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Herbicide resistance in crop plants is valuable for integrated weed management in agriculture. Herbicide resistant rice, in particular, is important to management of weedy rice, a close relative of cultivated rice and a noxious weed prevalent in rice fields that remains challenging to farmers worldwide. Herbicide resistant plants can be obtained through transgenic approach or by mutagenesis of regular plant and screening of mutants with elevated resistance to herbicide. In this study, we conducted ethyl methyl sulfonate mutagenesis (EMS) to elite indica cultivar Huanghuazhan (HHZ) and screened for mutants resistant to imazapic, a herbicide that can inhibit the acetolactate synthase (ALS) in plants. We obtained three mutants of OsALS gene that have not been reported previously in rice. One of the mutants, with Trp548 changed to Met (W548M), was analyzed in more details in this study. This mutation had no negative effect on the plant physiology and morphology as well as rice yield. Compared with the imidazolinone-resistant mutant S627N (Ser627 changed to Asn) that has been deployed for Clearfield rice development, W548M mutant showed high levels of resistance to a broad spectrum of five families of ALS-inhibiting herbicides, in addition to a higher level of resistance to herbicides of the imidazolinone family. The herbicide-resistance was stably inherited by crossing into other rice lines. Thus, the W548M mutation provides a valuable resource for breeding of herbicide resistant rice and weed management.

Invasive annual grasses such as cheatgrass (Bromus tectorum L.) outcompete native grasses, increase fire frequency, and impact the functionality and productivity of rangeland ecosystems. Preemergent herbicide treatments are often used to control annual grasses but may limit timely restoration options due to negative effects on concurrently planted desired seeded species. We tested the efficacy of activated carbon-based herbicide protection coatings applied to individual bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Love) seeds for protecting seedlings from injury associated with pre-emergent herbicide (imazapic) application in a laboratory environment. Emergence of coated seed averaged 57% ± 5% compared with bare seed, which had 14% ± 10% emergence with imazapic application. Seedling height for coated seed averaged 7.56 ± 0.6 cm compared with 2.26 ± 0.4 cm in uncoated bare seed in the presence of imazapic. Coated seeds produced 87% more plant biomass than uncoated seeds. Our laboratory results suggest that treating individual seeds with an activated carbon-based coating dramatically reduces negative effects of pre-emergent herbicide on desired seeded species. Field studies are needed to confirm these results in an applied restoration context.

Top-down and bottom-up factors affecting invasive populations are rarely considered simultaneously, yet their interactive responses to disturbances and management interventions can be essential to understanding invasion patterns. We evaluated post-fire responses of the exotic perennial forb Chondrilla juncea (rush skeletonweed) and its biocontrol agents to landscape factors and a post-fire combined herbicide (imazapic) and bacteria (Pseudomonas fluorescens strain MB906) treatment that targeted invasive annual grasses in a sagebrush steppe ecosystem. Biocontrol agents released against C. juncea in previous decades included Cystiphora schmidti (gall midge), Aceria chondrillae (gall mite), and Puccinia chondrillina (rust fungus). C. juncea abundance was greater in sprayed than unsprayed plots, and where soils were coarser, slopes faced southwest, solar heat loads and topographic water accumulation were greater, and cover of deep-rooted native perennials was lower. Mite infestation was greater in unsprayed plots, midge infestation was greater at higher elevations on steeper slopes, and midges were more abundant while rust was less abundant on gravelly soils. Biocontrol infestation levels varied considerably between years and could not be predicted in 2019 from 2018 infestation levels. Multiple biocontrol species were often present at the same plots but were rarely present on the same C. juncea individuals. These results suggest that spatial patterns of invasion by C. juncea are related to deep-soil water availability, warmer conditions, and alleviation of competition. Treatments designed to reduce invasive annual grasses may inadvertently release C. juncea by both reducing plant competition for soil resources and affecting biocontrol agent (mite) abundance.

Concern about the impacts of two invasive annual brome grasses (cheatgrass and Japanese brome, Bromus tectorum L. and B. japonicus Thunb. ex Murray) on the mixed-grass prairie of North America's northern Great Plains (NGP) is growing. Cheatgrass is well known west of the NGP, where replacement of fire-intolerant, native sagebrush steppe by fire-prone, exotic annual grasslands is widespread. Consequently, fire is often not considered as a tool for controlling annual bromes. This should not be the case in the NGP, where mixed-grass prairie is adapted to frequent fires. Fire's efficacy may vary with the degree of invasion, though; suppressing postfire annual brome populations or enhancing the native plant community may improve postfire annual brome control in highly invaded areas. To test this, we performed an experiment at two sites to evaluate the relative effectiveness of prescribed fire alone, fire followed by imazapic application and fire followed by native seeding across a pretreatment invasion gradient of annual brome-to-native species cover ranging from 0.05 to 2.35. Fall-prescribed fire alone greatly reduced annual bromes, but by the second yr after treatment the effect was significant only at invasion ratios 1.2 in yr 2 at the other site. Native species cover and total species richness responded positively to all treatments, but the degree of their response varied along the invasion gradient, between sites, with time since treatment and among treatments. Also, at one site, fire yielded a lagged stimulation of short-lived, exotic forbs. Seeding had little effect. Fire is an effective tool for reducing annual bromes in the NGP at lower invasion levels, but more tools are needed for long-term, effective control at highly invaded sites.

Made available in DSpace on 2021-06-25T10:23:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Universidade Federal do Paraná One of the factors that limit grain yield in soybean crops is weed competition. The objective of the present work was to evaluate the agronomic performance of an AHAS-transgene soybean cultivar (BRS 397; Cultivance®) subjected to different rates of Soyvance® (525 g kg-1 imazapyr, and 175 g kg-1 imazapic). Two field experiments were conducted in the 2015-2016 crop season in two sites with different soil and weather characteristics located in the state of Paraná, Brazil. A completely randomized block design was used, with 11 treatments consisted of different rates of Soyvance®. Phytotoxicity, chlorophyll index, first pod height, plant height, number of pods per plant, 100-seed weight, and grain yield were evaluated. The use of high rates of the herbicide decreased the final height and grain yield of soybean plants in approximately 25% in both locations, but did not affect their 100-seed weight and chlorophyll index. The use of rates of the commercial product higher than that recommended by the manufacturer (100 g ha-1) may affect the agronomic performance of AHAS-transgene soybean plants. São Paulo State University (UNESP) School of Agricultural Sciences Federal University of Paraná (UFPR) Department of Agricultural Sciences, Palotina State University of Maringá (UEM) Program of Agricultural Science, Maringá São Paulo State University (UNESP) School of Agricultural Sciences

Rangeland managers need tools to control invasive annual grasses, particularly following wildfire. We assessed responses of native and invasive/exotic grasses to the MB906 soil amendment containing live cultures of a purportedly weed-suppressive strain of the bacterium Pseudomonas fluorescens (“WSB”). MB906 was applied alone and in combination with the pre-emergent herbicide imazapic on >3000 ha across three sagebrush-steppe landscapes burned several months prior. Replicate plots of each treatment type were established and plant cover was measured in the following three years. Cover of invasive-annual grasses (“IAG”) was not responsive to MB906 when all IAG species were considered (“IAG-All”). However, MB906 led to a 54% reduction in the IAG's that were previously reported to be controlled by WSB (“IAG-Target”) in the second year following application (IAG-Target = cheatgrass, Bromus tectorum and medusahead, Taeniatherum caput-medusae; IAG-All also includes Vulpia myuros and Bromus arvensis). MB906 reduced the effectiveness of co-applied imazapic: Imazapic alone reduced IAG-All by 83% and 68% in years 1 and 2, respectively, while imazapic+MB906 reduced IAG-All by 48% and 38% in years 1 and 2, respectively, across all landscapes, and a similar response pattern was observed for IAG-Target. Perennial grass cover was unaffected by the treatments except where it increased 4-fold in response to imazapic applied at a high rate (0.140 kg a.i. ha−1) in one of the landscapes. Tank mixing MB906 and herbicide may have lessened the biological activity of the herbicide by altering the pH or mineral content of the spray solution or by direct metabolism of the herbicide by the bacteria. These results do not provide strong support for MB906 as a tool for annual grass control, though they suggest further investigation may be warranted.

