Early Postemergence Applications Research Articles

Noxious Weed Species Monochoria vaginalis Resistant to Synthetic Auxin and Acetolactate Synthase Inhibitor Herbicides

<em>Monochoria vaginalis</em> (Burm. f.) C. Presl is a dominant weed in paddy rice cultivation, significantly threatening productivity and farming sustainability. In Subang, Indonesia, synthetic auxin and acetolactate synthase (ALS) inhibitors are commonly used to control <em>M. vaginalis</em>. However, farmers have currently reported declining efficacy of these herbicides. Therefore, this study aimed to confirm the resistance of <em>M. vaginalis</em> to the early post-emergence application of synthetic auxin and ALS inhibitors. Plant bioassays were conducted using the pot test method to determine resistance level. Herbicides were applied 2 weeks after planting <em>M. vaginalis</em> at 0.25, 0.5, 1.0, 2.0, 4.0, and 8.0 times the recommended dose, and untreated plants as control. Herbicides tested were 2,4-D, bensulfuron-methyl, bispyribac sodium, penoxulam, and sulfentrazone. The results obtained based on resistance index values (RI) showed that <em>M. vaginalis</em> populations from Kediri and Gandasari, Subang, had moderately to high resistance to 2,4-D (RI: 8.15 and 13.0) and bensulfuron-methyl<em> </em>(RI: 205.61 and 21.80). Weed was moderately resistant to bispyribac sodium<em> </em>(RI of Kediri biotype: 8.79) and had low to moderate resistance to penoxulam herbicides (RI: 8.94 and 3.56). In contrast, <em>M. vaginalis-</em>resistant biotypes remained susceptible to sulfentrazone (protoporphyrinogen oxidase/PPO inhibitors) herbicide. A significant increase in GR50 was observed between 28 and 56 days after herbicide application, signifying enhanced regrowth. The resistance of <em>M. vaginalis</em> to synthetic auxin and ALS inhibitors presents the need for farmers to consider alternative herbicides, such as PPO inhibitors, to prevent the development of resistant weeds.

Evaluation of New Generation Herbicide-based Weed Management Strategies on Direct Sown Rice Production in Cauvery Deltaic Zone

Field assay was conducted during “Navarai” season, 2019 at Chidambaram region of cauvery delta to find out the influence of new generation herbicide based weed management in direct sown rice production. The Experiment was laid out in randomized block design with three replications using rice cultivar CO-51. The treatments includes T1- Un-weeded check, T2- Twice hand weeding at 15 and 30 DAS T3- Pre-emergence application of pyrazosulfuron-ethyl 10% WP at 200g ha-1 at 7 DAS + one Hand weeding at 30 DAS T4- Pre-emergence application of metsulfuran-methyl 10% + chlorimuron-methyl 10% WP at 20g ha-1 at 7 DAS + one Hand weeding at 30 DAS T5-Pre-emergence application of Pretilachlor 50% EC at 1250 ml ha-1 at 7 DAS + one Hand weeding at 30 DAS T6- Early post-emergence application of pretilachlor 6% + pyrazosulfuran-ethyl 0.15% G at 615g ha-1 at 15 DAS. T7- Early post-emergence application of bispyribac-sodium 10% SC at 300 ml ha-1 15 DAS T8- Early post-emergence application of pretilachlor 6% + pyrazosulfuran-ethyl 0.15% G at 615g ha-1 at 15 DAS + one Hand weeding at 30 DAS T9- Early post-emergence application of bispyribac-sodium 10% SC at 300 ml ha-1 at 15 DAS+ one Hand weeding at 30 DAS. On analysing the experimental results, it is revealed that all the imputed treatments has affected weed flora, crop growth, yield attributes and economics of direct sown rice cultivation. Furthermore, application of bispyribac-sodium 10% SC at 300 ml ha-1 at 15 DAS + one hand weeding at 30 DAS provided superior results amid all the treatments. The absence of weed management practices (i.e) T1- Un-weeded check has negatively affected the crop production to a greater extent by registering poor crop growth and yield parameters.

