Paraquat resistance in horseweed (Conyza canadensis) and Virginia pepperweed (Lepidium virginicum) from Essex County, Ontario

Weed Science ◽  
1998 ◽  
Vol 46 (2) ◽  
pp. 200-204 ◽  
Author(s):  
Alida Smisek ◽  
Colleen Doucet ◽  
Martha Jones ◽  
Susan Weaver
Keyword(s):  
Dose Response ◽  
Dry Weight ◽  
Repeated Exposure ◽  
Conyza Canadensis ◽  
Essex County ◽  
Shoot Dry Weight ◽  
Paraquat Resistance ◽  
Resistant Population ◽  
Susceptible Populations ◽  
Fruit Orchards

Populations of horseweed and Virginia pepperweed resistant to the herbicide paraquat were found in several fruit orchards in Essex County, Ontario, Canada, where paraquat had been applied four to five times per year for at least 10 yr. Dose–response experiments were conducted in the greenhouse for each species, using 2-to 4-mo-old plants from populations that had received repeated exposure to paraquat and those that had not. The paraquat dose that reduced shoot dry weight by 50% (ED50) was estimated for each population. Resistant populations of horseweed had ED50 values 25 to 35 times higher than susceptible populations. A resistant population of Virginia pepperweed had an ED50 10 times higher than susceptible populations.

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.

Response of paraquat-resistant and -susceptible horseweed (Conyza canadensis) to diquat, linuron, and oxyfluorfen

Weed Science ◽  
2004 ◽  
Vol 52 (4) ◽  
pp. 549-553 ◽  
Author(s):  
Susan Weaver ◽  
Michael Downs ◽  
Brandi Neufeld
Keyword(s):  
Dry Weight ◽  
Conyza Canadensis ◽  
Modes Of Action ◽  
Shoot Dry Weight ◽  
Age Dependent ◽  
Winter Annual ◽  
Susceptible Populations

Horseweed is a winter annual weed that has evolved resistance to multiple herbicide modes of action in 11 countries worldwide. A paraquat-resistant horseweed population in an Ontario orchard that was being managed by a rotation of herbicides began to show increased tolerance to the herbicide linuron. Experiments were conducted in the greenhouse to compare the response of this population and several paraquat-susceptible populations to linuron, diquat, and oxyfluorfen. Plants were sprayed with a range of doses of each herbicide when they were from 5 to 10 wk old, and the ED50, or dose at which shoot dry weight was reduced by 50%, was estimated. There was a sevenfold difference in the ED50values of the paraquat-resistant and -susceptible populations in response to diquat and a threefold difference in response to linuron. The response to oxyfluorfen was age dependent. The ratio of resistance to susceptible ED50values was estimated as 57 for 5-wk-old plants and 11 for 8-wk-old plants in response to oxyfluorfen. Ten-week-old plants from both populations showed no response to oxyfluorfen at rates up to 4.8 kg ai ha−1.

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.

The relative competitiveness of atrazine susceptible and resistant populations of Chenopodium album and C. strictum

1981 ◽  
Vol 59 (5) ◽  
pp. 689-693 ◽  
Author(s):  
S. I. Warwick ◽  
L. Black
Keyword(s):  
Biomass Production ◽  
Aboveground Biomass ◽  
Competitive Ability ◽  
Chenopodium Album ◽  
Dry Weight ◽  
Replacement Series ◽  
Susceptible Population ◽  
Resistant Population ◽  
Reproductive Biomass ◽  
Susceptible Populations