Approaches and techniques for control of exotic annual grasses are a high priority in rangelands including sagebrush steppe. Strains of the soil bacterium Pseudomonas fluorescens have been proposed to be selectively pathogenic to multiple species of exotic annual grasses (“Pf,” weed-suppressive bacteria, “WSB”). However, defensible tests of the target and nontarget effects of these WSB strains in the field are needed. We evaluated the effects of D7 and MB906 strains of Pf WSB in sagebrush steppe invaded by cheatgrass (Bromus tectorum L), medusahead (Taeniatherum caput-medusae L. Nevski), and other exotic annual grasses. We evaluated the WSB strains with and without herbicides (imazapic, rimsulfuron) or discing to mix surface-spray of the WSB into deeper soils, and we replicated these tests in three ecoregions that differed in soils and climate. Over 3 yr after treatment, neither WSB strain affected cover of exotic annual grasses, perennial bunchgrasses, or the total community, either with WSB alone or in combination with herbicides or discing. WSB has received considerable attention and is being applied across large rangeland areas, but the WSB strains and methods applied here were ineffective. We recommend any future use of WSB be applied in an experimental fashion, with experimental design and measurement of responses, until its effects can be proven.

Revegetation of exotic annual grass−invaded rangelands is a primary objective of land managers following wildfires. Controlling invasive annual grasses is essential to increasing revegetation success; however, preemergent herbicides used to control annual grasses prohibit immediate seeding due to nontarget herbicide damage. Thus, seeding is often delayed 1 yr following herbicide application. This delay frequently allows for reinvasion of annual grasses, decreasing the success of revegetation efforts. Incorporating seeds into herbicide protection pods (HPPs) containing activated carbon (AC) permits concurrent high preemergent herbicide application and seeding because AC adsorbs and renders herbicides inactive. While HPPs have, largely in greenhouse studies, facilitated perennial bunchgrass emergence and early growth, their effectiveness in improving establishment of multiple species and functional groups in the field has not been assessed. Five bunchgrass species and two shrub species were seeded at two field sites with high imazapic application rates as bare seed and seed incorporated into HPPs. HPPs significantly improved establishment of sagebrush (Artemesia tridentata Nutt. Spp. wyomingensis Beetle & Young) and crested wheatgrass (Agropyron cristatum [L.] Gaertn.) over the 2-yr study. Three native perennial grass species were protected from herbicide damage by HPPs but had low establishment in both treatments. The two remaining shrub and grass species did not establish sufficiently to determine treatment effects. While establishment of native perennial bunchgrasses was low, this study demonstrates that HPPs can be used to protect seeded bunchgrasses and sagebrush from imazapic, prolonging establishment time in the absence of competition with annual grasses.

Herbicide mixtures, use of multiple sites of action, and other weed management practices are necessary to avoid cases of biotype resistance. The aim of this study was to evaluate the efficiency of imazapic/imazapyr and other herbicides in mixtures to control Digitaria insularis at burndown before soybean sowing. This field research was conducted in Umuarama, State of Parana (PR), Brazil, in the 2018/19 soybean season. The experiment was conducted in a randomized block experimental design with four replications and 11 treatments composed of the application of glyphosate, clethodim, haloxyfop, imazapic/imazapyr, glufosinate, 2,4-dichlorophenoxyacetic acid (2,4-D), dicamba, triclopyr, and saflufenacil, in mixtures. Weed control was evaluated as well as soybean injury and yield. An analysis of variance and F-test were performed, and the treatment means were compared by the Scott-Knott test. All treatments showed great control over the weed and low crop injury rate while maintaining soybean yield. The application of imazapic/imazapyr in mixtures with other herbicides was effective in controlling glyphosate-resistant D. insularis in burndown before soybean sowing and with sequential application of haloxyfop + glyphosate at V3 stage of soybean. This chemical management was also selective for soybean.

Pintoi peanut is a warm-season perennial legume that shows promise as a forage crop for the southeastern United States, however, little is known about the proper methods of weed management during establishment for this species. The objective of this study was to determine the ability of pintoi peanut to tolerate applications of PRE and POST herbicides during the year of and year after planting. The effects of herbicide treatments on percentage of visual estimates of injury and stand counts of pintoi peanut were investigated at Ona and Marianna, FL, in 2015 and 2016. All PRE herbicides did not result in significant injury or stand reduction. Pintoi peanut’s tolerance to POST herbicides was higher when plants were emerged for at least 2 wk prior to herbicide application. Stands of pintoi peanut that were planted the previous year appear to tolerate all herbicides examined in this work, except sulfosulfuron. Results of this study indicate that at the year of planting pintoi peanut is tolerant to PRE applications of pendimethalin, imazethapyr, and imazapic. Pintoi peanut appears to tolerate applications of 2,4-D, carfentrazone, imazapic and imazethapyr the year after planting at the rates utilized in this study. Future research should evaluate the effects of multiple herbicide applications and tank-mixes to obtain satisfactory weed control and selectivity in pintoi peanut swards.

Indaziflam, a PRE herbicide option for weed management on rangeland and natural areas, provides long-term control of invasive winter annual grasses (IWAGs). Because indaziflam only provides PRE control of IWAGs, POST herbicides such as glyphosate can be mixed with indaziflam to control germinated IWAG seedlings. Field trials were conducted at three sites on the Colorado Front Range to evaluate glyphosate dose required to provide adequate POST IWAG control and compare long-term downy brome (Bromus tectorum L.), Japanese brome (Bromus arvensis L.), and feral rye (Secale cereale L.) control with indaziflam and imazapic. Two of the three sites were void of desirable species, so species establishment through drill seeding was assessed, while the remnant native plant response was assessed at the third site. Herbicide applications were made March 2014 through April 2015, and two sites were drill seeded with native species 9 mo after herbicide application. Yearly visual control evaluations, biomass of all plant species, and drilled species stand counts were collected. Glyphosate at 474 g ae ha−1 reduced B. tectorum biomass to zero, while glyphosate at 631 g ae ha−1 was needed to reduce biomass to near zero at the S. cereale site. At all three sites, only indaziflam treatments had significant reductions in IWAG biomass compared with the nontreated check at 3 yr after treatment (YAT). By 3 YAT in the drill-seeded sites, cool-season grass frequency ranged from 37% to 69% within indaziflam treatments (73 and 102 g ai ha−1), while imazapic treatments ranged from 0% to 26% cool-season grass frequency. In the site with a remnant native plant community, indaziflam treatments resulted in a 3- to 4-fold increase in native grass biomass. These results indicate that the multiyear IWAG control provided by indaziflam can aid in desirable species reestablishment through drill seeding or response of the remnant plant community.

Using herbicides results in environmental impacts and it is necessary employing sustainable technologies to reduce its residues in the soil. Imazapic, used in the sugarcane cultivation, shows persistence and mobility in the environment. This study aimed to identify plant species tolerant to imazapic with the potential for phytoremediation of soils with residues of this herbicide. The tests were conducted under greenhouse conditions involving the species Urochloa decumbens, Urochloa brizantha, Urochloa ruziziensis, Mucuna pruriens, Panicum maximum, Sorghum bicolor, Crotalaria ochroleuca, Crotalaria spectabilis and Canavalia ensiformis grown in two soils: one of sandy clay loam texture and the other of sandy clay texture. In each test, five imazapic doses (0.00, 58.33, 87.50, 175.00 and 350.00 g ha-1) were applied in pre-emergence. In all tests, the treatments were in randomized blocks with four replicates each. The soil of sandy clay loam texture with low organic carbon content decreased the tolerance of the evaluated species to imazapic due to its higher bioavailability. The species Canavalia ensiformis, Mucuna pruriens and Urochloa brizantha demonstrated lower phytotoxicity and higher dry matter production in the presence of the highest imazapic doses in the soil. The tolerance from these species can be considered as an indicator of their phytoremediation potential of soils contaminated with imazapic.

O imazapic por apresentar longo efeito residual no solo pode ocasionar intoxicação visual em culturas sensíveis semeadas em rotação, além de representar riscos ecotoxicológicos em ambientes aquáticos. Diante disso, a fitorremediação é uma proposta inovadora como método alternativo para a remoção de poluentes orgânicos, sendo o sucesso da técnica dependente da seleção criteriosa de plantas com características favoráveis. O objetivo do estudo foi de identificar espécies de plantas tolerantes ao imazapic para potencial uso em programas de fitorremediação. Foram conduzidos oito experimentos em casa de vegetação climatizada com as espécies, Panicum maximum, Crotalaria juncea, Stylosanthes spp., Cajanus cajan, Dolichos lablab, Pennisetum glaucum, Mucuna aterrima, Raphanus sativus e cinco doses de imazapic (0; 58,33; 87,5; 175 e 350 g ha-1). Os tratamentos foram delineados em blocos ao acaso com quatro repetições. Aos 30 e 60 dias após a emergência das plantas foram avaliados os sintomas de intoxicação visual, altura e a massa seca das plantas, determinada ao término do experimento. As espécies M. aterrima, C. cajan e D. lablab não apresentaram sintomas visuais de fitointoxicação. M. aterrima foi a que promoveu maior produção de massa seca quando cultivada como testemunha e a exposição ao imazapic pouco afetou essa característica. Nas espécies tolerantes, a redução da altura e massa seca exigiu doses maiores, embora os resultados não tenham sido significativos para D. lablab e C. cajan. Entre essas espécies, M. aterrima se destacou pela alta produção de biomassa, sendo promissora na fitorremediação de sítios com resíduos do imazapic.

