scholarly journals Variable response of kochia [Kochia scoparia (L.) Schrad.] to auxinic herbicides dicamba and fluroxypyr in Montana

2015 ◽  
Vol 95 (5) ◽  
pp. 965-972 ◽  
Author(s):  
Prashant Jha ◽  
Vipan Kumar ◽  
Charlemagne A. Lim
Keyword(s):  
Great Plains ◽  
Dose Response ◽  
Weed Management ◽  
Dry Weight ◽  
Northern Great Plains ◽  
Variable Response ◽  
Kochia Scoparia ◽  
Management Tools ◽  
Herbicide Resistant ◽  
Shoot Dry Weight

Jha, P., Kumar, V. and Lim, C. A. 2015. Variable response of kochia [Kochia scoparia (L.) Schrad.] to auxinic herbicides dicamba and fluroxypyr in Montana. Can. J. Plant Sci. 95: 965–972. Herbicide-resistant kochia is an increasing concern for growers in the Northern Great Plains of United States and Canada. The objective of the research was to characterize the response of the three putative auxinic herbicide-resistant kochia inbreds (derived from accessions collected from wheat/chemical fallow fields in northern Montana) to dicamba and fluroxypyr relative to a susceptible (SUS) inbred. A dicamba dose-response study indicated that the three putative resistant inbreds (Chot-01, Chot-02, and Chot-03) had R/S ratios of 1.3 to 6.1 based on the visible control response (I50 values), and R/S ratios of 1.5 to 6.8 based on the shoot dry weight response (GR50 values). Dose-response experiments with fluroxypyr determined I50 R/S ratios of 1.4 to 5.7 and GR50 R/S ratios of 1.6 to 4.0 for the three putative resistant inbreds. The selected inbreds showed variable symptomology (phenotype) in response to dicamba and fluroxypyr. Among the three inbreds, Chot-01 exhibited the least epinasty, stem curling/swelling, and chlorosis/necrosis symptoms, and was resistant to dicamba and fluroxypyr. Growers should diversify their weed management tools to manage further spread of auxinic or multiple herbicide-resistant kochia in the region.

Growth Characterization of Kochia (Kochia scoparia) with Substitutions at Pro197or Trp574Conferring Resistance to Acetolactate Synthase–Inhibiting Herbicides

Weed Science ◽  
2013 ◽  
Vol 61 (2) ◽  
pp. 267-276 ◽  
Author(s):  
Anne Légère ◽  
F. Craig Stevenson ◽  
Hugh J. Beckie ◽  
Suzanne I. Warwick ◽  
Eric N. Johnson ◽  
...  
Keyword(s):  
Acetolactate Synthase ◽  
Dry Weight ◽  
Variable Response ◽  
Kochia Scoparia ◽  
Replacement Series ◽  
Mixed Stands ◽  
Population Total ◽  
Factors Affecting ◽  
Herbicide Resistant ◽  
Growth Characterization

Over 90% of Canadian kochia populations are resistant to acetolactate synthase (ALS)– inhibiting herbicides. We questioned whether the target site–based resistance could affect plant growth and competitiveness. Homozygous F2herbicide-resistant (HR) kochia plants with an amino acid substitution at Trp574(sources: Alberta [AB], Saskatchewan [SK], and Manitoba [MB]), or Pro197(MB, AB with two populations) were grown in replacement series with homozygous F2herbicide-susceptible (HS) plants from the corresponding heterogeneous population (total: six populations). In pure stands, growth of HR plants from AB and SK was similar to that of HS plants, regardless of mutation; conversely, MB2-HR plants (Trp574Leu) developed more slowly and were taller than MB2-HS plants. Final dry weight of HR plants in pure stands was similar across all six populations, whereas that for HS plants in pure stands and HR–HS plants in mixed stands (50–50%) varied with population. Results for AB and SK populations suggest little impact of either ALS mutation on kochia growth, whereas those for MB lines would suggest an unidentified factor (or factors) affecting the HS, HR, or both biotypes. The variable response within and between lines, and across HS biotypes highlights the importance of including populations of various origins and multiple susceptible controls in HR biotype studies.

