Rice Herbicide Research Articles

Minimizing Risks of Off-target Movement of Florpyrauxifen-benzyl by Coating onto Urea

ABSTRACT Commercialization of florpyrauxifen-benzyl as Loyant® in 2018 as a synthetic auxin herbicide in rice was followed by soybean injury due to off-target movement of spray applications in the mid-southern United States. Concerns surrounding off-target movement led to the exploration of an alternative application method to help alleviate the issue. Field experiments were conducted in 2020 and 2021 to explore the likelihood of a reduction in soybean injury following applications of florpyrauxifen-benzyl coated on urea in narrow- and wide-row soybean systems and to determine the likelihood of volatilization from this novel application method. Florpyrauxifen-benzyl spray-applied at 0.18 g ai ha-1 caused greater than 60% injury, while coating the herbicide on urea at 5.63 g ai ha-1 never exceeded 30% injury in narrow-row soybean. Similarly, florpyrauxifen-benzyl spray-applied at 0.18 g ai ha-1 caused greater than 50% injury while coating the herbicide on urea at 5.63 g ai ha-1 never exceeded 30% injury in wide-row soybean. As soybean injury increased, relative yield decreased in both narrow- and wide-row soybean. Spray-applied florpyrauxifen-benzyl decreased relative soybean groundcover, yield components, and soybean survival rate as the herbicide rate increased, whereas coating the herbicide on urea resulted in little to no decrease in both narrow- and wide-row soybean assessments. No negative impacts on relative yield and yield components of soybean from florpyrauxifen-benzyl coated on urea indicates that even though visible injury may persist, there is a low likelihood of any yield losses associated with the herbicide exposure using this application method. Additionally, coating the florpyrauxifen-benzyl on urea did not increase the likelihood of volatilization under any of the evaluated soil moisture conditions. Overall, applying florpyrauxifen-benzyl coated on urea is likely to be a safer application method and can reduce soybean injury compared to spray applying the herbicide when favorable off-target movement conditions exist.

Grapevine, peach, and plum response to simulated florpyrauxifen-benzyl drift

Abstract Off-target movement of rice herbicides is a concern in California, where sensitive crops are often grown nearby. Florpyrauxifen-benzyl and triclopyr are auxin-mimics commonly used in rice systems. To steward florpyrauxifen-benzyl around the time of its initial registration in the state, research was conducted to compare the onset of foliar symptoms from simulated florpyrauxifen-benzyl and triclopyr drift onto grapevine, peach, and plum. The rates were 1/200X, 1/100X, 1/33X, and 1/10X of the 29.4 g ai ha–1 florpyrauxifen-benzyl and 1/200X, 1/100X, and 1/33X of the 420.3 g ae ha–1 triclopyr rice use rates. Herbicides were applied on one side of one- to two-year-old peach and plum trees and one side of established grapevines in 2020 and 2021. The general symptoms for florpyrauxifen-benzyl and triclopyr were similar and included chlorosis, leaf curling, leaf distortion, leaf malformation, leaf crinkling, necrosis, and twisting on leaves. The symptoms from herbicides were observed on both sides of the grapevine canopy, whereas florpyrauxifen-benzyl symptoms on peach and plum were mostly observed on the treated side of the tree. Florpyrauxifen-benzyl and triclopyr symptoms were observed three days-after-treatment (DAT) for grapevines and seven DAT for peach and plum. In all crops, most symptoms persisted through 42 DAT. Some grape clusters showed deformation and dropping of berries. All treated crops gradually recovered during the season regardless of application rates. Because symptoms were relatively minor in peach and plum, this research suggested that application precautions that reduce off-site drift are likely to minimize the occurrence of significant injury. However, grapevines were more sensitive and showed injury symptoms up to 71% at 14 DAT with a 1/10X florpyrauxifen-benzyl simulated drift rate. Therefore, extra precautions such as using drift-management agents and proper wind speed conditions at the time of florpyrauxifen-benzyl applications may be necessary if there are nearby vineyards.

Genome-wide association study reveals the genetic basis of rice resistance to three herbicides.

