and productivity of green gram (Vigna radiata L.) under integrated weed management practices

Green gram is a short-duration crop that requires initial control of weeds for better crop establishment. The growth and productivity of green gram under integrated weed management was studied at the Agricultural farm of Faculty of Agricultural Sciences, Siksha ‘O’ Anusandhan, deemed to be University, Bhubaneswar, in the summer 2022. Ten treatments comprised of recommended herbicides, the stale seedbed technique, an aqueous extract of Calotropis gigantea and their combination were designed in the RBD with 3 replications. Results showed that the minimum density and biomass of weeds and maximum growth of green gram were found in twice hand weeding, which was statistically significant with the pre-emergence application of pendimethalin fb imazethapyr as post-emergence and the stale seedbed technique fb imazethapyr as post-emergence. The maximum yield (10.70 q/ha) was documented under two-hand weeding at 15 and 30 DAS, which was statistically comparable with the yield levels of sequential application of pendimethalin fb imazethapyr (10.17 q/ha) and stale seedbed technique fb imazethapyr as post-emergence (9.92 q/ha). Thus, pendimethalin at 750 g/ha at 1 DAS or stale seedbed at 15 days before sowing (DBS), followed by imazethapyr at 75 g/ha at 20 DAS, appeared to be effective in reducing the diverse weed flora significantly and achieving higher growth and yield in summer green gram.