Weed Technology最新文献

{"title":"Impact of Soil-Residual Herbicides on Industrial Hemp (Cannabis sativa L.) Phytotoxicity and Biomass Yield in West Texas","authors":"Atinderpal Singh, Rupinder Saini, Arjun Kafle, Manpreet Singh, Sukhbir Singh","doi":"10.1017/wet.2024.13","DOIUrl":"https://doi.org/10.1017/wet.2024.13","url":null,"abstract":"Industrial hemp is a multipurpose crop cultivated for fiber, seed, human food, and animal feed. Hemp legalization in Texas creates a considerable potential to increase its acreage in semi-arid conditions; however, knowledge to grow hemp optimally in Texas is limited. Best management practices, including weed control, need to be evaluated for profitable hemp production. Since little is known about the herbicide tolerance of hemp, field studies were conducted to test several soil-residual herbicides with different modes of action for phytotoxicity to two hemp cultivars, Yuma and Jinma. The experimental units were randomized three times in a blocked split-plot design with hemp cultivars in the main plots and soil-residual herbicides in the subplots. Ethalfluralin, the mixture of sulfentrazone and <jats:italic>S</jats:italic>-metolachlor, prometryn, and <jats:italic>S</jats:italic>-metolachlor, resulted in 60 to 90% and 73 to 100% weed control as compared to nontreated control in 2021 and 2022, respectively. The highest hemp germination, stand count, and plant height were observed with ethalfluralin and <jats:italic>S</jats:italic>-metolachlor herbicides; however, no significant differences were observed for hemp germination and plant height compared to nontreated control. <jats:italic>S</jats:italic>-metolachlor, ethalfluralin, fomesafen, and prometryn resulted in similar hemp biomass compared to the nontreated control. Overall, the results indicate that hemp is tolerant to ethalfluralin, prometryn, and <jats:italic>S</jats:italic>-metolachlor, and these soil-residual herbicides were effective for weed control in hemp. The mixture of bicyclopyrone and <jats:italic>S</jats:italic>-metolachlor, metribuzin and <jats:italic>S</jats:italic>-metolachlor, and mesotrione should be avoided due to significant injury to hemp plants. Future research is needed to test the efficacy of different preemergence and postemergence herbicides that can be used in industrial hemp grown under different environments, making sure the delta-9-tetrahydrocannabinol (THC) content of the hemp is below the legal content restrictions.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140002102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spray Interval, Application Order, and Plant Height Influences Control of Dicamba-Resistant Palmer amaranth","authors":"Delaney C. Foster, Thomas C. Mueller, Lawrence E. Steckel","doi":"10.1017/wet.2024.9","DOIUrl":"https://doi.org/10.1017/wet.2024.9","url":null,"abstract":"Palmer amaranth, which is resistant to glyphosate and protoporphyrinogen oxidase inhibitors, remains a threat to cotton and soybean production in Tennessee. This is partly due to the recent evolution of dicamba-resistant Palmer amaranth in West Tennessee, which further complicates weed management. Experiments were conducted in 2021 and 2022 to determine the best timing between sequential applications and in what order 2,4-D or dicamba should be used with glufosinate to control resistant Palmer amaranth. Palmer amaranth control increased when the interval between postemergence herbicide applications decreased from 21 to 7 days. At the 7-day interval in a dicamba-based system, the order of herbicides did not affect Palmer amaranth control. However, in a 2,4-D-based system, the greatest control was achieved when 2,4-D was applied first, followed by either 2,4-D or glufosinate. While weed height at the time of application had a significant effect on Palmer amaranth control with auxin herbicides, control was still unacceptable in the field at the labeled rates of dicamba or 2,4-D when applied to &lt;10 cm tall weeds (48% and 53%, respectively). Neither dicamba nor 2,4-D provided acceptable control of the Palmer amaranth populations evaluated. Sequential applications separated by 7 days provided better weed control than those separated by 21 days. Given that the better 7-day sequential treatments provided less than 90% control and resulted in more than 64,000 surviving Palmer amaranth ha<jats:sup>-1</jats:sup> suggests that relying solely on these herbicides for Palmer amaranth control is not a sustainable weed management strategy.