Crop resistance to herbicides is crucial for agricultural productivity and sustainability amidst escalating challenges of weed resistance. Uncovering herbicide resistant genes is particularly important for rice production. In this study, we tested the resistance to three commonly used herbicides: glufosinate, glyphosate and mesotrione of 421 diverse rice cultivars and employed genome-wide association studies (GWAS) to unravel the genetic underpinnings of resistance to these three herbicides in rice. We discovered that cultivated rice exhibited rich variation in resistance to the three herbicides, and the differences among subpopulations were significant. Six identified associations harboring candidate genes for resistance to these herbicides were significant. Among them, RGlu6 and RGly8 were the major QTL for resistance to glufosinate and glyphosate, respectively. The favorable alleles of RGlu6 and RGly8 were primarily present in japonica cultivars that originated from Europe, highlighting the geographic and genetic diversity of herbicide resistance and emphasizing the localized selection pressures in European rice varieties. Moreover, our findings might suggest that traditional target genes may not contain tolerant alleles in nature, and alternative mechanisms with novel loci associated with resistance may work. By mapping the genes for herbicide resistance, our results may help develop new strategies to combat the dual challenges on effective weed management and herbicide sustainability.

Assessment of florpyrauxifen-benzyl in water-seeded rice systems as affected by application timing

Florpyrauxifen-benzyl (FPB) is a novel auxin mimic rice herbicide used to control selected grasses, sedges, and broadleaves. Field experiments were conducted in 2020–2022 to 1) characterize the effects of FPB on rice crop safety and weed control when applied alone or in a mixture, 2) determine the FPB application timing to optimize smallflower umbrella sedge (SMF) control, and 3) evaluate the effect of late season application on rice flower sterility. In the first study, FPB was applied alone at 15, 30, and 60 g ai ha−1 and in mixture with bispyribac-sodium, penoxsulam, and propanil. FPB applied alone at 30 g ha−1 at 4–5-leaf (LF) rice stage controlled more than 80% of watergrasses, ricefield bulrush, and SMF and more than 99% of all broadleaf weeds at 28 days after treatment (DAT). The mixture treatments of FPB plus bispyribac-sodium applied at maximum use rate had the greatest grass weed control whereas, FPB plus propanil at the maximum use rate provided the greatest sedge control. In the second study, FPB at 40 g ha−1 was applied at 1-LF, 10-, 15-, 20-, and 25-cm tall SMF, where treatments controlled 95%, 86%, 89%, 87%, and 85% of SMF at 42 DAT, respectively. In the third study, FPB at 40 and 80 g ha−1 rate was applied at rice panicle initiation (PI) and 50% flowering (FL) growth stages. While the weed control was more than 90% at 42 DAT for all applications, the FL stage application caused 26% and 35% rice panicle blanking at 40 and 80 g ha−1 rate, respectively. This research suggests, the window of FPB application should be from 2-LF rice to rice PI stage to ensure crop safety and highest weed control.

Phenotypic Characteristics and Occurrence Basis of Leaf Necrotic Spots in Response of Weedy Rice to Imazethapyr.

Weedy rice is the most challenging weed species to remove in rice production. We found a novel phenotype of seedling leaves which rapidly generates necrotic spots in response to imidazolinone herbicides in weedy rice, but its influencing factors and formation basis are still unknown. In this study, we used the leaf necrotic spot-producing type of weedy rice as the material. First, leaf necrotic spots were defined as physiological and vacuole-mediated cell necrosis by microscopic examination. The imazethapyr concentration was positively correlated with the degree of necrotic spots occurring, while the action site was in accordance with necrosis using herbicide stability tests combined with fluorescence parameters. Furthermore, transcriptome analysis revealed significant differences in the gene expression of endoplasmic reticulum stress and the lipid metabolism membrane structure damage pathway during necrosis, as confirmed by transmission electron microscopy. The light-temperature test also showed that high temperature and intense light could promote the appearance of necrotic spots. These experimental results are helpful in clarifying the process and basis of imazethapyr in inducing the rapid generation of necrotic spots in rice leaves and providing new insight into understanding the mechanism of response to imidazolinone herbicides and the control of weedy rice.