Weed infestation and its biodiversity under the influence of different herbicide variants application in maize cultivation

CThe main objective of Integrated Pest Management is to minimize the negative impact of pesticide use on the environment. For this purpose, technologies are developed that involve reducing doses of herbicides whose efficacy can be enhanced by adding adjuvants. This field study aimed to determine the weed control efficacy of herbicide applied at reduced doses in relation to full dose at different growth stages of maize. In the experiment, pre-emergence herbicide was applied at stage BBCH 00, while a post-emergence herbicide was at the 3, 6, or 8 leaves of maize. The herbicides were applied at doses reduced to 60% or 80% with adjuvants or at a full dose. The study has shown that pre-emergence or early post-emergence (in BBCH 13) application of the herbicide had the most beneficial effect on reducing the number and biomass of weeds in maize. The use of the doses reduced by 20% with the addition of adjuvant gave the same weed-killing effect as a 100% dose.

Bio-efficacy of Herbicides on Weed Density, Weed Control Efficiency, Productivity and Groundnut Quality in Coastal Zone of Karnataka under Rice-Groundnut System

A field experiment was conducted at Agricultural Research Station, Kumta, Uttara Kannada district during the rabi-summer season of 2016-17 to investigate the Bio-efficacy of herbicides on weed density, weed control efficiency, productivity and groundnut quality in coastal zone of Karnataka under rice-groundnut system. The experiment followed a RBD with nine treatments out of which six treatments involved the pre-emergence application of herbicides followed by either hand weeding or early post-emergence application, along with control treatments. The results indicated that the pre-emergence application of pendimethalin 30% E.C. (1.5 kg ha-1), followed by one hand weeding at 25 days after sowing (DAS), resulted in significantly reduced total weed density and weed dry matter. This treatment also demonstrated higher weed control efficiency and lower weed index. Moreover, it led to increased pod yield, kernel yield and improved quality of groundnut compared to other treatments.

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.

Effect of Weed Management Practices on Growth, Yield Attributes and Yield of Clusterbean [Cyamopsis tetragonoloba (L.) Taub

The growth, yield attributes and yield of clusterbean were influenced by various weed management treatments. The objective of the current study was to evaluate the impact of different weed management practices on growth, yield attributes and overall yield. An agronomic investigation was conducted at the Agricultural Research Station, Mandor, affiliated with the Agriculture University, Jodhpur, Rajasthan, during the Kharif season of 2018. The experimental design utilized a randomized block design (RBD) with three replications. The experiment encompassed ten treatments: W1 - weedy check, W2 - weed-free, W3 - pendimethalin at 750 g/ha (pre-emergence), W4 - imazethapyr at 40 g/ha (early post-emergence), W5 - pendimethalin + imazethapyr at 750 g/ha (pre-emergence), W6 - imazethapyr + imazamox at 50 g/ha (early post-emergence), W7 - pendimethalin at 750 g/ha (pre-emergence) + 1 hand weeding (25 days after sowing), W8 - imazethapyr at 40 g/ha (early post-emergence) + 1 hand weeding (35 days after sowing), W9 - pendimethalin + imazethapyr at 750 g/ha (pre-emergence) + 1 hand weeding (25 days after sowing), and W10 - imazethapyr + imazamox at 50 g/ha (early post-emergence) + 1 hand weeding (35 days after sowing). The early post-emergence application of imazethapyr + imazamox at 50 g/ha along with one hand weeding at 35 days after sowing resulted in significantly enhanced growth, yield attributes and overall yield. This treatment exhibited higher values for parameters such as dry matter per plant (g), plant height (cm), number of branches per plant, number of pods per plant, number of seeds per pod, 1000-seed weight (g), yields of both seed and stover and harvest index. Additionally, this treatment was comparable in effectiveness to the application of imazethapyr at 40 g/ha (early post-emergence) + 1 hand weeding at 35 days after sowing and the weed-free condition. The application of imazethapyr + imazamox at 50 g/ha + 1 hand weeding at 35 days after sowing emerged as a promising strategy during the Kharif season for achieving the highest yield and net monetary returns in clusterbean cultivation.