The total aboveground biomass and reproductive dry weight of one atrazine resistant and one susceptible population from southern Ontario of each of two species of Chenopodium, C. album and C. strictum, were compared. The comparison was made between plants grown under both noncompetitive and competitive conditions. Results from a spaced noncompetitive trial provided evidence for: (1) greater total and reproductive biomass production and earlier flowering of resistant and susceptible populations of C. album as compared with both populations of C. strictum, (2) greater aboveground total and reproductive biomass production of the susceptible population of C. album as compared with the resistant population, and (3) greater total aboveground biomass production (but similar reproductive biomass) of the susceptible population of C. strictum as compared with the resistant population. Results from the competition trials (i.e., plants grown in a de Wit replacement series), provided evidence for inter- and intra-specific differences in competitive ability: (1) the susceptible population of C. album was found to be more competitive than the susceptible population of C. strictum, (2) the susceptible population of C. album was a superior competitor to the resistant population, and (3) the resistant and susceptible populations of C. strictum appeared to be equally competitive.

scholarly journals Dose-response curves of Lolium multiflorum biotypes resistant and susceptible to clethodim

2013 ◽  
Vol 31 (4) ◽  
pp. 887-892 ◽  
Author(s):  
L. Vargas ◽  
D.S. Fraga ◽  
D. Agostinetto ◽  
F. Mariani ◽  
T.V. Duarte ◽  
...  
Keyword(s):  
Dose Response ◽  
Chemical Control ◽  
Lolium Multiflorum ◽  
Dry Weight ◽  
Rio Grande Do Sul ◽  
Response Curves ◽  
Main Method ◽  
Shoot Dry Weight ◽  
Repeated Use ◽  
Dose Response Curves

Chemical control with herbicides, especially glyphosate, is the main method used to control ryegrass. However, the repeated use of glyphosate has selected resistant ryegrass biotypes. Thus, the ACCase inhibitor herbicides have become the main alternative to control glyphosate-resistant biotypes, being widely used by farmers in Rio Grande do Sul. Repeated use of ACCase inhibitors, in turn, have selected ryegrass biotypes resistant to this herbicide mechanism. Thus, the objective of this study was to evaluate the response of ryegrass biotypes to different clethodim rates by dose-response curves. Increasing doses (0, 12, 24, 48, 72, 96, 144 and 192 g a.i. ha-1) of the herbicide clethodim were applied at the 3-4 ryegrass leaf stage. The variables control at 14 and 28 days after treatment (DAT) and shoot dry weight were evaluated. The data were fitted by nonlinear regression log-logistic and C50 and GR50 were calculated based on the equation. The resistance factor was obtained by the ratio of C50 or GR50 of the resistant biotype by matching the susceptible biotype. Based on the equation parameters, the doses of GR50 64.7 and 234.5 g a.i. ha-1 clethodim and C50 11.2 and 172.1 g a.i. ha-1 clethodim were obtained, at 28 DAT for the susceptible and resistant biotypes, respectively. The ryegrass biotype denominated Cotril is resistant to clethodim, being controlled with a dose 15.3 times greater than that of the susceptible biotype, and a 50% reduction of this biotype occurs with a dose 3.62 times higher than that of the susceptible one.

scholarly journals Wheat Density Alters but Does Not Repress the Expression of a Fluroxypyr-Resistant Kochia (Bassia scoparia) Phenotype

Agronomy ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 2160
Author(s):  
Charles M. Geddes ◽  
Michael T. Kimmins
Keyword(s):  
Dose Response ◽  
Triticum Aestivum L ◽  
Controlled Environment ◽  
Dose Response Relationship ◽  
Plant Survival ◽  
Herbicide Resistant ◽  
Resistant Population ◽  
Plant Interference ◽  
Susceptible Populations ◽  
Relationship Of