Seed production potential of Echinochloa colona exposed to sublethal doses of four commonly-used rice herbicides and high-temperature stress

Seed production potential of Echinochloa colona exposed to sublethal doses of four commonly-used rice herbicides and high-temperature stress

Echinochloa spp response to preemergence and postemergence herbicides in California rice (Oryza sativa L.)

Historically, herbicides were used for Echinochloa spp control in California rice production which led to the selection of herbicide-resistant biotypes. Field surveys were conducted across the seven major rice-growing counties in 2020 and Echinochloa spp samples including barnyardgrass (Echinochloa crus-galli (L.) P.Beauv.), junglerice (Echinochloa colona (L.) Link), late watergrass (Echinochloa oryzicola (Vasinger) Vasinger) and coast cockspur (Echinochloa walteri (Pursh) Heller) were collected. Greenhouse experiments were carried out to determine their suspected resistance to common preemergence and postemergence rice herbicides used in California in Fall and Winter of 2021. A total of 62 and 63 samples were characterized for suspected resistance to four preemergence granular and three postemergence foliar-applied herbicides, respectively. When granular herbicides were evaluated, samples suspected of resistance in Winter were a subset of samples that were suspected of resistance in Fall. Results indicate >90% of Echinochloa spp samples were resistant to thiobencarb, benzobicyclon + halosulfuron and penoxsulam when combined across species and counties. Cross-resistance between benzobicyclon + halosulfuron and penoxsulam was observed in >90% of the samples when combined across species and counties. Suspected clomazone resistance was observed in <75% of the samples when combined across species and counties. Suspected resistance to cyhalofop and propanil was observed in <50% of the samples when averaged across both runs. Multiple-resistance to foliar herbicides ranged from 48-60% of the samples across species and experimental runs. These results indicate the necessity for rotating herbicides during alternate cropping seasons and emphasizing integrating non-chemical strategies for Echinochloa spp control in California rice production.

Response of conventional sunflower cultivars to drift rates of synthetic auxin herbicides.

The agrochemical industry has launched several new synthetic auxin herbicides in rice to combat increasing numbers of herbicide resistant weeds to other modes of action. Excessive or inappropriate use of these herbicides has resulted in unintended consequences near the sites of application, such as herbicide drift. This study was conducted to determine the impact of drift of quinclorac and florpyrauxifen-benzyl+penoxsulam (FBP) on the yield and yield components of two sunflower cultivars. In a growth chamber experiment, quinclorac and FBP were applied to 2-4 true leaf stages at rates ranging from 2.93 to 93.75 and from 0.51 to 16.25 g ai ha-1, respectively. Nonlinear regression analyses indicated that the cultivar Bosfora was more sensitive to quinclorac and FBP than the cultivar Tunca. In field experiments, these sunflower cultivars were treated with drift rates of quinclorac (<375 g ai ha-1) and FBP (<65 g ai ha-1) when they were at the 8-10 true leaf stage. Quinclorac and FBP drift rates resulted in up to 52-61% and 85-100% injury and 82-88% and 100% yield loss, respectively. Crop injury and yield data clearly showed that cultivar Bosfora was more sensitive to FBP and quinclorac rates than cultivar Tunca, and both cultivars were more sensitive to FBP than quinclorac. In our work, we also found that plant height reduction caused by quinclorac at early growth stages may be a valuable indicator to evaluate crop injury and yield loss.