Herbicide contamination of nearshore tropical marine ecosystems is widespread and persistent; however, risks posed by most ‘alternative’ herbicides to tropical marine microalgae remain poorly understood. Experimental exposures of the important but understudied microalgae Rhodomonas salina to seven individual Photosystem II (PSII) inhibitor herbicides (diuron, metribuzin, hexazinone, tebuthiuron, bromacil, simazine, propazine) led to inhibition of effective quantum yield (ΔF/Fm′) and subsequent reductions in specific growth rates (SGR). The concentrations which reduced ΔF/Fm′ by 50% (EC50) ranged from 1.71-59.2 µg L−1, while the EC50s for SGR were 4-times higher, ranging from 6.27-188 µg L−1. Inhibition of ΔF/Fm′ indicated reduced photosynthetic capacity, and this correlated linearly with reduced SGR (R2 = 0.89), supporting the application of ∆F/Fm’ inhibition as a robust and sensitive indicator of sub-lethal toxicity of PSII inhibitors for this microalga. The three non-PSII inhibitor herbicides (imazapic, haloxyfop and 2,4-Dichlorophenoxyacetic acid (2,4-D)) caused low or no toxic responses to the function of the PSII or growth at the highest concentrations tested suggesting these herbicides pose little risk to R. salina. This study highlights the suitability of including R. salina in future species sensitivity distributions (SSDs) to support water quality guideline development for the management of herbicide contamination in tropical marine ecosystems.

Japanese stiltgrass is regarded as one of the most troublesome invasive species in the United States. It is commonly found invading forested areas; however, more recently it has been noted to be invading golf course roughs and out-of-play areas. The purpose of this study was to evaluate POST herbicide control of Japanese stiltgrass in golf course and highly maintained turfgrass facilities. None of the treatments provided >80% Japanese stiltgrass control 2 wk after treatment (WAT). At 4 WAT >80% Japanese stiltgrass control was observed with MSMA, MSMA + metribuzin, amicarbazone, and sethoxydim, whereas metsulfuron, pinoxaden, and imazapic provided minimum control. By 8 WAT, MSMA, MSMA + metribuzin, amicarbazone, and sethoxydim provided >98% control, whereas quinclorac, metsulfuron, pinoxaden, and imazapic provided no visible control. Thiencarbazone-methyl + foramsulfuron + halosulfuron-methyl, and sulfentrazone provided limited (≤60%) control. This study indicates that POST control of Japanese stiltgrass can be achieved with MSMA, MSMA + metribuzin, amicarbazone, and sethoxydim. Future research should include long-term control over multiple growing seasons, repeat applications of herbicides, and evaluation of herbicides in combination for increased and longer-term Japanese stiltgrass control.

The phytostimulation is a phytoremediation technique that can be used to remediate area contaminated with herbicides. It is necessary to select plants with high capacity to stimulate soil microbial activity. The present work aimed at evaluating seven plant species regarding their ability to phytostimulate soil and enhance the degradation of the herbicides imazethapyr, imazapic and imazapyr in a lowland soil. An Alfisol Albaqualf was cultivated with the following species

Giant miscanthus has the potential to move beyond cultivated fields and invade noncrop areas, but this can be overshadowed by aesthetic appeal and monetary value as a biofuel crop. Most research on giant miscanthus has focused on herbicide tolerance for establishment and production rather than terminating an existing stand. This study was conducted to evaluate herbicide options for control or terminating a stand of giant miscanthus. In 2013 and 2014, field experiments were conducted on established stands of the giant miscanthus cultivars ‘Nagara' and ‘Freedom.’ Herbicides evaluated in both years included glyphosate, hexazinone, imazapic, imazapyr, clethodim, fluazifop, and glyphosate plus fluazifop. All treatments were applied in summer (June or July) and September. For both years, biomass reduction ranged from 85% to 100% when glyphosate was applied in June or July at 4.5 or 7.3 kg ae ha–1. No other treatment applied at this timing provided more than 50% giant miscanthus biomass reduction 1 yr after application. September applications of glyphosate were not consistent: treatments in 2013 reduced biomass by 40% or less, whereas in 2014, at all rates provided at least 78% biomass reduction. Glyphosate applied in June or July was the only treatment that provided effective and consistent control of giant miscanthus 1 yr after treatment.Nomenclature: Clethodim; fluazifop; glyphosate; hexazinone; imazapic; imazapyr; giant miscanthus, Miscanthus x giganteus J.M. Greef & Deuter ex. Hodkinson & Renvoize [sacchariflorus × sinensis]

Cover crops can provide many benefits to peanut and cotton crops planted in rotation including suppressing weeds, conserving soil moisture after termination, increasing soil organic matter, and reducing soil erosion. However, herbicide carryover can affect cover crop establishment. The objective of this study was to investigate the responses of 6 cover crops (daikon radish, cereal rye, oat, crimson clover, winter wheat, and common vetch) to 12 soil residual herbicides. A multiyear (2016–2018), multilocation study was conducted in Macon and Henry counties, Alabama. Herbicide treatments included S-metolachlor, acetochlor, pyroxasulfone, diclosulam, imazapic, chlorimuron-ethyl, bentazon plus acifluorfen, pyrithiobac-sodium, trifloxysulfuron-sodium, diuron, prometryn, and flumioxazin, each applied at 10% of the full-labeled rate. At 42 to 52 and 145 to 149 d after planting (DAP), cover crop plant heights and stand counts were evaluated, as was biomass at 145 to 149 DAP. Treatments varied from year to year but not locations. In 2016, significant stand reductions (P ≤ 0.10) of 36% to 43% in rye and 44% to 75% in wheat were observed at 48 to 52 DAP for S-metolachlor, acetochlor, pyroxasulfone, imazapic, and bentazon plus acifluorfen compared with nontreated plants. Vetch had stand reductions ranging from 14% to 80% for all treatments 50 DAP except for plants treated with prometryn. S-metolachlor, pyroxasulfone, and acetochlor reduced stands of rye, wheat, and vetch more than any other herbicides. In 2017, at 147 to 149 DAP, clover stands were reduced by 29% with diclosulam and by 38% with trifloxysulfuron-sodium. Similarly, radish stands were reduced by 64% with diclosulam treatment. No significant biomass reductions were observed for any cover crop species either year. Oat showed the most tolerance with no treatments reducing any growth parameters either year. Although initial injury and stunting may occur, biomass at termination of cover crops were not affected by herbicide residues evaluated in this study.Nomenclature: Acetochlor; acifluorfen; bentazon; chlorimuron-ethyl; diclosulam; diuron; flumioxazin; imazapic; prometryn; pyroxasulfone; pyrithiobac-sodium; S-metolachlor; trifloxysulfuron-sodium; cereal rye; Secale cereal L.; common vetch; Vicia villosa L.; cotton, Gossypium hirsutum L.; crimson clover, Trifolium incarnatum L.; daikon radish, Raphanus sativis L.; oat, Avena sativa L.; peanut, Arachis hypogaea L.; winter wheat, Triticum aestivum L.

Invasive winter annual grass infestations on rangeland accumulate large quantities of litter on the soil surface, as plants senesce yearly and decompose slowly. It has been speculated that winter annual grass litter can adsorb soil-active herbicides and reduce overall performance. Three experiments were conducted from 2017 to 2018 at the Colorado State University Weed Research Laboratory to evaluate interception and subsequent desorption of herbicides applied to litter from three invasive winter annual grass species with simulated rainfall. Imazapic, rimsulfuron, and indaziflam were applied to medusahead [Taeniatherum caput-medusae (L.) Nevski], ventenata [Ventenata dubia (Leers) Coss.], and downy brome (Bromus tectorum L.) litter at two amounts (equivalent to 1,300 and 2,600 kg ha−1). Rainfall was simulated at 3, 6, 12, and 24 mm at 0, 1, and 7 d after herbicide application. Herbicide concentration from the collected rainfall was measured using liquid chromatography–tandem mass spectrometry. At 2,600 kg ha−1, B. tectorum herbicide interception was 84.3%, while V. dubia and T. caput-medusae averaged 76% herbicide interception. There were no differences in desorption among the three litter types. Simulated rainfall at 0 d after application recovered 100% of the intercepted rimsulfuron and imazapic from B. tectorum litter, while recovery decreased to 65% with rainfall at 1 or 7 d after application. Only 54% of indaziflam could be recovered at 0 d, and recovery decreased to 33% when rainfall was applied at 1 or 7 d after application. Applying soil-active herbicides before forecasted rain or tank mixing with a POST herbicide to provide initial control could potentially increase the amount of herbicide reaching the soil and provide more consistent invasive winter annual grass control.