An Integrated Effect of Weed Management in Blackgram

A field experiment was conducted at Wetlands farm, Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore during summer season (March-June) of 2023, to study the effect of different weed management practices on weed flora, weed growth and yield of summer irrigated blackgram (VBN11). The field experiment was laid out in Randomized Block Design with nine treatments and three replications. Treatments comprised of power operated weeder at 15 DAS and 30 DAS with 40 × 7.5 cm and 45 × 7.5 cm plant spacing; pre-emergence application of pendimethalin 30% EC @ 1 kg ha-1 fb (followed by) power operated weeder at 20 DAS with 40 × 7.5 cm and 45 × 7.5 cm plant spacing; pre-emergence application of pendimethalin 30% EC @1 kg ha-1 fb early post emergence application of Imazethapyr @ 100 g ha-1 + Quizalofop-ethyl @ 50 g ha-1 (Tank mix) at 20 DAS with 40 × 7.5 cm plant spacing and 45 × 7.5 cm plant spacing; hand weeding at 20 DAS and 40 DAS with 30 × 10 cm plant spacing. The results revealed that among the various weed management practices, the weeds were effectively controlled by the pre-emergence application of pendimethalin 30 % EC @ 1 kg ha-1fb power weeder at 20 DAS with 40 × 7.5 cm plant spacing with significantly lower weed density, higher Weed Control Efficiency and higher grain yield (881 kg ha-1).

Influence of Weed Management Practices on Growth and Yield of Aerobic Rice

The present field experiment was conducted to evaluate the effects of different chemical and non-chemical weed management practices on aerobic rice. The experiment was carried out at the Wetlands Farm of the Department of Farm Management, Tamil Nadu Agricultural University, India. Pre emergence (PE) application of pendimethalin (1.0 kg ha-1), EPOE of bispyribac sodium (25 g ha-1) and EPOE of chlorimuron ethyl + metsulfuron methyl (4 g ha-1) were the chemical weed management practices. Daincha intercropping (1:1) fb spreading on 30DAS, Cowpea intercropping (1:1) fb spreading on 30DAS, Coir pith mulching (5 tons ha-1) on 3 DAS, Shredded coconut waste mulching (5 tons ha-1) on 3 DAS along with the combination of mechanical and hand weeding were the non chemical weed management practices. Pre emergence (PE) application of pendimethalin (1.0 kg ha-1) on 3 DAS fb Early post emergence (EPOE) application of bispyribac sodium (25 g ha-1) on 20 DAS recorded significantly higher growth and yield attributes. Sequential application of pendimethalin and bispyribac sodium recorded 4128 kg ha-1 grain yield which was nearly 60 per cent increased over the weedy check. Coir pith mulching @ 5 tons ha-1 on 3 DAS recorded significantly lower grain yield (1840 kg ha-1) over the rest of the treatments.

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

Effect of Tembotrione on Weed Growth and Productivity of Kharif Maize (Zea mays L.)