Confirmation of Glyphosate-Resistant Horseweed (Conyza canadensis) in Montana Cereal Production and Response to POST Herbicides

2017 ◽  
Vol 31 (6) ◽  
pp. 799-810 ◽  
Author(s):  
Vipan Kumar ◽  
Prashant Jha ◽  
Amit J. Jhala
Keyword(s):  
Great Plains ◽  
Dose Response ◽  
Best Management Practices ◽  
Management Practices ◽  
Dry Weight ◽  
Shoot Dry Weight ◽  
Greenhouse Study ◽  
Whole Plant ◽  
Cereal Production ◽  
Sites Of Action

In recent years, horseweed has become an increasing problem in Montana. To confirm and characterize the level of glyphosate resistance, seeds were collected from putative glyphosate-resistant (GR) horseweed (GR-MT) plants in a wheat–fallow field in McCone County, MT. Known GR (GR-NE) and glyphosate-susceptible (GS-NE) horseweed accessions from Lincoln, NE, were included for comparison in dose–response and shikimate accumulation studies. Whole-plant glyphosate dose–response experiments conducted at the early- (5- to 8-cm diameter) and late- (12- to 15-cm diameter) rosette stages of horseweed indicated that GR-MT accessions had a 2.5- to 4.0-fold level of resistance to glyphosate relative to the GS-NE accession, on the basis of shoot dry weight (GR50values). The level of resistance was 3.1- to 7.9-fold on the basis of visually assessed injury estimates (I50values). At the whole-plant level, about 2.1- to 4.5-fold higher shikimate accumulation was observed in the GS-NE accession compared with the GR-MT and GR-NE accessions over a 10-d period after glyphosate was applied at 1,260 g ae ha−1. In a separate greenhouse study, all three horseweed accessions were also screened with alternate POST herbicides registered for use in wheat–fallow rotations. The majority of the tested herbicides provided ≥90% injury at the field-use rates for all three horseweed accessions 3 wk after treatment. This is the first published report on the occurrence of GR horseweed in Montana cereal production. Increased awareness and adoption of best management practices, including the use of diversified (based on multiple sites of action) herbicide programs highlighted in this study, would aid in mitigating the further spread of GR horseweed in the cereal production fields of the U.S. Great Plains.

scholarly journals Cultural weed management practices shorten the critical weed-free period for soybean grown in the Northern Great Plains

Weed Science ◽  
2019 ◽  
pp. 1-13
Author(s):  
Jonathan D. Rosset ◽  
Robert H. Gulden
Keyword(s):  
Great Plains ◽  
Weed Management ◽  
Competitive Ability ◽  
Management Practices ◽  
Developmental Stages ◽  
Cultural Practices ◽  
Northern Great Plains ◽  
Herbicide Resistant ◽  
Soybean Cultivars ◽  
Rotational Crop

Abstract Soybean [Glycine max (L.) Merr.] has recently become a popular rotational crop in the Canadian Northern Great Plains where herbicide-resistant (HR) soybean cultivars have been widely adopted. Intense reliance on herbicides has contributed to the development of HR weeds in soybean and other crops. Cultural weed management practices reduce the need for herbicides and lower the selection pressure for HR weed biotypes by improving the competitiveness of the crop. The effects of two row spacings, three target densities, and three cultivars on the critical weed-free period (CWFP) in soybean were evaluated as three separate experiments in southern Manitoba. In the row-spacing experiment, soybean grown in narrow rows shortened the CWFP by up to three soybean developmental stages at site-years with increased weed pressure. In the target density experiment, low-density soybean stands lengthened the CWFP by one soybean developmental stage compared with higher-density soybean stands. The effect of soybean cultivar varied among locations, yet tended to be consistent within location over the 2-yr study, suggesting that competitive ability in these soybean cultivars was linked to edaphic and/or environmental factors. Generally, the cultivar with the shortest days to maturity, which also had the shortest stature, consistently had a longer CWFP. Each of these cultural practices were effective at reducing the need for in-crop herbicide applications.