Salvage treatments for barnyardgrass (Echinochloa crus-galli) control in rice following simulated failed herbicide application

Abstract Florpyrauxifen-benzyl was commercialized in 2018 to target barnyardgrass and aquatic or broadleaf weeds. Field studies were conducted from 2019 to 2021 in Stoneville, MS, to evaluate barnyardgrass control following a simulated failure of florpyrauxifen-benzyl or other common postemergence rice herbicides. In the first field study, florpyrauxifen-benzyl was applied at 0 and 15 g ai ha–1 to rice at the two- to three-leaf stage to simulate a failed application targeting barnyardgrass. Sequential herbicide treatments included no herbicide and full rates of imazethapyr, quinclorac, bispyribac-Na, and cyhalofop applied 7 or 14 d after florpyrauxifen-benzyl treatment. The second field study was designed to evaluate barnyardgrass control with florpyrauxifen-benzyl following simulated failure of postemergence rice herbicides. Initial herbicide treatments included no herbicide and half rates of imazethapyr, quinclorac, bispyribac-Na, and propanil. Sequential applications at 7 or 14 d after the initial herbicide treatments included florpyrauxifen-benzyl at 0 and 30 g ai ha–1. Results from the first study indicated barnyardgrass control 21 d after final treatment (DAFT) was greater with sequential treatments at 7 compared with 14 d after initial treatment (DA-I) with no initial application of florpyrauxifen-benzyl. Therefore, delaying sequential treatments until 14 d after initial florpyrauxifen-benzyl at 15 g ha–1 allowed barnyardgrass to become too large to control with other rice herbicides. Rough rice yield was reduced in plots where quinclorac application was delayed from 7 to 14 DA-I with no initial application of florpyrauxifen-benzyl. The second study suggested that florpyrauxifen-benzyl application should be delayed 14 d after a herbicide failure. Although no differences in barnyardgrass control 21 DAFT were detected whether florpyrauxifen-benzyl was applied 7 or 14 DA-I of any herbicide utilized, &gt;85% control was only achieved when florpyrauxifen-benzyl application was delayed 14 DA-I. These results demonstrate barnyardgrass control options following simulated failed applications of common rice herbicides.

Control of Echinochloa spp. and Leptochloa fascicularis with the novel dihydroorotate dehydrogenase inhibitor herbicide tetflupyrolimet in California water-seeded rice

Abstract The spread of herbicide-resistant weeds is considered a major problem for rice production in California, and there is a need for new herbicides. Tetflupyrolimet is a new herbicide with a novel dihydroorotate dehydrogenase–inhibiting site of action that has strong activity on grasses. Three field studies were conducted at the California Rice Experiment Station in Biggs, CA, in 2022 and 2023 to (1) determine control of watergrass species and bearded sprangletop with tetflupyrolimet, (2) characterize the effects of tetflupyrolimet combined with other herbicides on weed control and rice, and (3) determine the response of rice cultivars to tetflupyrolimet. In the first study, tetflupyrolimet was applied at preemergence (PRE) or at the 1- to 2-leaf stage of rice (POST) at 0.1, 0.125, or 0.15 kg ai ha−1 followed by carfentrazone. Tetflupyrolimet provided ≥99% control of watergrass species and 100% bearded sprangletop control regardless of the rate or application timing, while showing no crop injury symptoms or yield reduction. In the second study, tetflupyrolimet was applied PRE or POST at 0.1 or 0.15 kg ai ha−1 followed by herbicides labeled for use in California rice production. Tetflupyrolimet provided ≥98% control of watergrass species, which was better than the grower standard treatment, and ≥97% control of bearded sprangletop. In the third study, tetflupyrolimet was applied PRE or POST at 0.125, 0.15, 0.25, or 0.3 kg ai ha−1 followed by carfentrazone. The six California rice cultivars evaluated, ‘M-105’, ‘M-206’, ‘M-209’, ‘M-211’, ‘L-208’, and ‘CM-203’, did not show any trend of crop injury caused by tetflupyrolimet. Overall, tetflupyrolimet provided a high level of control of watergrass species and bearded sprangletop without causing visual rice injury or yield reductions, regardless of rice cultivar, when applied alone or in combination with commonly used sedge and broadleaf herbicides in California water-seeded rice.