A field experiment was conducted in maize (Zea mays L.) during both kharif (June–September, 2014 and 2015) seasons in a randomized block design with nine treatments, including the herbicide tembotrione as early post-emergence at 80, 100 and 120 g ha-1 both as sole and in combination with atrazine at 500 g ha-1, atrazine at 1000 g ha-1, hand-weeding twice at 25 and 40 DAS and unweeded control with three replications. The experimental field was heavily infested with Ludwigia parviflora (Jacq.) Raven, Cynodon dactylon (L.) Pers., Cyperus rotundus (L.) and Fimbristylis miliacea (L.) Vahl. The yield of maize was reduced by around 48% due to weed infestation. From the experiment, it was found that combined application of tembotrione and atrazine was much more effective than sole application of herbicide at any of the levels that were evaluated. Tembotrione at a rate of 80–100 g ha-1+stefesmero surfactant at 733 g ha-1+atrazine at 500 g ha-1 recorded the lowest weed density, weed biomass and weed index; highest values of growth and yield parameters as well as the yield of maize. Therefore, early post–emergence application of tembotrione at 80–100 g ha-1+stefesmero surfactant at 733 g ha-1+atrazine 500 g ha–1 appeared to be the most effective weed management approach for higher weed control efficiency, yield, gross and net return of kharif maize in lateritic soil of West Bengal.

HPPD-resistant cotton response and weed management systems using isoxaflutole

AbstractThe southern United States produces 90% of the nation’s cotton, and the Texas High Plains is the largest contiguous cotton producing region. Since 2011, glyphosate-resistant Palmer amaranth has complicated cotton production, and alternatives to glyphosate are needed. Integrating soil residual herbicides into a weed management program is a crucial step to control glyphosate resistant weeds before emergence. The recent development of p-hydroxyphenylpyruvate dioxygenase (HPPD)-resistant cotton by BASF Corporation may allow growers to use isoxaflutole in future weed management programs. In 2019 and 2020, field experiments were conducted in New Deal, Lubbock, and Halfway, Texas, to evaluate HPPD-resistant cotton response to isoxaflutole applied preemergence (PRE) or early postemergence (EPOST) and to determine the efficacy of isoxaflutole when used as part of a season-long weed management program. At the New Deal location, cotton response was observed following the EPOST application, but it never exceeded 10%. Cotton response was greatest following the PRE application in Lubbock in 2019 but did not exceed 14%. In 2020 in Lubbock, cotton was replanted due to severe weather. There was <1% cotton response following the PRE application, and maximum cotton response observed was 9% following EPOST and mid-postemergence (MPOST) applications. Cotton lint yields were not different from those of the nontreated, weed-free control at either location. In non-crop weed control studies in Halfway, all treatments controlled Palmer amaranth ≥94% 21 d after the EPOST application. Twenty-one days after the MPOST treatment, systems with isoxaflutole applied EPOST controlled Palmer amaranth by 88% to 93%, while systems with isoxaflutole PRE controlled Palmer amaranth by 94% to 98%. End-of-season Palmer amaranth control was lowest in the system without isoxaflutole (88%) and when isoxaflutole was used EPOST (88% to 91%). These studies suggest that the use of isoxaflutole in cotton weed management systems may improve season-long control of several troublesome weeds with no adverse effects on cotton yield and quality.

Weed seed bank and weed population as influenced by weed management practices in rice var Co 54

Weed seed bank in soil serves as the reservoir of weed seeds which emerge whenever conditions become conducive and affects crop growth. In the present study, a field experiment was performed at Agricultural College and Research Institute, Tamil Nadu Agricultural University, Madurai, India, during Kharif 2021 and Rabi 2022 to determine weed seed bank present in soil by direct seed extraction using the sieving method at discrete depths of 0-5 cm, 5-10 cm and 10-15 cm after rice harvest with reference to different weed management practices imposed and its effect on weed population in succeeding crop. The average proportion of weeds that emerged in the field ranged from 9 to 38 % of the total weed seed bank. Weed management practices followed during the preceding crop greatly influenced weed seed germination. The higher weed seed reserve (1384 m-2) and consequent weed population (528 no’s m-2) were found at a depth of 0-5 cm in unweeded plots. The lower weed seed density (536 m-2) and weed population (94 no’s m-2) were found in pre emergence application of Pyrazosulfuron + Pretilachlor and early post emergence application of Bispyripac sodium. The results from the present study confirmed that herbicide treatment considerably minimized the weed seed density and population, which will assist in predicting weed infestation and appropriate timing of weed control.