scholarly journals Differential susceptibility of biotypes of conyza sumatrensis to Chlorimuron-ethyl herbicide

2014 ◽  
Vol 32 (2) ◽  
pp. 427-435 ◽  
Author(s):  
F.M. Santos ◽  
L. Vargas ◽  
P.J. Christoffoleti ◽  
D. Agostinetto ◽  
F. Mariani ◽  
...  
Keyword(s):  
Dose Response ◽  
Weed Management ◽  
Leaf Growth ◽  
Differential Susceptibility ◽  
Dry Weight ◽  
Response Curves ◽  
Shoot Dry Weight ◽  
Randomized Design ◽  
Chlorimuron Ethyl ◽  
Dose Response Curves

Horseweed (Conyza spp.) is an annual weed, infesting soybean crops in southern Brazil, with chlorimuron-ethyl being one of the most commonly used herbicides for its control. However, in recent soybean harvests, an unsatisfactory control of this weed using this herbicide was observed, generating suspicion regarding the selection of resistant biotypes. The objective of this study was to evaluate the susceptibility of horseweed biotypes to the herbicide chlorimuron-ethyl. Two experiments were conducted in a greenhouse; in the first one, the biotypes were selected selected, and the second experiment was arranged in a 5 x 5 factorial in a completely randomized design with four replications. The treatments used in the preparation of the dose response curves were doses of the herbicide chlorimuron-ethyl (0.0, 1.56, 3.13, 6.25, 12.5, and 25 g ha-1), applied on the five horseweed biotypes at the 3-4 leaf growth stage. The variables evaluated were visual control percentage and shoot dry weight, compared to the control without herbicide application, and plant acetolactate accumulation. It was concluded that there is a differential susceptibility among the biotypes at doses of less than 20 g ha-1 (dose response curves), which indicates low-level resistance. The practical consequences are the indications of chlorimuron-ethyl application at the maximum doses recomended and that the practice of rotating mechanisms of action must be used in the chemical weed management of these areas.

Sumatran Fleabane (Erigeron sumatrensis) Resistant to PSI-Inhibitor Herbicides and Physiological Responses to Paraquat

Weed Science ◽  
2021 ◽  
pp. 1-26
Author(s):  
Jéssica F. L. Leal ◽  
Amanda dos S. Souza ◽  
Junior Borella ◽  
André Lucas S. Araujo ◽  
Ana Claudia Langaro ◽  
...  
Keyword(s):  
Dose Response ◽  
Weed Management ◽  
Crop Production ◽  
Antioxidant Enzyme Activities ◽  
Multiple Resistance ◽  
Fast Recovery ◽  
Continuous Growth ◽  
Herbicide Resistant ◽  
Paraquat Resistance ◽  
Resistance To Herbicides

Abstract Herbicide-resistant weed management is one of the greatest agricultural challenges in crop production. Thus, the quick identification of resistant-herbicide weeds is extremely important for management. This study aimed to evaluate resistance to PSI-inhibitor herbicides (diquat) of Sumatran Fleabane [(Erigeron sumatrensis (Retz.) E.Walker)] and physiological response to paraquat application. The research was conducted with two E. sumatrensis biotypes, one susceptible and the other with multiple resistance to herbicides from five different modes of action (glyphosate, paraquat, diuron, saflufenacil, and 2,4-D). A dose-response assay was carried out to evaluate herbicide resistance to diquat in paraquat-resistant E. sumatrensis biotype. The enzymatic activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), hydrogen peroxide (H2O2) content, and chlorophyll a fluorescence were measured in both biotypes after paraquat (400 g ai ha−1) application. The dose-response assay confirmed resistance of E. sumatrensis to diquat with resistance factor levels of 26-fold and 6-fold for LD50 and GR50 values, respectively, compared with the susceptible biotype. The accumulation of H2O2 occurred faster in the paraquat-susceptible biotype than in the resistant ones. Paraquat treatment caused an increase in SOD and APX activity in the susceptible biotype, but antioxidant enzyme activities were unaffected by paraquat in the resistant one at 5 hours after application (HAA). Chlorophyll a fluorescence increased along the first 4 HAA in both resistant and susceptible biotypes. However, at 24 HAA the resistant biotype showed a decline in fluorescence close to untreated plants while susceptible one died, which can be used to diagnose paraquat resistance at 24 HAA. There is confirmed resistance to diquat in a paraquat-resistant E. sumatrensis biotype. The paraquat-resistant biotype does not induce antioxidative enzymes, as a possible mechanism of resistance to paraquat, but shows a fast recovery of photosynthesis and continuous growth when subjected to paraquat, while the paraquat-susceptible biotype does not survive.