Evaluating Injury Risk Caused by Potential Drift of Florpyrauxifen‐Benzyl or Quinclorac in Corn

Of relevance to the off‐target movement of herbicides in Arkansas is the drift of rice herbicides in the state’s agricultural landscape, where aerial application of herbicides is common, raising the prima facie question of the risk of damage to other sensitive crops. The aim of this study was to evaluate the response of corn to postemergence applications of florpyrauxifen‐benzyl or quinclorac, which were applied directly to the crop at low rates (0.78 or 1.56 to 12.5% of the normal use rate for labeled crops). This was investigated through three site‐year field experiments conducted in Fayetteville (2020 and 2021) and Tillar (2020), Arkansas. Injury and yield response varied among site‐years. No corn injury was visible at the Tillar site. At the Fayetteville site in 2020, florpyrauxifen‐benzyl rates caused an average injury of 5% and 6% 2 and 4 wk after application (WAA), respectively. The 12.5% rate in 2021 caused a greater injury (7% injury) compared to other lower rates 2 WAA and such a response departed from linearity to stochasticity 4 WAA. Compared to the nontreated control, the 6.25% rate caused nearly 20% yield reduction at the Fayetteville site in 2020, and the 12.5% rate caused a 10% yield reduction at the Tillar site. The quinclorac rate of 12.5% at the Fayetteville site in 2020 caused an average of 7% injury‐2 WAA and &lt;5% injury when averaged across the other rates, or 4 WAA. The injury was more differentiated in 2021, particularly with the 12.5% rate (&gt;20% injury) from the average injury of 5% with the other lower rates 2 WAA; the injury remained similar or slightly recovered 4 WAA. Compared to the nontreated control, quinclorac rates caused an average yield reduction of &lt;5% at the Fayetteville site in 2020, whereas the 12.5% rate caused nearly 20% and 10% yield reductions at the Fayetteville site in 2021 and at the Tillar site, respectively.

Impact of Pre and Post-emergence Herbicide Mixtures in Direct Seeded Rice (Oryza sativa L.)

Rice (Oryza sativa L.) is a major source of food for more than half of the world population especially in South and Southeast Asia and Latin America. A field experiment was conducted at Krishi Vigyan Kendra, Yamunanagar district, Haryana during Kharif season of 2022 to study the effect of pre and post-emergence herbicides combinations herbicides in direct-seeded rice under irrigated condition. The experiment was laid out in a Randomized block design with three replications. The weed management treatments were T1: Pendimethalin + pyrazosulfuron T2:Pendimethalin + pyroxasulfone, T3:Pretilachlor + pyrazosulfuron, T4: Fenoxaprop-p-ethyl with safener + ethoxysulfuron,T5: Cyhalofop-butyl + penoxsulam and metsulfuron-methyl + chlorimuron-ethyl, T6.:Triafamone + ethoxysulfuron, T7: Pendimethalin + pyrazosulfuron fb bispyribac-sodium, T8: Pendimethalin + pyroxasulfone fb bispyribac-sodium, T9:Pretilachlor + pyrazosulfuron fb bispyribac-sodium, T10:Pendimethalin fb fenoxaprop-p-ethyl + ethoxysulfuron T11: Weed free, T12:Weedy check. Among herbicides, application T10 (pendimethalin fb fenoxaprop-p-ethyl + ethoxysulfuron) and T5 (cyhalofop-butyl+ penoxsulam and metsulfuron methyl + chlorimuron ethy (pre-mix) was superior over other treatment. Application of pendimethalin fenoxaprop-p-ethyl + ethoxysulfuron reduced 58.89% grassy weed and 50 % BLWs compared to weedy check plot at 60 DAS. Assessment at 60 DAS and at harvest showed that bispyribac-sodium was effective in controlling E. colona and E. crus-galli. However, bispyribac-sodium did not control D. aegyptium and L. chinensis. Fenoxaprop significantly reduced the densities of Dactyloctenium aegyptium, L. chinensis, and Digitaria sanguinalis. Fenoxaprop tank-mix with ethoxysulfuron appeared to be synergistic for the control of E. crusgalli and E. colona, and Cyperus sp. as this tank mixture. Integration of pendimethalin fb fenoxaprop-p-ethyl+ ethoxysulfuron provided control of all type of weeds with highest grain yield (6.1 t ha-1) among different treatments which was statistically at par with weed free (6.3 t ha-1). In economics points of views, the highest B-C ratio (3.03) was obtained in cyhalofop-butyl + penoxsulam + metsulfuron methyl + chlorimuron ethy followed by pendimethalin fb fenoxaprop-p-ethyl + ethoxysulfuron (2.98).