Dose-response experiments for confirmation of herbicide-resistant weeds are almost always conducted using weed monocultures, thereby ignoring the interaction of interspecific plant interference with herbicide efficacy. Controlled-environment dose-response bioassays were conducted using three kochia [Bassia scoparia (L.) A.J. Scott] populations with four spring wheat (Triticum aestivum L.) densities (0, 200, 400, and 600 plants m−2) to determine how increasing intensity of interspecific plant interference altered the fluroxypyr dose-response relationship of resistant and susceptible kochia. The resistant population exhibited 10.8-, 15.0-, 7.0-, and 8.1-fold resistance to fluroxypyr in the absence of crop interference based on plant survival, biomass fresh weight, and visible control at two and four weeks after application, respectively. Increased wheat densities suppressed fluroxypyr-resistant kochia the greatest, resulting in a linear reduction in the fluroxypyr rate causing 50% plant mortality (LD50) and visible control (ED50) for the resistant but not the susceptible populations. This reduced the expression of fluroxypyr resistance based on kochia plant survival (from 10.8- to 4.3-fold resistance) and visible control (from 8.1- to 4.6-fold resistance) as wheat density increased from 0 to 600 plants m−2. Therefore, enhanced interspecific plant interference caused by increased wheat densities altered but did not repress the expression of fluroxypyr resistance in kochia.

Response of Giant Reed (Arundo donax) to Asulam and Trifloxysulfuron

2012 ◽  
Vol 26 (1) ◽  
pp. 71-76 ◽  
Author(s):  
Dennis C. Odero ◽  
Robert A. Gilbert
Keyword(s):  
Dose Response ◽  
Dry Weight ◽  
South Florida ◽  
Giant Reed ◽  
Bioenergy Crop ◽  
Invasive Potential ◽  
Complete Control ◽  
Production Region ◽  
Shoot Dry Weight ◽  
Research And Education

Giant reed has been proposed as a bioenergy crop in the sugarcane production region of south Florida, where it has a high invasive potential. In an effort to limit future invasion of giant reed escapes in sugarcane, currently labeled sugarcane herbicides asulam and trifloxysulfuron were evaluated for its management. Greenhouse and field dose–response studies were conducted at the Everglades Research and Education Center in Belle Glade, FL, between 2010 and 2011. Herbicides were applied at rates ranging from 0.46 to 7.4 kg ha−1asulam and 2 to 32 g ha−1trifloxysulfuron, which represent 0.125× to 2× sugarcane labeled use rates, respectively. In the greenhouse, asulam and trifloxysulfuron reduced giant reed relative shoot dry weight by a maximum of 50% at 21 d after treatment (DAT). The probability of giant reed resprouting 35 d following herbicide treatment was greater for trifloxysulfuron when compared with asulam. In the field, it was predicted that a maximum of 69 and 55% giant reed control occurred with application of asulam and trifloxysulfuron, respectively, at 14 DAT. Relative shoot dry weight of giant reed treated with asulam and trifloxysulfuron was reduced by a maximum of 43% at 42 DAT. Application of asulam and trifloxysulfuron did not provide complete control of giant reed at twice the labeled sugarcane use rate, indicating that control of established giant reed in sugarcane with currently available herbicides would not be an option.

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.

Assessing Herbicide Phytotoxicity with Covariance Analysis

1990 ◽  
Vol 4 (4) ◽  
pp. 828-832 ◽  
Author(s):  
S. Kent Harrison ◽  
Emilie E. Regnier
Keyword(s):  
Dose Response ◽  
Treatment Effects ◽  
Dry Weight ◽  
Leaf Length ◽  
Covariance Analysis ◽  
Standard Analysis ◽  
Response Variable ◽  
Shoot Dry Weight ◽  
Statistical Precision ◽  
Corn Seedling

Greenhouse experiments were conducted to determine the statistical precision of estimating herbicide dose-response treatment effects by covariance analysis (ANOCOVA) relative to standard analysis of variance (ANOVA). Analyses of corn seedling response to the translocated herbicides fluazifop-P, sethoxydim, and quizalofop at 10 to 60 g ai ha-1 indicated that treatment effects were estimated with 26 to 116% greater precision by ANOCOVA than ANOVA. Covariance analyses of treatment effects for corn response to the contact herbicides paraquat, acifluorfen, and lactofen at 50 to 300 g ai ha-1 gave 8 to 13% greater precision than ANOVA. Gains in precision by ANOCOVA for all experiments were generally greatest when shoot dry weight was analyzed as the response variable and pretreatment fifth leaf length served as the covariate.

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.

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