Effect of new generation herbicides on mixed weed flora and yield of direct seeded rice (Oryza sativa L.)

A field experiment was conducted during the “Navarai” season of 2019 and 2020 at Experimental Farm of the Department of Agronomy, Annamalai University, Annamalai Nagar, to find out the effect of new generation herbicides on direct seeded rice (Oryza sativa L.). The herbicide used were pre-emergence application of pyrazosulfuron-ethyl 10% WP at 200 g ha-1, pre-emergence application of metsulfuran-methyl 10% + chlorimuron-methyl 10% WP at 20g ha-1, pre-emergence application of pretilachlor 50% EC at 1250 ml ha-1, Early post-emergence application of pretilachlor 6% + pyrazosulfuran-ethyl 0.15% G at 615g ha-1, Early post-emergence application of bispyribac-sodium at 300 ml ha-1. The experimental result revealed that the new generation herbicide has a significant influence on weed flora and yield attributes and yield of direct seeding rice. The result indicated that application of Bispyribac-sodium 10% SC at 300 ml ha-1 at 15 DAS + one Hand weeding at 30 DAS recorded the lowest weed population, weed dry matter production and higher weed control index (WCI) and yield. Then twice hand weeding at 15, and 30 DAS was next in order. The lowest weed control index and yield were recorded with un-weeded control.

Benzobicyclon for weedy rice control in quizalofop- and imidazolinone-resistant rice systems

AbstractGowan Company recently registered benzobicyclon, a WSSA Group 27 herbicide, as a postflood option in rice. It is the first 4-hydroxyphenylpyruvate dioxygenase-inhibiting herbicide commercially available in mid-southern U.S. rice production. In 2018 and 2019, field experiments were conducted across multiple sites in Arkansas to determine if the addition of benzobicyclon to quizalofop- or imidazolinone-resistant rice herbicide programs would improve weedy rice control. Across site-years, one application of quizalofop, either at the 1- or 3-leaf rice stage, followed by benzobicyclon applied postflood, provided comparable weedy rice control to two sequential applications of quizalofop, which is a standard herbicide program in quizalofop-resistant rice. Additionally, treatments containing quizalofop or quizalofop followed by benzobicyclon injured rice ≤5% at 28 d after the postflood application. Across site-years, at 28 d after the postflood application of benzobicyclon, all treatments containing a full-season herbicide program followed by benzobicyclon postflood provided comparable or improved weedy rice control when compared to two sequential early postemergence applications of imazethapyr. In both experiments, rice treated with benzobicyclon yielded comparably or better than treatments containing the standard herbicide program for each system. Findings from this research suggest that the use of benzobicyclon in quizalofop- and imidazolinone-resistant rice systems could be an additional and viable weedy rice control option for rice producers.

Growth and Productivity of Black Gram (Vigna mungo L.) as Influenced by Residual Effect of Triafamone Herbicide Applied for Transplanted Rice (Oryza sativa L.)

Background: The major area under black gram are cultivated as rice fallow crop to harness the available soil moisture and other resources without application of any inputs as that of other input intensive crops. Weeds are one of the important biotic factors which affect the growth and yield of black gram. The weeds can be effectively managed in black gram by the herbicide applied in the previous crop viz., transplanted rice. Since, the black gram has quick ground cover, hence initial weed management is very much important. In order to manage the weeds in rice fallow black gram crop evaluation of Triafamone herbicide applied to the transplanted rice crop was carried out in succeeding black gram crop in terms of the growth and yield of black gram. Methods: Field experiments were conducted during Kharif, 2019 (July to August) and Rabi 2019-20 (November to January) at Wetland farm of Tamil Nadu Agricultural University, Coimbatore to study the residual effect of herbicides applied in transplanted rice on succeeding black gram growth and productivity. The experiment was laid out in a randomized complete block design with three replications. The treatments consisted of four doses (30, 40, 50 and 100 g/ha) of new rice herbicide Triafamone 20% SC each as pre emergence and early post emergence, along with check herbicides Pretilachlor 50% EC 750 ml/ha and Pyrazosulfuron ethyl 10% WP 15 ml/ha as early post-emergence along with farmers practice (two hand weedings), weed free and weedy checks. Result: The weed flora of the experimental field consisted of weed complex including grasses, sedges and broad leaved weeds. Among the different dose of herbicides applied, Triafamone 20% SC at 100 g/ha markedly suppressed the weeds growth. There were no phytotoxic effects of herbicides on succeeding black gram. Different doses and time herbicides applied in transplanted rice did not affect the germination of succeeding black gram. Higher weed control efficiency, growth and yield component and yield of black gram were recorded with the Triafamone at 40 g/ha as pre emergence and early post emergence application.