Assessing the effect of organic amendments on the degradation of profoxydim in paddy soils: Kinetic modeling and identification of degradation products

The fate and behavior of herbicides can be altered in an unpredictable way when organic amendments are added to soil as a beneficial management tool. The objective of this work was to investigate the effect exerted by the addition of two different organic amendments (alperujo compost and biochar) to soil in the degradation of one of the most relevant new generation rice herbicides, profoxydim. In unamended soils, the degradation of profoxydim was quite fast and was governed by both chemical (DT50steril soil = from 1.52 to 9.21 days) and microbial (DT50nonsterile soil = from 0.47 to 0.53 days) processes.Alperujo- and biochar-amended soils significantly increased the persistence of the herbicide in both soils, especially in the presence of biochar, due to the high capacity absorption of this amendment, increasing DT90 from 1.92 to 3.54 days for DT90unamended to 41.02–48.41 days for DT90biochar amended. Different kinetics models applied to fit the observed dissipation datasets showed that a HS biphasic model fits well with the dissipation of profoxydim in amended and unamended soils.For the first time, five degradation products (DPs) were identified by HPLC-QTOF-MS/MS in soil and a degradation pathway was described. Main DP was generated via oxidation of the sulfur atom to give rise to the corresponding sulfoxide derivative, with this DP being more persistent than the active substance.These outcomes can be very useful for the assessment of the environmental risk associated with the use of profoxydim in rice crops and the application of organic amendments as potential measures for minimizing the risk of contamination of natural water resources.

Echinochloa crus-galli seedlings surviving florpyrauxifen-benzyl applications have a greater potential to produce resistant seeds

Abstract Florpyrauxifen-benzyl (FPB) is an important postemergence rice herbicide. This study tested the potential for seed production in an FPB-resistant barnyardgrass population. A barnyardgrass population (NL) collected from a rice field in eastern China was highly resistant to FPB with a GR50 dose (the FPB dose causing a 50% reduction in fresh weight of aboveground parts) of 50.2 g ai ha−1. No significant differences in the percentages of surviving seedlings after treatment with different doses of the herbicide were found between F1 lines collected from F0 plants surviving a 36 g ai ha−1 FPB treatment and those collected from nontreated control F0 plants. Additionally, no significant differences were found in the rate of surviving seedlings after treatment with varying doses of FPB among the F2 lines collected from F1 plants that survived varying doses of FPB. At a constant temperature of 30 C, seeds from different F1 and F2 lines showed germination percentages of 85% to 92.0% and 68.3% to 89.0%, respectively. In the absence of competition, plants from the NL population surviving 0–144 g ai ha−1 FPB showed no significant differences in plant height, dry weight of aboveground parts, effective accumulated temperature (EAT) from sowing to seed maturation, seed production per plant, or 1,000-seed weight. In the susceptible population (HJ), plants surviving 18 g ai ha−1 FPB showed no significant differences compared to the nontreated control plants of the same population for the above variables. This is the first report of FPB-resistant barnyardgrass in China. Barnyardgrass seedlings that survived FPB application showed a higher potential for accumulating in the soil seedbank and negatively affecting rice.

Behavior of different weeds of Leptochloa virgata L. against the application of ACCasa inhibitor herbicides in rice (Oryza sativa)