The water footprint (WF) is an important indicator for water management, as it identifies the amount of water used directly and indirectly by a consumer or a product. The objective of this study is to analyze the sugarcane industry's WF in Brazil's Northeast region for the 2016/17 and 2017/18 harvest seasons. The blue, green and grey WFs of sugarcane were quantified, as well as the blue WFs of the production processes of ethanol and sugar, the main subproducts of sugarcane for both harvests. The work was carried out in an area with 18.42 hectares of sugarcane crops under sprinkler irrigation. The process of sugarcane production and use of pesticides was surveyed and meteorological data for the production period was collected. Right after, mathematical models were used to estimate the blue, green and grey WFs. The WF of the sugarcane was found to be 2,364.87 m³ t-1 and 1,043.92 m³ t-1 for the first and second harvest, respectively. The grey WF made up the largest part of this value, mostly due to use of the pesticides Diuron 800 and Imazapic. The processes of ethanol and sugar production, meanwhile, were found to have a blue WF of approximately 10 m³ t-1 and 5 m³ t-1, respectively. From these results, we can conclude that the WF is an effective indicator for monitoring water use in the production cycle of sugarcane and its subproducts, and that the use of fewer polluting pesticides would aid in reducing the WF of this cycle.

Peanut is one of the most important oilseed crop grown in China. Purple nutsedge (Cyperus rotundus L.) is a competitive perennial weed, which infests peanut fields in south China and causes considerable peanut yield losses. Information on the interference of purple nutsedge on peanut and its economic threshold (ET) in field is an integral component of integrated weed management system. This will help growers use herbicides more legitimately and reduce the amount of herbicide that is discharged into the environment. 2-year experiments were conducted to assess the infestation effects of purple nutsedge on peanut in pure stands (nutsedge density 0, 5, 10, 20, 40, 80, 120 and 160 plants m−2) and in natural weed infestation, respectively. Furthermore, the ET of purple nutsedge in peanut was determined according the quadratic equation reported by Cousens. The biomass of purple nutsedge with a density of 160 plants m−2 in pure stand was less than that of natural weed infestation treatment. Compared with natural weed infestation treatments, lower yield loss in treatment of nutsedge 160 plants m−2 indicated weaker interference on peanut. But the ET of purple nutsedge in peanut came down to 4–5 plants m−2. The higher price of peanut than the cost of weed control and very high efficiency (90%) of imazapic could be the probable reasons.

Ventenata (Ventenata dubia [Leers] Coss.) is an exotic annual grass that can invade intermountain rangeland plant communities, where it can form monotypic stands, degrade wildlife habitat, and reduce livestock forage. There is limited information on ventenata control in rangelands as it has only recently been identified as a substantial problem. Imazapic is a pre-emergent herbicide commonly used to control other exotic annual grasses and, therefore, is likely to control ventenata in rangelands. We evaluated five application rates of imazapic (0 − 175 g ae ∙ ha− 1) on ventenata and other exotic annual grass control and plant community response at two rangeland sites in 2 yr (2014 and 2015). Imazapic reduced exotic annual grass (largely ventenata) cover and density, with greater control with increasing imazapic rates. Exotic annual grass density at the highest levels of control (82%−94%) was 184 − 299 plants ∙ m− 2 the first yr after imazapic application. Exotic annual grasses fully recovered in the second or third yr after imazapic application. Bare ground generally increased with imazapic application. However, density of perennial vegetation (grasses and forbs) did not vary among treatments. Perennial vegetation cover generally did not increase with imazapic control of ventenata and other exotic annual grasses. Imazapic can control ventenata; however, even at the highest rates, control was not enough to shift the dominance from exotic annual species to perennial species. Integrating other treatments with imazapic application may be a strategy to improve ventenata control and increase perennial vegetation and will require further investigation. The difficulty and likely expense of achieving substantial and lasting control of ventenata suggest, similar to other exotic annual grasses, that preventing ventenata invasion and dominance should be a high management priority.

In the plantation of sugarcane, Imazapic has used pre- or post-emergence, alone or in combination with other herbicides. When applied to the soil in pre-emergence, Imazapic can undergo the sorption, leaching and/or degradation processes due to physical, chemical and biological effects, besides being absorbed by weeds. The objective of this work was to evaluate the interaction and mobility of the Imazapic herbicide in the soil where the soil columns with a dystrophic Yellow Ultisol (YUd) and a dystrophic Red-Yellow Oxisol (RYOd) from northeastern Brazil were used. The higher adsorption potential of the RYOd is associated with higher clay content, higher Fed and Feo concentrations, and soil acidic pH. The CDE – 2 sorption sites model adequately represented the experimental data from the Imazapic breakthrough curves to the RYOd and YUd soils. From the Kd partition coefficients for RYOd and YUd, high values of the GUS index (5.94 and 7.04, respectively) were calculated, confirming the high leaching potential of the Imazapic molecule in these soils. RESUMO Na plantação de cana-de-açúcar, o Imazapic tem sido usado em pré ou pós-emergência, isoladamente ou em combinação com outros herbicidas. Quando aplicado ao solo em pré-emergência, o Imazapic pode sofrer os processos de sorção, lixiviação e/ou degradação por efeitos físicos, químicos e biológicos, além de ser absorvido por plantas daninhas. O objetivo deste trabalho foi avaliar a interação e mobilidade do herbicida Imazapic no solo onde foram utilizadas colunas de solo com um Argissolo Amarelo distrófico (YUd) e um Latossolo Vermelho-Amarelo distrófico (RYOd) do Nordeste do Brasil. O maior potencial de adsorção do RYOd está associado ao maior teor de argila, maiores concentrações de Fed e Feo e pH ácido do solo. O modelo CDE - 2 de dois sítios de sorção representou adequadamente os dados experimentais das curvas de eluição do Imazapic para os solos RYOd e YUd. A partir dos coeficientes de partição Kd para RYOd e YUd, altos valores do índice GUS (5,94 e 7,04, respectivamente) foram calculados, confirmando o alto potencial de lixiviação da molécula Imazapic nesses solos.

Made available in DSpace on 2022-05-01T08:44:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Successive mowing are the major maintenance costs of lawns. Thus, both the expenditure with mowing and the visual and physiological aspect of the lawn have led to the search for alternatives to mechanical management. Thus, this work aimed to study the effects of different rates of imazapic herbicide applied alone or combined with imazapyr as a growth regulator of Bahiagrass (Paspalum notatum) and St. Augustine grass (Stenotaphrum secundatum). The experimental design was a randomized block with four replicates, and the treatments consisted of six rates of imazapic herbicide (35; 70; 105; 140; 175 and 210 g a.i. ha-1) for both species, three rates of imazapic + imazapyr in tank mix (15.57 + 5.25; 23.625 + 7.875; 32.5 + 10.5 g a.i. ha-1) for Bahiagrass and four rates of imazapic + imazapyr mixture (7.875 + 2.625; 15.57 + 5.25; 23.625 + 7.875; 32.5 + 10.5 g a.i. ha-1) for St. Augustine grass. The effect of the treatments was evaluated by observing visible injury symptoms, canopy height, height and number of inflorescences and total dry matter of clippings. Applications of imazapic alone or combined with imazapyr were effective in reducing plant height, number and height of inflorescences and total amount of dry matter of clippings produced by Bahiagrass plants. Imazapic provided satisfactory control of St. Augustine growth, but its utilization caused an increase in the number of inflorescences present in the lawns. São Paulo State University Department of Agronomy State University of Mato Grosso Department of Plant Science São Paulo State University São Paulo State University Department of Plant Science São Paulo State University

Weeds represent an increasing challenge for crop systems since they have evolved adaptability to adverse environmental conditions, such as salinity stress. Herbicide effectiveness can be altered by the quality of water in which the weed is growing. This research aimed to study the combined effect of salt stress and recurrent selection with a sublethal dose of imidazolinone herbicides in the shifting of the sensitivity of Echinochloa colona (L.) Link (junglerice) to imidazolinone herbicides. This study was divided into two experiments, in experiment I, three recurrent selection cycles were conducted in Pelotas/RS/Brazil with imazapic + imazapyr at 0.125× the field rate, and in experiment II, three recurrent selection cycles were conducted in Fayetteville/AR/USA with imazethapyr, at 0.125× the recommended dose. Salt stress was implemented by irrigation with 120 mM sodium chloride (NaCl) solution. The effective dose for 50% control of the population (ED50) values increased from the field population to the second generation (G2) after recurrent selection with a sublethal dose of imidazolinone combined with salt stress, supporting the hypothesis of reduced susceptibility by the combination of these abiotic factors. Recurrent exposure to a sublethal dose of imazapic + imazapyr or imazethapyr, combined with salt stress, reduced susceptibility of Echinochloa colona (L.) plants to imidazolinone herbicides.