Weed Problems in Uruguayan Agriculture: Evolution and Current Situation

2021 ◽  
Vol 32 (5) ◽  
pp. 203-207
Author(s):  
M. Alejandro Garcia ◽  
Lucia V. Meneses ◽  
Tiago Edu Kaspary
Keyword(s):  
Weed Management ◽  
Agricultural Production ◽  
Production Systems ◽  
Integrated Weed Management ◽  
Zero Tillage ◽  
Weed Species ◽  
Management Tools ◽  
Herbicide Resistant ◽  
Species Frequencies ◽  
Agricultural Production Systems

Uruguayan agriculture has undergone dramatic changes in the last 50 years driven by the adoption of new agricultural production systems that incorporate zero tillage and herbicide resistant crops. This has resulted in a shift in weed species frequencies and the dispersion of introduced herbicide resistant weed populations. Finally, integrated weed management tools are being developed by research and extension services to manage herbicide-resistant (HR) weeds better and to reduce environmental impact of herbicides.

Effect of weed management on weeds, and on the nodulation, nitrogenase activity, growth and yield of pea (Pisum sativum)

2006 ◽  
Vol 54 (4) ◽  
pp. 469-485 ◽  
Author(s):  
G. Singh ◽  
D. Wright
Keyword(s):  
Pisum Sativum ◽  
Nitrogen Content ◽  
Weed Management ◽  
Plant Biomass ◽  
Nitrogenase Activity ◽  
Strong Relationship ◽  
Dry Weight ◽  
Growth And Yield ◽  
N Content ◽  
Shoot Dry Weight

Effects of one pre-emergence herbicide (terbutryn/terbuthylazine) and one post-emergence herbicide (bentazone) along with unweeded and hand-weeded controls on weeds and on the nodulation, nitrogenase activity, nitrogen content, growth and yield of pea (Pisum sativum) were studied. Terbutryn/terbuthylazine was applied pre-emergence @ 1.40, 2.80 and 5.60 kg/hawhereas bentazone was sprayed 6 weeks after sowing @ 1.44, 2.88 and 5.76 kg/h. Terbutryn/terbuthylazine controlled all the weeds very effectively, whereas bentazone did not control some weeds such as Polygonum aviculare, Poa annua and Elymus repens. The herbicides decreased the number of nodules, the dry weight of nodules, the nitrogenase activity, the shoot dry weight, the nitrogen content in the straw and seeds, and the seed yield of peas, the effects generally being higher at higher rates of application. The adverse effects of herbicides on these parameters might be due to their effects on plant growth, as both the herbicides are known to adversely affect photosynthesis. Nitrogenase activity did not correlate well with plant-N content or shoot dry weight. However, there was a strong relationship between plant biomass and plant-N content, which suggests that researchers can rely on these parameters for studying the effects of treatments on nitrogen fixation, rather than measuring nitrogenase activity.