El objetivo fue evaluar el comportamiento de diferentes malezas de Leptochloa virgata L. frente a la aplicación de herbicidas inhibidores de ACCasa en el cultivo de arroz (Oryza sativa). Para ello, se colectaron 10 poblaciones de Leptochloa virgata L, y se confrontaron con varias dosis de los herbicidas cyhalophop-butil y fenoxaprop-p-etil. Las poblaciones 1 y 10 que correspondieron a las localidades de Samborondón y Cristóbal Colón, se confrontaron con siete dosis de los dos herbicidas en estudio las cuales fueron: 1/8x, 1/4x, 1/2x, 1x, 2x, 4x y 8x. El índice de resistencia con el herbicida cyhalophop de acuerdo a la escala del ALAM a los 7 días después de la aplicación, fue alto con las poblaciones 1, 2, 6 y 10, mientras que con fenoxaprop fueron las poblaciones 1, 2, 7 y 10 las que mostraron resistencia a este producto; sin embargo, se seleccionaron las poblaciones 1 y 10 debido a que en condiciones de campo presentan problemas de control y se compararon con una población testigo. Las poblaciones 1 y 10 mostraron resistencia tanto a los 7 como a los 14 días después de la aplicación de ambos productos. La mayor toxicidad la provocó la dosis de 8x con ambos herbicidas, al igual que sobre la altura de planta, peso de materia fresca, seca y total. La DL50 de ambos herbicidas en la población 1 fue alta (220.53 pppm i.a).

Deciphering insights into rhizospheric microbial community and soil parameters under the influence of herbicides in zero-tillage tropical rice-agroecosystem

Extensive use of chemicals like herbicides in rice and other fields to manage weeds is expected to have a lasting influence on the soil environment. Considering this rationale, we aimed to decipher the effects of herbicides, Pendimethalin and Pretilachlor, applied at 0.5 and 0.6 kg ha−1, respectively on the rhizosphere microbial community and soil characteristics in the tropical rice field, managed under zero tillage cultivation. The quantity of herbicide residues declined gradually since application up to 60 days thereafter it reached the non-detectable level. Most of the soil variables viz., microbial biomass, soil enzymes etc., exhibited slight reduction in the treated soils compared to the control. A gradual decline was observed in Mineral-N, MBC, MBN and enzyme activities. Quantitative polymerase chain reaction results showed maximal microbial abundance of bacteria, fungi and archaea at mid-flowering stage of rice crop. The 16 rRNA and ITS region targeted amplicons high throughput sequencing microbial metagenomic approach revealed total of 94, 1353, and 510 species for archaea, bacteria and fungi, respectively. The metabarcoding of core microbiota revealed that the archaea comprised of Nitrososphaera, Nitrosocosmicus, and Methanosarcina. In the bacterial core microbiome, Neobacillus, Nitrospira, Thaurea, and Microvigra were found as the predominant taxa. Fusarium, Clonostachys, Nigrospora, Mortierella, Chaetomium, etc., were found in core fungal microbiome. Overall, the study exhibited that the recommended dose of herbicides found to be detrimental to the microbial dynamics, though a negative relation between residues and soil variables was observed that might alter the microbial diversity. The outcomes offer a comprehensive understanding of how herbicides affect the microbial community in zero tillage rice soil, thus has a critical imputation for eco-friendly and sustainable rice agriculture. Further, the long-term studies will be helpful in elucidating the role of identified microbial groups in sustaining the soil fertility and crop productivity.

Integrated Control of Echinochloa oryzoides, Echinochloa crus-galli and Cyperus difformis Based on Pre-Sowing Herbicide and Some Herbicide Combinations in Rice

Cosmopolitan weeds are even constant elements where rice cultivation started just a century ago. There are few but important weed species with high adaptation in rice, which requires monoculture production systems and aquatic environment. Rotation difficulty resulted in the proliferation of highly competitive weed species strongly adapted to the aquatic environment. Constant use of herbicides with the same mechanisms of action leads to an evaluation of herbicide-resistant weed population and an increased number of herbicide-resistant populations in Türkiye. Chemical weed control and alternative integrated weed management strategies in rice production systems have significantly evolved throughout the years as well as rice herbicide traits and weed spectrum. The study was carried out in rice fields with resistance problems in two different locations, in the Black Sea and the Marmara Regions. The clamozone 480 EC, oxadiazon 200 CS, glyphosate potassium 441 g/l, glyphosate IPA 360 g/lt +carfentrazone-ethyl 5 g/l, cyhalofop-butyl 200 EC, penoxsulam 25.2 OD +bentazon-sodium 480 SL active ingredients and combinations’ efficacy were investigated on ALS and ACCase inhibitor herbicides resistant Cyperus difformis, Echinochloa oryzoides and Echinochloa crus-galli populations. At the end of the study, it was determined that including pre-sowing herbicides such as clomazone and oxadiazon in the weed control program would help control the ALS and ACCase-resistant this species. Implementing integrated weed management strategies for managing existing herbicide-resistant weeds and reducing future development of herbicide resistance is one of our most influential and economical long-term strategies.