Pre‐emergent herbicides are frequently used to control exotic annual plants prior to seed‐based restoration, but seeding must generally wait until herbicide toxicity has waned. The emerging seed‐enhancement technology of herbicide protection pods (HPP) allows for simultaneous seeding and herbicide application by protecting desirable seeds inside pods or pellets containing activated carbon, allowing for single‐entry and potentially cost‐saving wildland restoration approaches. This technology has shown promise in multiple recent lab and field experiments. However, the effect of pod size on efficacy has not been formally investigated, and important small‐seeded species have either not been tested or have shown less‐promising results when used with this technology. Using emergence trials in two different laboratory environments with two small‐seeded species important to restoration in the semi‐arid western United States (Wyoming big sagebrush [Artemisia tridentata Nutt ssp. wyomingensis] and Sandberg bluegrass [Poa secunda J Presl]), we investigated if HPP size affected early performance and protection from herbicide (imazapic), as well as how different sizes of HPPs compared to bare seed. For both species, smaller HPP sizes selected to match optimal seeding depths showed up to two‐fold higher emergence and aboveground biomass than larger pellets and still maintained protection from herbicide toxicity. Both species also showed 50–90% reductions in emergence and aboveground biomass due to incorporation into HPPs in general, resulting in only one species (bluegrass) showing the desired effect of HPPs: higher success than bare seed in the presence of herbicide. We suggest that additional experimentation to improve this promising technology is warranted.

The present study sought to verify the existence of interactions between the soil water conditions, nitrogen and herbicides commonly used to control alexandergrass in irrigated rice crop. The experimental design was completely randomized, arranged in a 2 x 3 x 4 factorial scheme, corresponding to two soil water conditions (5 cm water depth and 100% soil water holding capacity [WHC]), three nitrogen doses (0, 80 and 160 kg of N ha-1) and four doses of herbicides (0, 0.5, 1 and 2 times the registration dose). The herbicides evaluated were cyhalofop-butyl, imazapyr + imazapic and imazethapyr. The treatments were repeated four times. Phytotoxicity and dry mass were evaluated 28 days after application. For cyhalofop-butyl and imazapyr + imazapic, the phytotoxicity at 100% WHC and 5 cm water depth conditions was higher in treatments with nitrogen fertilization. However, for imazethapyr under the 100% WHC condition of soil increased phytotoxicity in the absence of nitrogen fertilization. For the flooded condition, from the dose of 35 g of a.i. ha-1, the result in the control for the herbicide imazethapyr was optimized under the conditions of fertilization with 80 and 160 kg of N ha-1. Cyhalofop-butyl and imazapyr + imazapic undergo synergistic interaction with nitrogen fertilization and water status in the control efficiency, yet with imazethapyr, the synergistic interaction only occurs under 100% of soil WHC. RESUMO Buscou-se constatar a existência de interações entre condições hídricas do solo, nitrogênio e herbicidas comumente utilizados para controle de papuã no cultivo do arroz irrigado. O delineamento experimental utilizado foi inteiramente casualizado, arranjado em um esquema fatorial 2 x 3 x 4, sendo duas condições hídricas do solo (lâmina d’água de 5 cm e 100% de capacidade de retenção de água do solo), três doses de nitrogênio (0, 80 e 160 kg de N ha-1) e doses de herbicidas (0, 0,5, 1 e 2 vezes a dose de registro). Os herbicidas avaliados foram cyhalofop-butyl, imazapyr + imazapic e imazethapyr. Os tratamentos foram repetidos quatro vezes. Avaliou-se a fitotoxicidade e a massa seca aos 28 dias após a aplicação. Para cyhalofop-butyl e imazapyr + imazapic, a fitotoxicidade nas condições de 100% da capacidade de retenção de água do solo e lâmina d’água foi superior nos tratamentos com adubação nitrogenada. Entretanto, para imazethapyr na condição de 100% da capacidade de retenção de água do solo houve aumento de 45% da fitotoxicidade na ausência de adubação nitrogenada em comparação à condição com adubação. Para a condição de alagamento, a partir da dose de 35 g de i.a. ha-1, o resultado no controle para o herbicida imazethapyr foi otimizado nas condições de adubação com 80 e 160 kg de N ha-1. Cyhalofop-butyl e imazapyr + imazapic sofrem interação sinérgica com a adubação nitrogenada e a condição hídrica na eficiência do controle, já com imazethapyr, a interação sinérgica só ocorre em 100% da capacidade de retenção de água do solo.

1. Annual grass invasion is transforming the western United States and driving a need for restoration techniques that can both reduce exotic annual grass abundance and allow revegetation of native species. Pre‐emergent herbicides can provide control of annual grasses, but when applied concurrently with direct seeding efforts, the herbicide can also impact seeded species. Indaziflam is a relatively new herbicide that may provide extended control of exotic annual grasses, but little is known about its effects when applied at the time of seeding. 2. In this study, we compared indaziflam to imazapic, a popular herbicide used in restoration efforts, to understand how indaziflam affects plant establishment of a native species, bluebunch wheatgrass Pseudoroegneria spicata (Pursh) Á. Löve. We created furrows on half our treatments to limit herbicide concentrations and potentially create a safe‐site for seeding bluebunch wheatgrass. 3. During the 2‐year study, indaziflam provided consistent control of the annual weed, downy brome Bromus tectorum L., whereas imazapic control decreased sharply with time. Indaziflam and imazapic decreased bluebunch wheatgrass seedling emergence by 96% and 46%, and 2‐year plant density by 91% and 65%, respectively, compared to non‐herbicide treatments. Both herbicides reduced aboveground biomass of bluebunch wheatgrass by over 85% 2 years after seeding/herbicide application. 4. Furrow treatments mitigated imazapic's effect on bluebunch wheatgrass, but did not limit the impacts by indaziflam. 5. Herbicide can be used in conjunction with direct seeding efforts, but mitigation of the effects to native seeds will depend on herbicide specifics such as mode of action and soil mobility.

Research from the 1980s reported sweep cultivation being a cost-effective component in an integrated system to manage weeds in peanut. Previous weed management research conducted on organic peanut indicated that repeated cultivation with a tine weeder was an effective component in that production system. Studies were conducted in Tifton, GA, from 2014 through 2017 to determine whether tine weeding can be integrated with herbicides in conventional peanut production to supplement herbicides. Experiments evaluated a factorial arrangement of eight herbicide combinations and two levels of cultivation using a tine weeder. Herbicides were labeled rates of ethalfluralin PRE, S-metolachlor PRE, imazapic POST, ethalfluralin PRE + S-metolachlor PRE, ethalfluralin PRE + imazapic POST, S-metolachlor PRE + imazapic POST, ethalfluralin PRE + S-metolachlor PRE + imazapic POST, and a nontreated control. The herbicides chosen were based on knowledge of the weed species composition at the research sites and their common use in peanut. Cultivation regimes were cultivation with a tine weeder (six times at weekly intervals) and a noncultivated control. Benefits of tine weeding supplementing control from herbicides varied according to herbicide and weed species. For example, annual grasses were effectively controlled (88% to 97%) by ethalfluralin or S-metolachlor and did not need cultivation to supplement control provided by the herbicides. However, imazapic alone did not effectively control (54% to 75%) annual grasses and needed supplemental control from cultivation with the tine weeder. Similarly, imazapic effectively controlled (84% to 93%) smallflower morningglory and did not require cultivation to supplement control from the herbicide. However, cultivation with the tine weeder improved smallflower morningglory control (76% to 95%) when supplementing ethalfluralin or S-metolachlor. Peanut yields did not respond to any of the herbicide combinations integrated with cultivation using the tine weeder. During the time period when peanut was cultivated, there was greater total rainfall and more days of rainfall events in 2014 and 2017 compared with the other years. Rainfall and wet soils reduced the performance and weed control benefits of the tine weeder. This highlights the risk of depending on cultivation for weed control.