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139981617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Confirming resistance to PPO-inhibiting herbicides applied preemergence and postemergence in a Georgia Palmer amaranth population","authors":"Taylor Randell-Singleton, Lavesta C. Hand, Jenna C. Vance, Hannah E. Wright-Smith, A. Stanley Culpepper","doi":"10.1017/wet.2024.12","DOIUrl":"https://doi.org/10.1017/wet.2024.12","url":null,"abstract":"Protoporphyrinogen oxidase- (PPO) inhibiting herbicides are used in over 40 agronomic and specialty crops across Georgia to manage weeds through residual and postemergence (POST) control. In 2017, a population of Palmer amaranth exhibiting reduced sensitivity to POST applications of PPO-inhibiting herbicides was identified by the University of Georgia. Seed were collected from the site along with a known sensitive population; distance between the samples was 200 m, increasing the likelihood of similar environmental and genetic characteristics. To quantify sensitivity for both preemergence (PRE) and POST uses, 21 greenhouse dose-response assessments were conducted from 2017 to 2022. After conducting initial rate response studies, 13 doses per herbicide were chosen for the POST experiment; field use rates of fomesafen (420 g ai ha<jats:sup>-1</jats:sup>), lactofen (219 g ai ha<jats:sup>-1</jats:sup>), acifluorfen (420 g ai ha<jats:sup>-1</jats:sup>), and trifludimoxazin (25 g ai ha<jats:sup>-1</jats:sup>) at rates ranging from 0 to 4X the field use rate for the susceptible population, and 0 to 40X for the suspect population were applied. Herbicide treatments included adjuvants and were applied to plants 8 to 10 cm in height. Relative resistance factors (RRF) were calculated for control ratings, mortality, and biomass, and ranged from 105 to 318, 36 to 1477, 215 to 316, and 9 to 49 for fomesafen, lactofen, acifluorfen, and trifludimoxazin, respectively. In the PRE experiment, herbicide applications included five to nine doses of fomesafen (1X=210 g ai ha<jats:sup>-1</jats:sup>), flumioxazin (1X=57 g ai ha<jats:sup>-1</jats:sup>), oxyfluorfen (1X=561 g ai ha<jats:sup>-1</jats:sup>), and trifludimoxazin (1X=38 g ai ha<jats:sup>-1</jats:sup>); doses ranged from 0 to 6X for the suspect population and 0 to 2X for the susceptible population. Visual control, mortality, and biomass RRF ranged from 3 to 5 for fomesafen, 21 to 31 for flumioxazin, 6 to 22 for oxyfluorfen, and 8 to 38 for trifludimoxazin. Results confirm that a Georgia Palmer amaranth population is resistant to PPO-inhibiting herbicides applied both PRE and POST.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Barnyardgrass (Echinochloa crus-galli) control and rice injury with labeled herbicides following exposure to sub-lethal concentrations of paraquat","authors":"Tameka L. Sanders, Jason A. Bond, Tom. W. Allen, Drew Gholson, L. Jason Krutz, Eric P. Webster","doi":"10.1017/wet.2024.8","DOIUrl":"https://doi.org/10.1017/wet.2024.8","url":null,"abstract":"Rice in Mississippi is often in early seedling growth stages when paraquat-based herbicide treatments are commonly applied to corn, cotton, and soybean; therefore, off-target movement onto adjacent rice fields may occur. After an off-target movement event has occurred, weed management in the rice crop is still necessary. Field studies were conducted from 2019 to 2021 in Stoneville, MS, to evaluate rice injury and barnyardgrass control with labeled herbicides after exposure to a sub-lethal paraquat concentration. Labeled herbicide treatments were recommended rates of imazethapyr, quinclorac, propanil, bispyribac-sodium, cyhalopfop, and florpyrauxifen-benzyl applied following rice exposure to a sub-lethal concentration of paraquat. Rice injury was detected 7 and 28 d after treatment (DAT) with injury ≥ 35 and 14%, respectively, following all labeled herbicides. Florpyrauxifen-benzyl and imazethapyr injured rice the greatest 28 DAT. Following paraquat exposure, barnyardgrass control was similar for all labeled herbicide treatments 7, 14, and 28 DAT except with florpyrauxifen-benzyl and no labeled herbicide (paraquat alone) 7 DAT. Across all evaluations, barnyardgrass control was at least 12% greater following paraquat exposure and labeled herbicide treatments than with no paraquat exposure. The current research demonstrates that labeled herbicides applied following exposure to a sub-lethal concentration of paraquat resulted in &lt;36% injury and provided as great as 95% control of barnyardgrass, depending on the herbicide treatment. Therefore, the labeled herbicides choice following rice exposure to a sub-lethal concentration of paraquat should be based on weed spectrum.