Risk of Pesticides Mixtures in Rice to Birds and Humans in Iran.

Rice is a staple in the diet of nearly half of the world's population. As with most crops, pesticides are used as a tool to increase crop yield in rice farming. This study investigated the residues of 14 organophosphate insecticides and 2 herbicides in rice cultivated at five locations in the southwest of Iran. The pesticide residues were then used to estimate the risk that they may pose to the health of bird and human consumers. The rice samples from the five locations contained residues from 10 to 13 pesticides. Of the 16 pesticides measured, the mean concentration of 12 pesticides exceeded the maximum residue limit set by the Iranian National Standards Organization at two or more of the sampling sites. The greatest total exceedance (sum of all pesticides detected in rice) of the species sensitivity distributions constructed for birds was 0.74% and the level of concern set for the assessment was an exceedance ≥ 5%, which suggests a relatively low risk to birds. For human consumers, no single pesticide measured in rice samples posed a considerable risk. However, when considering the mixture of pesticides present in rice samples, the cumulative risk exceeded the level of concern in all samples from all sites. The margin of safety for the mixture of pesticides present in rice samples ranged from 5.8 to 29.1, with 1 being the level of concern. The results of this study indicate that efforts need to be made to mitigate the exposure of human consumers to pesticides present in rice cultivated in Iran. This study also highlights the need to collect data on pesticides residues in other crop cultivated in Iran.

Weed management in direct-seeded rice (Oryza sativa) in central India

A field experiment was conducted in a split-plot design with 3 replications at Research Farm, College of Agriculture, Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur (Madhya Pradesh), during the rainy (kharif) season of 2019, to evaluate the performance of different herbicides in direct-seeded rice (Oryza sativa L.). The experiment comprised of 2 main plots, viz. rainfed and irrigated, and 8 weed-control treatments, viz. bispyribac sodium at 25 g/ ha, fenoxaprop-p-ethyl at 60 g/ha, fenoxaprop-p-ethyl + penoxsulam at 60 + 26.7 g/ha, cyhalofop + penoxsulam at 135 + 26.7 g/ha, bispyribac sodium + metsulfuron-methyl + chlorimuron ethyl at 25 + 4 g/ha, triafamone + ethoxysulfuron at 40 + 20 g/ha, hand-weeding twice and weedy check, in subplots. The dominant weeds associated with direct-seeded rice experimental field were mainly comprised monocot, viz. jungle rice [Echinochloa colona (L.) Link] and Bermuda grass [Cynodon dactylon (L.) Pers.], sedge, viz. nutgrass [Cyperus iria (L.)], and dicot weed such as sissoo spinach [Alternanthera sessilis (L.) R. Br. ex DC.]. The results indicated that, post-emergence application of bispyribac sodium at 25 g/ha at 20 days after sowing (DAS) recorded the highest weed-control efficiency (87.75%), followed by fenoxaprop-p-ethyl + penoxsulam at 60 + 26.7 g/ha. Higher grain yield (3.09 t/ ha) was recorded with weed-free treatment which was at par with bispyribac sodium at 25 g/ha.

CRISPR-Cas9-mediated editing of the OsHPPD 3′ UTR confers enhanced resistance to HPPD-inhibiting herbicides in rice

This study reports the creation of herbicide-resistant rice lines via CRISPR-Cas9-mediated editing of the 3' UTR of OsHPPD. Resistance index calculations revealed that two resistant lines, TS8-2#-10 and TS8-8#-6, exhibited 4.8-fold and 3.7-fold greater resistance to HPPD-inhibiting herbicides compared with the wild type, YG3012.