Minimizing the negative ecological impacts of exotic plant invasions is one goal of land management. Using selective herbicides is one strategy to achieve this goal; however, the unintended consequences of this strategy are not always fully understood. The recently introduced herbicide indaziflam has a mode of action not previously used in non-crop weed management. Thus, there is limited information about the impacts of this active ingredient when applied alone or in combination with other non-crop herbicides. The objective of this research was to evaluate native species tolerance to indaziflam and imazapic applied alone and with other broadleaf herbicides. Replicated field plots were established at two locations in Colorado with a diverse mix of native forbs and grasses. Species richness and abundance were compared between the nontreated control plots and plots where indaziflam and imazapic were applied alone and in combination with picloram and aminocyclopyrachlor. Species richness and abundance did not decrease when indaziflam or imazapic were applied alone; however, species abundance was reduced by treatments containing picloram and aminocyclopyrachlor. Species richness was only impacted at one site 1 yr after treatment (YAT) by these broadleaf herbicides. Decreases in abundance were mainly due to reductions in forbs that resulted in a corresponding increase in grass cover. Our data suggest that indaziflam will control downy brome (Bromus tectorumL.) for multiple years without reduction in perennial species richness or abundance. IfB. tectorumis present with perennial broadleaf weeds requiring the addition of herbicides like picloram or aminocyclopyrachlor, forb abundance could be reduced, and in some cases there could be a temporary reduction in perennial species richness.

Soil moisture can alter the transport and permanence of pre-emergent herbicides. The objective of this work was to evaluate the influence of water availability in the soil on the leaching of a commercial mixture of the herbicides imazapyr + imazapic, as well as the carryover effect of this herbicide in corn planted in succession to soybean. The experiment was carried out in leaching columns in a randomized block design with 4 replications. A 3x3x2 factorial scheme was used, with factor A being the irrigation (130%, 100% and 70% of field capacity (CC)), factor B the doses of the commercial mixture of the herbicides imazapyr + imazapic (0.00+ 0.00; 52.5 + 17.5 and 105 + 35 g ha-1) and factor C at soil depth (0-0.3 m and 0.3-0.6 m). Soybean sowing was performed at the top of the columns and immediately after herbicide mixture was applied. After 120 days the columns were opened, generating two sections, where corn (Zea mays) and the other watermelon (Citrullus lanatus) were sown as a bioindicator of herbicide residue. The fluorescence parameters of chlorophyll a at 15 and 30 days after germination (DAG) and shoot dry matter accumulation at 30 DAG were evaluated. There was greater retention of the herbicide imazapyr + imazapic at a depth of 0-0.3m at 70% CC condition and leaching at a depth of 0.3-0.6m at 130% CC condition, with a reduction in the mass accumulation of watermelon plants. The herbicide has a carryover potential for corn cultivation in soils maintained at 70% CC. A umidade do solo pode alterar o transporte e a permanência de herbicidas pré-emergentes. O objetivo deste trabalho foi avaliar a influência da disponibilidade de água no solo na lixiviação da mistura comercial dos herbicidas imazapyr+imazapic, bem como o efeito carryover deste herbicida no milho semeado em sucessão à soja. O experimento foi desenvolvido em colunas de lixiviação em delineamento de blocos ao acaso com 4 repetições. Foi utilizado esquema fatorial 3x3x2, sendo o fator A as lâminas de irrigação (130%, 100% e 70% da capacidade de campo (CC)), o fator B as doses da mistura comercial dos herbicidas imazapyr + imazapic (0,00+0,00; 52,5+17,5 e 105+35 g ha-1) e o fator C a profundidade (0-0,3 m e 0,3-0,6 m). A semeadura da soja foi realizada no topo das colunas e imediatamente após foi realizada a aplicação da mistura dos herbicidas. Após 120 dias as colunas foram abertas, gerando duas canaletas, onde em uma foi semeado o milho (Zea mays) e na outra melancia (Citrullus lanatus) como bioindicadora do resíduo dos herbicidas. Foram avaliados os parâmetros fluorescência da clorofila a aos 15 e 30 dias após germinação (DAG) e acúmulo de matéria seca de parte aérea aos 30 DAG. Houve maior retenção do herbicida imazapyr+imazapic na profundidade de 0-0.3m na condição de 70% CC e lixiviação para a profundidade de 0,3-0,6 m na condição de 130% CC, com redução no acúmulo de massa das plantas de melancia. O herbicida tem potencial carryover para a cultura do milho em solos mantidos a 70% CC. &nbsp

Revegetation of exotic annual grass − invaded rangeland with preemergent herbicides is challenging because seeding is delayed until herbicide toxicity has diminished, but at this time, exotic annuals can be reinvading. Incorporating seeds into activated carbon pellets may allow seeding to occur at the same time as exotic annuals are controlled with a preemergent herbicide because activated carbon can neutralize the herbicide in the microsite around seeds. I evaluated using activated carbon pellets with six species seeded at the same time imazapic was applied to control exotic annual grasses at two sites. Two of the six species establish enough at one site to evaluate the effects of pellets. These two bunchgrasses had greater density and growth (height, leaf length, number of stems and leaves) when incorporated into activated carbon pellets compared with seeded as bare seed. This demonstrates activated carbon pellets can be used to protect seeded bunchgrasses from imazapic applied to control exotic annuals.

Medusahead (Taeniatherum caput-medusae [L.] Nevski) and other exotic annual grasses have invaded millions of hectares of sagebrush (Artemisia L.) steppe. Revegetation of medusahead-invaded sagebrush steppe with perennial vegetation is critically needed to restore productivity and decrease the risk of frequent wildfires. However, it is unclear if revegetation efforts provide long-term benefits (fewer exotic annuals and more perennials). The limited literature available on the topic questions whether revegetation efforts reduce medusahead abundance beyond 2 or 3 yr. We evaluated revegetation of medusahead-invaded rangelands for 5 yr after seeding introduced perennial bunchgrasses at five locations. We compared areas that were fall-prescribed burned immediately followed by an imazapic herbicide treatment and then seeded with bunchgrasses 1 yr later (imazapic-seed) with untreated controls (control). The imazapic-seed treatment decreased exotic annual grass cover and density. At the end of the study, exotic annual grass cover and density were 2-fold greater in the control compared with the imazapic-seed treatment. The imazapic-seed treatment had greater large perennial bunchgrass cover and density and less annual forb (predominately exotic annuals) cover and density than the untreated control for the duration of the study. At the end of the study, large perennial bunchgrass density average 10 plant·m-2 in the imazapic-seed treatment, which is comparable with intact sagebrush steppe communities. Plant available soil nitrogen was also greater in the imazapic-seed treatment compared with the untreated control for the duration of the study. The results of this study suggest that revegetation of medusahead-invaded sagebrush steppe can provide lasting benefits, including limiting exotic annual grasses.

To determine the spectrum of weed control and peanut tolerance with pyroxasulfone in Oklahoma. Study Design: Randomized complete block design with four replications. Place and Duration of Study: Oklahoma State University Caddo Research Station near Ft. Cobb (35.091o N, 98.275o W) in southwestern Oklahoma during the 2013-2014 growing seasons. Methodology: Herbicides were applied with a CO2 compressed air backpack sprayer using Teejet 110015XR nozzles that delivered 93 L ha-1 at 180kPa. Weed control and peanut injury were visually estimated on a scale of 0 indicating no control or plant death to 100 indicating complete control or plant death, relative to the untreated control. Peanut yields were obtained by digging each plot separately, air-drying in the field for 4 to 7 d, and harvesting peanut pods from each plot with a combine. Visual estimates of weed control and peanut yield were subjected to analysis of variance to test effects of postemergence (POST) herbicide and application timing and means were compared with Fisher’s Protected LSD test (0.05). Results: In 2013, only treatments that controlled Urochloa texana > 85% were those that included pendimethalin plus pyroxasulfone applied preemergence (PRE) and imazapic applied late postemergence (LPOST). Ipomoea hederacea control using either pendimethalin applied preplant incorporated (PPI) or flumioxazin applied PRE and imazethapyr applied POST was > 75%. In 2014, herbicide systems that included imazapic applied POST controlled I. hederacea at least 98% while no other herbicide systems provided better than 78% control. Peanut stunting (4 to 13%) was observed in 2013 with all PPI and PRE treatments. In 2013 and 2014, pyroxasulfone plus pendimethalin systems applied PRE followed by imazapic applied LPOST produced the greatest peanut stunting. Conclusion: These results indicate that pyroxasulfone is an effective herbicide for weed control in Oklahoma peanut production. Although no peanut yield reductions were observed, the early season stunting in isolated instances should be noted.