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Control of Giant Ragweed (Ambrosia trifida) in Mesotrione-Resistant Soybean","authors":"Benjamin C. Westrich, William G. Johnson, Bryan G. Young","doi":"10.1017/wet.2024.4","DOIUrl":"https://doi.org/10.1017/wet.2024.4","url":null,"abstract":"Preemergence (PRE) applications of mesotrione, a herbicide that inhibits 4-hydroxyphenolpyruvate dioxygenase (HPPD), have recently gained regulatory approval in appropriately traited soybean varieties. Giant ragweed is an extremely competitive broadleaf weed, and biotypes resistant to acetolactate synthase inhibitors (ALS-R) can be particularly difficult to manage with soil-residual herbicides in soybean production. This study investigated control of giant ragweed from PRE applications of cloransulam (32 g ai ha<jats:sup>-1</jats:sup>), metribuzin (315 g ai ha<jats:sup>-1</jats:sup>), and <jats:italic>S</jats:italic>-metolachlor (1600 g ai ha<jats:sup>-1</jats:sup>) in a factorial design with and without mesotrione (177 g ai ha<jats:sup>-1</jats:sup>) at two different sites over two years. Treatments with mesotrione were also compared with two commercial premix products: sulfentrazone (283 g ai ha<jats:sup>-1</jats:sup>) and cloransulam (37 g ai ha<jats:sup>-1</jats:sup>), and chlorimuron (19 g ai ha<jats:sup>-1</jats:sup>), flumioxazin (69 g ai ha<jats:sup>-1</jats:sup>), and pyroxasulfone (87 g ai ha<jats:sup>-1</jats:sup>). At 42 days after planting, control and biomass reduction of giant ragweed were greater in treatments with mesotrione than any treatment without mesotrione. Giant ragweed biomass was reduced by 84% in treatments with mesotrione, while treatments without mesotrione did not reduce biomass relative to the nontreated. Following these PRE applications, sequential herbicide treatments utilizing postemergence (POST) applications of glufosinate (655 g ai ha<jats:sup>-1</jats:sup>) plus fomesafen (266 g ai ha<jats:sup>-1</jats:sup>) and <jats:italic>S</jats:italic>-metolachlor (1217 g ai ha<jats:sup>-1</jats:sup>) resulted in at least 97% control of giant ragweed at 42 days after planting, which was greater than sequential applications of glufosinate alone in 3 of 4 site-years. PRE applications of mesotrione can be an impactful addition to soybean herbicide programs designed to manage giant ragweed, with the potential to improve weed control and delay the onset of herbicide resistance by providing an additional effective herbicide site of action.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139765972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Methiozolin rate and application frequency influence goosegrass and smooth crabgrass control in turf","authors":"John M. Peppers, J. Scott McElroy, Pawel M. Orlinski, James Baird, Pawel Petelewicz, Mikerly M. Joseph, I. Alejandra Sierra-Augustinus, Marco Schiavon, Shawn D. Askew","doi":"10.1017/wet.2024.5","DOIUrl":"https://doi.org/10.1017/wet.2024.5","url":null,"abstract":"Methiozolin is labeled for goosegrass and smooth crabgrass control in golf course putting greens, but no peer-reviewed literature exists regarding this use. Greenhouse experiments were conducted evaluating goosegrass and smooth crabgrass response to increasing rates of methiozolin as affected by weed growth stage. In general, as weed growth stage increased, the methiozolin rate required to reduce weed biomass 90% (WR<jats:sub>90</jats:sub>) increased. Goosegrass was more sensitive to preemergence-applied methiozolin than smooth crabgrass, and the WR<jats:sub>90</jats:sub> was 30.4 and 118 g ai ha<jats:sup>-1</jats:sup> for goosegrass and smooth crabgrass, respectively. However, smooth crabgrass was generally more sensitive to postemergence-applied methiozolin than goosegrass. Subsequent field studies were conducted to evaluate goosegrass and smooth crabgrass control with methiozolin applied singularly or sequentially at standard preemergence timings. Results indicated methiozolin applied singularly or sequentially at the label-recommended rate (500 g ha<jats:sup>-1</jats:sup>) is not persistent enough to provide season-long control of goosegrass and smooth crabgrass. Ten