Seedbank management through an integration of harvest-time and postharvest tactics for Italian ryegrass (Lolium perenne ssp. multiflorum) in wheat

AbstractItalian ryegrass is a major weed in winter cereals in the south-central United States. Harvest weed seed control (HWSC) tactics that aim to remove weed seed from crop fields are a potential avenue to reduce Italian ryegrass seedbank inputs. To this effect, a 4-yr, large-plot field study was conducted in College Station, Texas, and Newport, Arkansas, from 2016 to 2019. The treatments were arranged in a split-plot design. The main-plot treatments were (1) no narrow-windrow burning (a HWSC strategy) + disk tillage immediately after harvest, (2) HWSC + disk tillage immediately after harvest, and (3) HWSC + disk tillage 1 mo after harvest. The subplot treatments were (1) pendimethalin (1,065 g ai ha−1; Prowl H2O®) as a delayed preemergence application (herbicide program #1), and (2) a premix of flufenacet (305 g ai ha−1) + metribuzin (76 g ai ha−1; Axiom®) mixed with pyroxasulfone (89 g ai ha−1; Zidua® WG) as an early postemergence application followed by pinoxaden (59 g ai ha−1; Axial® XL) in spring (herbicide program #2). After 4 yr, HWSC alone was significantly better than no HWSC. Herbicide program #2 was superior to herbicide program #1. Herbicide program #2 combined with HWSC was the most effective treatment. The combination of herbicide program #1 and standard harvest practice (no HWSC; check) led to an increase in fall Italian ryegrass densities from 4 plants m−2 in 2017 to 58 plants m−2 in 2019 at College Station. At wheat harvest, Italian ryegrass densities were 58 and 59 shoots m−2 in check plots at College Station and Newport, respectively, whereas the densities were near zero in plots with herbicide program #2 and HWSC at both locations. These results will be useful for developing an improved Italian ryegrass management strategy in this region.

HPPD-resistant cotton response to isoxaflutole applied preemergence and postemergence

AbstractStudies were conducted in 2019 and 2020 in Lewiston, NC, to determine the crop response of 4-hydroxyphenylpyrivate dioxygenase (HPPD)-resistant cotton to isoxaflutole (IFT) and other cotton herbicides as part of a cotton weed management program that included herbicides applied preemergence, early postemergence (EPOST), and mid-postemergence (MPOST). IFT was applied PRE at 105 g ha−1 alone and in various combinations with acetochlor, diuron, fluometuron, fluridone, fomesafen, pendimethalin, and pyrithiobac. EPOST treatments included IFT at 53 or 105 g ha−1 alone or in combination with glyphosate or glufosinate, or dimethenamid-P + glufosinate. Glyphosate + glufosinate was applied MPOST to all treatments except the nontreated control. Cotton injury from IFT applied PRE was minimal (0% to 3%). Injury following EPOST application of dimethenamid-P + glufosinate ranged from 3% to 5% and 6% to 9% in 2019 and 2020, respectively. In both years, injury from IFT applied PRE followed by IFT applied EPOST never exceeded injury from IFT applied PRE followed by dimethenamid-P + glufosinate. Isoxaflutole applied PRE followed by IFT applied EPOST at 105 g ha−1 resulted in 0% to 2% cotton injury, indicating that IFT can be applied either PRE or EPOST with minimal risk to cotton. Late-season cotton height and cotton lint yield were not affected by any herbicide treatment. The experimental HPPD-resistant cotton cultivar was minimally injured by IFT applied PRE and EPOST, it tolerated standard cotton herbicides, and yield loss was not observed. Given these results, HPPD-resistant cotton and IFT may be integrated into cotton weed management systems with minimal risk for cotton injury and provide an additional effective mechanism of action for managing troublesome weeds in cotton.