Planting Date and Preplant Weed Management Influence Yield, Water Use, and Weed Seed Production in Herbicide-Free Forage Barley

2008 ◽  
Vol 22 (3) ◽  
pp. 486-492 ◽  
Author(s):  
Andrew W. Lenssen
Keyword(s):  
Seed Production ◽  
Water Use ◽  
Great Plains ◽  
Weed Management ◽  
Planting Date ◽  
Management Systems ◽  
Northern Great Plains ◽  
Zero Tillage ◽  
Weed Seed ◽  
Early Planting

In the semiarid northern Great Plains, the adoption of zero tillage improves soil water conservation, allowing for increased crop intensification and diversification. Zero-tillage crop production relies heavily on herbicides for weed management, particularly the herbicide glyphosate, increasing selection pressure for herbicide-resistant weeds. Barley is well adapted to the northern Great Plains, and may be a suitable herbicide-free forage crop in zero-tillage systems. A 2-yr field study was conducted to determine if planting date influenced crop and weed biomass, water use (WU), and water-use efficiency (WUE) of barley and weed seed production in three preplant weed management systems: (1) conventional preplant tillage with a field cultivator (TILL); (2) zero tillage with preemergence glyphosate application (ZTPRE); and (3) zero tillage without preemergence glyphosate (ZT). None of the systems included an in-crop herbicide. Planting dates were mid-April (early), late May (mid), and mid-June (delayed). Early planting of ZT barley resulted in excellent forage yields (7,228 kg/ha), similar to those from TILL and ZTPRE. Early planting resulted in a small accumulation of weed biomass, averaging 76 kg/ha, and no weed seed production regardless of preplant weed management system. Early planting resulted in higher WU than delayed planting, averaging 289 and 221 mm, respectively, across management systems and years. The WUE of crop and total biomass did not differ among preplant weed management systems at harvest from the early planting date. Delayed planting resulted in decreased forage yield with high amounts of weed biomass and seed production, especially in ZT. A pre-emergence glyphosate application was not necessary for early-planted ZT forage barley. Early planting of herbicide-free barley for forage can be an excellent addition to northern Great Plains cropping systems as part of a multitactic approach for improved weed and water management.

A Waterhemp (Amaranthus tuberculatus) Population Resistant to 2,4-D

Weed Science ◽  
2012 ◽  
Vol 60 (3) ◽  
pp. 379-384 ◽  
Author(s):  
Mark L. Bernards ◽  
Roberto J. Crespo ◽  
Greg R. Kruger ◽  
Roch Gaussoin ◽  
Patrick J. Tranel
Keyword(s):  
Dose Response ◽  
Dry Weight ◽  
Population Based ◽  
Susceptible Population ◽  
Herbicide Resistant ◽  
Synthetic Auxins ◽  
Resistant Population ◽  
Amaranthus Tuberculatus ◽  
Susceptible Populations ◽  
Dose Response Study

A waterhemp population from a native-grass seed production field in Nebraska was no longer effectively controlled by 2,4-D. Seed was collected from the site, and dose-response studies were conducted to determine if this population was herbicide resistant. In the greenhouse, plants from the putative resistant and a susceptible waterhemp population were treated with 0, 18, 35, 70, 140, 280, 560, 1,120, or 2,240 g ae ha−12,4-D. Visual injury estimates (I) were made 28 d after treatment (DAT), and plants were harvested and dry weights (GR) measured. The putative resistant population was approximately 10-fold more resistant to 2,4-D (R:S ratio) than the susceptible population based on both I50(50% visual injury) and GR50(50% reduction in dry weight) values. The R:S ratio increased to 19 and 111 as the data were extrapolated to I90and GR90estimates, respectively. GR50doses of 995 g ha−1for the resistant and 109 g ha−1for the susceptible populations were estimated. A field dose-response study was conducted at the suspected resistant site with 2,4-D doses of 0, 140, 280, 560, 1,120, 2,240, 4,480, 8,960, 17,920, and 35,840 g ha−1. At 28 DAT, visual injury estimates were 44% in plots treated with 35,840 g ha−1. Some plants treated with the highest rate recovered and produced seed. Plants from the resistant and susceptible populations were also treated with 0, 9, 18, 35, 70, 140, 280, 560, or 1,120 g ae ha−1dicamba in greenhouse bioassays. The 2,4-D resistant population was threefold less sensitive to dicamba based on I50estimates but less than twofold less sensitive based on GR50estimates. The synthetic auxins are the sixth mechanism-of-action herbicide group to which waterhemp has evolved resistance.

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