field studies were conducted in Alabama, California, Florida and Virginia to evaluate frequent methiozolin application programs with the objective of providing selective, season-long goosegrass and smooth crabgrass control. Results from these studies indicate methiozolin can be safely applied to hybrid bermudagrass and creeping bentgrass putting greens despite exceeding the yearly maximum use rate for putting greens (2500 g ha<jats:sup>-1</jats:sup>) with some treatments. Methiozolin effectively controlled smooth crabgrass throughout the growing season in California and Virginia when ten biweekly applications were applied at 250 g ha<jats:sup>-1</jats:sup> or higher. In Florida, methiozolin did not acceptably (80%) control goosegrass regardless of application rate. In Virginia, methiozolin acceptably controlled goosegrass only when applied at rates and frequencies that exceeded the maximum yearly methiozolin usage rate. These data indicate that methiozolin has the potential to control smooth crabgrass preemergence when applied frequently, but does not provide acceptable goosegrass control at labeled rates.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulation-based nozzle density optimization for maximized efficacy of a machine-vision weed control system for applications in turfgrass settings","authors":"Paweł Petelewicz, Qiyu Zhou, Marco Schiavon, Gregory E. MacDonald, Arnold W. Schumann, Nathan S. Boyd","doi":"10.1017/wet.2024.7","DOIUrl":"https://doi.org/10.1017/wet.2024.7","url":null,"abstract":"Targeted spray application technologies have the capacity to drastically reduce herbicide inputs, but to be successful, the performance of both machine vision (MV) based weed detection and actuator efficiency need to be optimized. This study assessed 1) the performance of spotted spurge recognition in ‘Latitude 36’ bermudagrass turf canopy using the You Only Look Once (YOLOv3) real-time multi-object detection algorithm, and 2) the impact of various nozzle densities on model efficiency and projected herbicide reduction under simulated conditions. The YOLOv3 model was trained and validated with a dataset of 1,191 images. The simulation design consisted of 4 grid matrix regimes (3 × 3, 6 × 6, 12 × 12, and 24 × 24), which would then correspond to 3, 6, 12, and 24 non-overlapping nozzles, respectively, covering a 50-cm wide band. Simulated efficiency testing was conducted using 50 images containing predictions (labels) generated with the trained YOLO model and, by applying each of the grid matrixes to individual images. The model resulted in prediction accuracy of a <jats:italic>F</jats:italic>1 <jats:italic>Score</jats:italic> of 0.62 <jats:italic>precision</jats:italic> of 0.65 and <jats:italic>recall</jats:italic> value of 0.60. Increased nozzle density (from 3 to 12) improved actuator precision and predicted herbicide-use efficiency with a reduction in false hits ratio from <jats:sup>∼</jats:sup>30% to 5%. The area required to ensure herbicide deposition to all spotted spurge detected within images was reduced to 18% resulting in <jats:sup>∼</jats:sup>80% herbicide savings compared to broadcast application. Slightly greater precision was predicted with 24 nozzles, but not statistically different from the 12-nozzle scenario. Using this turf/weed model as a basis, optimal actuator efficacy and herbicide savings would occur by increasing nozzle density from one to 12 nozzles with the context of a single band.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139766219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Salvage Treatments for Barnyardgrass (Echinochloa crus-galli) Control in Rice Following Simulated Failed Herbicide Application","authors":"Hunter D. Bowman, Jason A. Bond, Thomas W. Allen, Daniel B. Reynolds, Taghi Bararpour, Darrin M. Dodds, Thomas W. Eubank","doi":"10.1017/wet.2024.3","DOIUrl":"https://doi.org/10.1017/wet.2024.3","url":null,"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 (POST) rice herbicides. In the first field study, florpyrauxifen-benzyl was applied at 0 and 15 g ai ha<jats:sup>-1</jats:sup> 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 POST 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<jats:sup>-1</jats:sup>. 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<jats:sup>-1</jats:sup> 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. While 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.