Efficacy of new generation herbicides on weeds in direct seeded rice (Oryza sativa L.)

A field study was conducted during Kuruvai season of 2020 to evaluate the efficacy of new generation herbicides at Pattathikadu village, Karambakudi Taluk, Pudukkottai district, Tamil Nadu. Eleven treatments were evaluated in RBD design and replicated thrice. Early post emergence application of bispyribac sodium 10 % SC @ 200 ml ha-1 on 15 DAS fb hand weeding on 40 DAS suppressed both weed population (20.16 m-2)andweed dry matter production (33.59 kg ha-1) and recorded highest weed control index (90.70 %) at 60 DAS over unweeded check. Growth and yield attributes of ricewere significantly improved with early post emergence application of bispyribac sodium 10 % SC @ 200 ml ha-1 on 15 DAS fb hand weeding on 40 DAS. Growth attributes viz., plant height (48.80, 78.56 cm at 30, 60 DAS and 94.54 cm at harvest respectively), leaf area index at flowering stage (6.89), number of panicle m-2 (434.14), number of tillers hill-1 (26.21), dry matter production (6,946, 11,917 and 13,646 kg ha-1 at 30, 60 DAS and harvest respectively) and yield attributes viz., number of filled grain panicle-1 (94.14)and grain (6540 kg ha-1) and straw (8522 kg ha-1) yieldswere recorded under early post emergence application of bispyribac sodium 10 % SC @ 200 ml ha-1 on 15 DAS fb hand weeding on 40 DAS hence appeared to be a viable strategy for weed control in direct seeded rice.

Efficacy of new generation herbicides on weeds in direct seeded rice (Oryza sativa L.)

A field study was conducted during Kuruvai season of 2020 to evaluate the efficacy of new generation herbicides at Pattathikadu village, Karambakudi Taluk, Pudukkottai district, Tamil Nadu. Eleven treatments were evaluated in RBD design and replicated thrice. Early post emergence application of bispyribac sodium 10 % SC @ 200 ml ha-1 on 15 DAS fb hand weeding on 40 DAS suppressed both weed population (20.16 m-2)andweed dry matter production (33.59 kg ha-1) and recorded highest weed control index (90.70 %) at 60 DAS over unweeded check. Growth and yield attributes of ricewere significantly improved with early post emergence application of bispyribac sodium 10 % SC @ 200 ml ha-1 on 15 DAS fb hand weeding on 40 DAS. Growth attributes viz., plant height (48.80, 78.56 cm at 30, 60 DAS and 94.54 cm at harvest respectively), leaf area index at flowering stage (6.89), number of panicle m-2 (434.14), number of tillers hill-1 (26.21), dry matter production (6,946, 11,917 and 13,646 kg ha-1 at 30, 60 DAS and harvest respectively) and yield attributes viz., number of filled grain panicle-1 (94.14)and grain (6540 kg ha-1) and straw (8522 kg ha-1) yieldswere recorded under early post emergence application of bispyribac sodium 10 % SC @ 200 ml ha-1 on 15 DAS fb hand weeding on 40 DAS hence appeared to be a viable strategy for weed control in direct seeded rice.

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.