Competition control is essential for successful eucalyptus plantation establishment, yet few selective herbicides have been identified. Five herbicides, flumioxazin, imazamox, imazapic, oxyfluorfen, and sulfometuron methyl, were evaluated at either pre- or post-weed emergence timing for selective weed control in the establishment of Eucalyptus benthamii, a frost-tolerant species showing promise for commercial plantations in the southeastern United States and southern Brazil. Herbicides were applied at two or three rates and compared to a non-treated control and to near-complete weed control obtained with repeated glyphosate directed sprays. Herbicides were most efficacious when applied prior to weed emergence, at 2 weeks after planting 16-week-old containerized eucalyptus seedlings. Pre-emergence imazapic treatments resulted in broad-spectrum and persistent weed control, with 77–82% bare-ground at 60 days after treatment, but both pre- and post-emergence applications of imazapic caused excessive eucalyptus injury at the highest rate tested. Imazapic, sulfometuron, and imazamox were most effective for grass control. Both timings of flumioxazin were effective for forb control at the early assessment. All pre-emergence treatments enhanced stem volume compared to the non-treated control, but post-emergence treatments did not, suggesting the need for early weed control to facilitate E. benthamii growth. Pre-emergence applications of medium and high sulfometuron, low imazapic, high imazamox, and high oxyfluorfen rates increased stem volume four-fold to six-fold compared to the non-treated control. Repeated glyphosate directed sprays increased stem volume nearly three-fold compared to the control. These results confirm one early report of flumioxazin effectiveness and identify imazamox and imazapic as new selective herbicides for eucalyptus culture.

On the Ground Cheatgrass has transformed secondary succession in arid sagebrush plant communities in the Great Basin by providing a fine-textured, early maturing fuel that increases the chance, rate, spread, and season of wildfires. The best known method to suppress cheatgrass densities and associated fuels is through the establishment of perennial grasses. Crested wheatgrass plots seeded the first fall following the wildfire (2006) averaged an establishment of 9.6 plants/m2 compared with plots seeded the second fall at 3.9 plants/m2. Native perennial species bluegrass and squirreltail experienced high failure rates. Over the 2-year study, un-disced cheatgrass plots averaged more than 1,350 cheatgrass seeds/m2, while plots receiving our April/May discing application averaged fewer than 250 cheatgrass seeds/m2, an 82% reduction in cheatgrass seed bank densities, which significantly improved seeded species establishment. The use of soil-active herbicides, Imazapic (Plateau) and Sulfometuron methyl (Landmark...

Revegetation of exotic annual grass − invaded rangelands is challenging as annuals rapidly reinvade after control treatments. The most effective control of exotic annual grass is usually achieved with pre-emergent herbicides; however, species seeded simultaneously with these herbicides will likely experience nontarget damage. Thus, seeding often occurs 1 yr later to reduce herbicide effects to seeded vegetation, but by this time annual grasses may already be reinvading and limiting revegetation success. Activated carbon can be used to protect seeded species from herbicide damage because it has a high absorption capacity that can deactivate many herbicides. A pot study in a grow-room suggested that a pod containing activated carbon and seeds, herbicide protection pods (HPPs), may allow desired species to be seeded simultaneously with annual grass control with the pre-emergent herbicide imazapic. However, HPPs have not been field tested. We evaluated two seeding treatments (crested wheatgrass (Agropyron desertorum [Fisch.] Schult.) incorporated into HPPs and bare seed, simultaneously with an imazapic application to control annual grasses at two sites invaded by cheatgrass (Bromus tectorum L.) and medusahead (Taeniatherum caput-medusae [L.] Nevski). Crested wheatgrass abundance was 300% greater with HPPs compared with bare seed in late June. Imazapic application reduced exotic annual grass density at both sites by approximately half. These results suggest that HPPs can be used to allow desired species to be seeded simultaneously with imazapic application. This will allow seeded species a longer window to become established before experiencing pressure from exotic annuals and enable a single-entry approach compared with multiple entries currently employed to revegetate annual grass − invaded rangelands. Though further field testing is needed, in particular with multiple species and higher herbicide applications rates, these results suggest that HPPs could improve our ability to restore and revegetate exotic annual grass − invaded rangelands.

North America's remaining natural grassland communities provide habitat for native flora and fauna. We conducted a study to compare the efficacy of herbicides in control of the invasive Japanese honeysuckle (Lonicera japonica Thunb.) applied at times when most native plant species are dormant. Six herbicide mixtures (glyphosate, glyphosate + imazapyr, glyphosate + imazapic, imazapyr, triclopyr + diflufenzopyr, and metsulfuron methyl + diflufenzopyr) were applied once each in three seasons to assess the effect of application timing of each mixture on honeysuckle control. Herbicides were applied with a CO2 pressurized sprayer at three sites in a randomized complete block design. Pretreatment sampling indicated that Japanese honeysuckle constituted over 70% of plant cover at the study sites. Post-treatment sampling was conducted 60 days, 180 days, 420 days, and 540 days after the final application. All mixtures in all application seasons decreased percent cover of honeysuckle with varying effective...

Invasive winter annual grasses such as downy brome (Bromus tectorum L.) are a threat to native ecosystems throughout the United States. Downy brome is able to exploit moisture and nutrients throughout the fall and early spring before native plants break dormancy. This results in decreased native species abundance and development of monotypic downy brome stands. Short-termdowny brome management has been shown to be effective; however, the soil seed reserve has often been overlooked, although it's the mechanismresponsible for rapid reestablishment. This field study was conducted at two sites in Colorado to evaluate the longevity of the downy brome soil seed reserve and its implications on long-termdowny brome control. Glyphosate plus adjuvant applications were made for 0, 1, 2, 3, 4, or 5 consecutive years. Downy brome and perennial grass biomass harvests were conducted yearly to determine changes in species composition. In addition, soil cores were collected to evaluate the yearly variation and depletion of the downy brome soil seed bank in response to consecutive glyphosate applications. We found that 1–3 yr of consecutive glyphosate treatments were insufficient to deplete the downy bromesoil seed bank. Downy brome biomass and the soil seed bank recoveredwithin 1–2 yr after glyphosate treatmentswere terminated; however, 4 and 5 consecutive yr of glyphosate applications were sufficient to control downy brome through depletion of the soil seed bank. Managing downy brome for 4–5 consecutive yr resulted in a 4- to 9-fold increase in perennial grass biomass. These data suggest that long-term management of downy brome is dependent on eliminating the soil seed bank using a multiyear approach.

Background Indaziflam is a cellulose-biosynthesis-inhibiting (CBI) herbicide that is a unique mode of action for resistance management and has broad spectrum activity at low application rates. This research further explores indaziflam's activity on monocotyledons and dicotyledons and evaluates indaziflam's potential for restoring non-crop sites infested with invasive winter annual grasses. Results Treated Arabidopsis, downy brome, feral rye and kochia were all susceptible to indaziflam in a dose-dependent manner. We confirmed that indaziflam has increased activity on monocots (average GR50 = 231 pm and 0.38 g AI ha-1 ) at reduced concentrations compared with dicots (average GR50 = 512 pm and 0.87 g AI ha-1 ). Fluorescence microscopy confirmed common CBI symptomologies following indaziflam treatments, as well as aberrant root and cell morphology. Across five application timings, indaziflam treatments resulted in superior invasive winter annual grass control 2 years after treatment (from 84 ± 5.1% to 99 ± 0.5%) compared with imazapic (36% ± 1.2%). Indaziflam treatments significantly increased biomass and species richness of co-occurring species 2 years after treatment. Conclusion Indaziflam's increased activity on monocots could provide a new alternative management strategy for long-term control of multiple invasive winter annual grasses that invade >23 million ha of US rangeland. Indaziflam could potentially be used to eliminate the soil seed bank of these invasive grasses, reduce fine fuel accumulation and ultimately increase the competitiveness of perennial co-occuring species. © 2017 Society of Chemical Industry.

The influence of various concentrations of imazapic residues (0–800 μg kg–1) on the growth, chlorophyll content, and photosynthetic characteristics of maize seedlings was studied in a greenhouse pot experiment. Plant height, root length, shoot dry mass, root dry mass, and total dry mass of maize declined with the increase of imazapic residue concentrations. The root/shoot ratio initially decreased and then increased in presence of imazapic, which indicated that the effects of imazapic residues on plant height and root length might differ in maize seedlings. Lowered chlorophyll content and net photosynthetic rate were observed in leaves of maize seedlings in all treatments and indicated a dose-response relationship to imazapic concentrations. Intercellular carbon dioxide concentration, transpiration rate, and stomatal conductance also declined to varying extents, but the chlorophyll a/b ratio increased gradually together with the increase of imazapic residue concentrations. Generally, the maize seedlings were negatively affected by the imazapic residues in soil. Response of root length and biomass to imazapic residues could be the important index for maize variety selection.