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139657737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Emergence Timing of Smallflower Umbrella Sedge (Cyperus difformis), Barnyardgrass (Echinochloa crus-galli), and Bearded Sprangletop (Leptochloa fusca spp. fascicularis) in California Water-Seeded Rice","authors":"Katie E. Driver, Aaron Becerra-Alvarez, Mohsen B. Mesgaran, Kassim Al-Khatib","doi":"10.1017/wet.2024.2","DOIUrl":"https://doi.org/10.1017/wet.2024.2","url":null,"abstract":"Late-season weed emergence in California rice fields complicates decisions concerning the timing of control measures. The objective of this study was to predict the emergence of three problematic weed species in rice using thermal time models. Smallflower umbrella sedge, barnyardgrass, and bearded sprangletop seedlings were counted and removed daily at three locations across the Sacramento Valley rice-growing region in 2018. The accumulation of thermal time (growing degree day, GDD) commenced with the initial flooding of the fields at each location, utilizing the specific base temperatures corresponding to each species. The pattern of emergence as a function of GDD was modeled with a Weibull function. Root-mean-square values for comparing actual and model-predicted cumulative emergence values were 6 to 23%. Cumulative percent emergence initially increased rapidly for smallflower umbrella sedge and reached 90% emergence with accumulation of 13 GDD. Barnyardgrass emerged after smallflower umbrella sedge and reached 90% emergence with an accumulation of 124 GDD. Bearded sprangletop had a delay of 64 GDD compared to barnyardgrass to reach first emergence and reached 90% emergence at 215 GDD. The period of weed emergence at all field sites differed across the three species and led to a continuous spectrum of weed emergence over time. This study characterized the emergence of three economically important rice weeds and provided useful information for the timing of weed management. Typical herbicide applications on the day of seeding may have less efficacy on the late-emerging weeds, causing reduced weed control. Delaying herbicide applications, overlay of residual herbicides, or use of herbicides with longer residual activity are suggested to control late-emerging weeds.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139581210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Weed communities after decades of mineral fertilization and tillage treatments in a corn-soybean rotation","authors":"Marie-Josée Simard, Noura Ziadi","doi":"10.1017/wet.2024.1","DOIUrl":"https://doi.org/10.1017/wet.2024.1","url":null,"abstract":"Soil fertility and disturbance can potentially modify weed dynamics in a corn-soybean rotation. Knowing how added mineral fertilizers and tillage influence weed populations in the long term can provide insight into weed community shifts, which may affect future weed management requirements. The first objective of this study was to evaluate the effect of 24-25 years of nitrogen and phosphorus fertilization treatments, and tillage (moldboard vs. no tillage) on weeds (density, biomass and composition) before and after herbicide applications in 2016/corn and 2017/soybean. The second objective was to evaluate the effect of the same treatments six years after no post-emergence weed management in 2022/corn. Since the last evaluation performed in 2004, weed density, richness, and diversity increased, and more annual grasses were observed under both tillage regimes. No fertilization effect was observed on any weed variables, including composition, except for increased biomass when left to grow all season after crop planting. In managed plots, the density and biomass of annuals and perennials was generally higher in no-till, and discrepancies were highest for annual grass densities before herbicide application. Weed species richness and diversity based on counts were equivalent between tillage regimes, but total biomass was distributed between more species in no-till. Higher weed densities and concurrent weed biomass, observed in no-till, reduced crop yields in 2016/soybean only. The combination of low crop diversity and low use of residual herbicides during the trial potentially led to the observed species shifts and increased weed density.","PeriodicalId":23710,"journal":{"name":"Weed Technology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139590445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}