Imidazolinones are a family of herbicides that are used to control a broad range of weeds. Their high persistence and leaching potential make them probable risk to the ecosystems. In this study, biochar, the biomass-derived solid material, was produced from oil palm empty fruit bunches (EFB) and rice husk (RH) through pyrolysis process. Feedstock and pyrolysis variables can control biochar sorption capacity. Therefore, the present study attempts to evaluate effects of three pyrolysis variables (temperature, heating rate and retention time) on abilities of biochars for removal of imazapic and imazapyr herbicides from soil. Response surface methodology (RSM) was used for optimizing the variables to achieve maximum sorption performance of the biochars. Experimental data were interpreted accurately by quadratic models. Based on the results, sorption capacities of both biochars raised when temperature decreased to 300 °C, mainly because of increased biochars effective functionality in sorption of polar molecules. Heating rate of 3°C/min provided optimum conditions to maximize the sorption capacities of both biochars. Retention time of about 1 h and 3 h were found to be the best for EFB and RH biochars, respectively. EFB biochar was more efficient in removal of the herbicides, especially imazapyr due to its chemical composition and higher polarity index (0.42) rather than RH biochar (0.39). Besides, higher cation exchange capacity (CEC) values of EFB biochar (83.90 cmolc/kg) in comparison with RH biochar (70.73 cmolc/kg) represented its higher surface polarity effective in sorption of the polar herbicides.

Background: Information on the carryover of herbicides applied to the destruction of cotton stalks, as well as the withdrawal period necessary to prevent the development and productivity of the crop in succession from being affected are limited in the literature. Objective: The objective was to identify the carryover effect promoted by herbicides used in the management of the destruction of cotton stalks and to estimate the host free period for sowing soybean in succession. Methods: Two individual experiments were conducted simultaneously, one for single application and the other for sequential application of herbicide treatments. The experiments were installed in a factorial scheme (15x5), in a randomized block design with four replications. The first factor evaluated was herbicide treatments and the second factor was five soybean sowing times after application (0, 30, 60, 90 and 120 days). The herbicides used in the treatments were 2,4-D, glyphosate, saflufenacil, [imazapic + imazapyr], dicamba, fluroxypyr and sulfentrazone. Results: As this work was conducted, the results provide a carryover indicator. It is concluded that the single application and the sequential application of the glyphosate + dicamba + saflufenacil treatment has great carryover potential for soybean crops, with the host free period for sowing the crop exceeding 120 days after application. Conclusions: The treatments 2,4-D, 2,4-D + glyphosate, glyphosate + saflufenacil + fluroxypyr had the lowest host free period intervals, even when in sequential application. The treatment with application of 2,4-D alone showed the lowest carryover potential for soybean.

The IMI-herbicides rice package has been recognized by all means among the most efficient chemical approaches for weedy rice control nowadays. Inevitably, the continuous and sole dependence, as well as ignorance on the appropriate use of imidazolinone herbicides in the IMI-herbicides rice package by rice growers has caused the development of herbicide resistance in weedy rice populations across many IMI-herbicides rice package adopted countries, inclusive of Malaysia. Hence, a comprehensive study was conducted to elucidate the occurrence, level, and mechanisms endowing resistance to IMI-herbicides on field-reported resistant (R) weedy rice populations collected from IMI-rice fields in Kampung Simpang Sanglang, Perlis (A), Kampung Behor Mentalon, Perlis (B), and Kampung Sungai Kering, Kedah (C). The collected weedy rice populations were compared with a susceptible weedy rice population (S), an imidazolinone-resistant rice cultivar (IMI-rice), and a susceptible local rice cultivar (MR219). Dose-response experiments were carried out using commercial IMI-herbicides (premix of imazapic and imazapyr) available in the IMI-herbicides rice package, in the seed bioassay and whole-plant dose-response. Based on the Resistance Index (RI) quantification in both experiments, the cross-resistance pattern of weedy rice populations and rice varieties to imazapic and imazapyr was determined. Molecular investigation was carried out by comparing acetohydroxyacid synthase (AHAS) gene sequences between resistant (R) weedy rice populations (A, B, and C), S population, IMI-rice, and MR219. Evidently, the AHAS gene sequences of R weedy rice were identical to the IMI-rice, revealing that amino acid substitution of Ser-653-Asn occurs in both R populations and IMI-rice, but neither in MR219 nor S plants. In vitro assays were conducted using analytical grade imidazolinone herbicides of imazapic (99.3%) and imazapyr (99.6%) with seven concentrations. The results demonstrated that the AHAS enzyme extracted from R populations and IMI-rice were less sensitive to IMI-herbicides in comparison to S and MR219, further supporting the IMI-herbicides resistance was conferred by target site mutation. In conclusion, the basis of imidazolinone resistance in selected populations of Malaysia weedy rice was due to a Ser-653-Asn mutation that reduced sensitivity of the target site to IMI-herbicides. The current study presents the first report of resistance mechanism in weedy rice in Malaysian rice fields.

Echinochloa crus-galli is the main weed in direct dry-seeded rice systems worldwide and is the target of most herbicide applications. Numerous cases of E. crus-galli biotypes with resistance to herbicides have been reported in different regions of the world, however, to date, no cases have been reported in Uruguay. The purpose of this research is to assess the presence of herbicide-resistant E. crus-galli in the rice fields of Uruguay. More than 40 E. crus-galli biotypes were sampled from eastern to northern regions in different years and assessed following the Herbicide Resistance Action Committee (HRAC) protocols of confirmation, using the herbicides propanil, quinclorac, clomazone, bispyribac&ndash, sodium, penoxsulam, imazapyr + imazapic, profoxidim and cyhalofop. Herbicides rates included 0, 0.125, 0.25, 0.50, 1, 2, 4 and 8 times the label rate. Most E. crus-galli biotypes (35) resulted as resistant to quinclorac. Furthermore, resistance was confirmed to propanil in at least seven biotypes, 12 to imazapyr + imazapic, and three to penoxsulam. Five biotypes showed multiple resistance to propanil and quinclorac, and one biotype was resistant to quinclorac, penoxsulam and imazapyr + imazapic. No biotype showed confirmed resistance to clomazone, bispyribac-sodium, cyhalofop or profoxidim&mdash, herbicides that ensure satisfactory control. The presence of E. crus-galli herbicide resistant-biotypes reduces herbicide options, threatening rice production in Uruguay. In this context, a redesign of the productive systems would represent an opportunity to complement the chemical control, integrating larger-scale cultural and management practices.

The objective of this work was to evaluate the distribution of imidazolinone-resistant (IMI-R) red rice (Oryza sativa) populations, the frequency of alleles conferring resistance to IMI, and the adoption of agronomic practices applied to red rice control, across growing seasons and production regions of the state of Rio Grande do Sul (RS), Brazil. In the experiment, 1,008 red rice populations were screened for resistance to IMI, 760 IMI-R red rice plants were genotyped for the acetolactate synthase (ALS) alleles conferring resistance to IMI, and 40 'Clearfield' rice growers were surveyed. IMI-R red rice populations were widespread throughout RS since the 2006/2007 growing season, with a higher initial frequency in the Depressão Central and Fronteira Sul production regions. The occurrence of IMI-R red rice ranged from 1.6 to 3.5 years after 'Clearfield' rice release. Gly654Glu was the most frequent ALS mutation in IMI-R red rice populations, which shows a gene flow from the most used 'Clearfield' rice cultivars to the red rice plants. Crop rotation systems and certified seed were used by only 30% of the surveyed growers of 'Clearfield' rice, with lower percentages in the production regions where IMI-R red rice appeared faster. Resumo: O objetivo deste trabalho foi avaliar a distribuição de populações de arroz-vermelho (Oryza sativa) resistente às imidazolinonas (R-IMI), a frequência dos alelos que conferem resistência às IMI, e a adoção de práticas agronômicas aplicadas ao controle do arroz-vermelho, em estações de cultivo e regiões produtoras de arroz do Estado do Rio Grande do Sul (RS), Brasil. No experimento, 1.008 populações de arroz-vermelho foram avaliadas quanto à resistência às IMI, 760 plantas de arroz-vermelho R-IMI foram genotipadas quanto aos alelos da acetolactato sintase (ALS) que conferem resistência às IMI, e 40 produtores de arroz 'Clearfield' foram entrevistados. As populações de arroz-vermelho R-IMI estavam amplamente distribuídas no RS, desde a época de cultivo em 2006/2007, com maior frequência inicial nas regiões orizícolas da Depressão Central e da Fronteira Oeste. A ocorrência de arroz-vermelho R-IMI variou de 1,6 a 3,5 anos após o lançamento do arroz 'Clearfield'. A mutação Gly654Glu da ALS foi mais frequente nas populações de arroz-vermelho R-IMI, o que indica a ocorrência de fluxo gênico da cultivar de arroz 'Clearfield' para as plantas de arroz-vermelho. A rotação de culturas e o uso de sementes certificadas foram adotados por apenas 30% dos produtores de arroz 'Clearfield' entrevistados, com menores percentagens nas regiões em que o arroz-vermelho R-IMI apareceu mais rápido.