The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Hans E. Hummel - One of the best experts on this subject based on the ideXlab platform.
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gas chromatography mass spectrometry analysis of the herbicide Clopyralid in differentially cultivated soils
Environmental Toxicology and Chemistry, 1996Co-Authors: Stefan Schütz, B Weisbecker, Hans E. HummelAbstract:The herbicide Clopyralid offers a high selectivity in thistle control using low application rates. Contradictory results in soil leaching experiments using this herbicide indicate the need for a reliable procedure for trace analysis of Clopyralid. The problem of poor extraction efficiency from soil that is rich in humic substances was solved by ultrasound-enhanced alkaline extraction. Analysis of the extract was performed by gas chromatography-mass spectrometry after derivatization with pentafluorobenzylbromide in an ultrasound-enhanced phase-transfer catalytic reaction. Tetrabutylammoniumbromide served as a phase-transfer catalyst. For improving analytical reliability, 2,5-dichlorobenzoic acid was used as an internal standard. The achieved detection (1 μg/kg = 1 ppb) and quantification (10 μg/kg) limits of Clopyralid in soil were appropriate for determining the degradation behavior in herbicide-treated soils. The half-life of Clopyralid in two differentially cultivated soils was determined in laboratory trials. Uncultivated soil that was rich in humic acids showed a higher half-life than cultivated soil.
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Analysis of the herbicide Clopyralid in cultivated soils
Journal of Chromatography A, 1996Co-Authors: Stefan Schütz, H. Vedder, Rolf-alexander Düring, Bernhard Weissbecker, Hans E. HummelAbstract:Abstract Clopyralid is a broad-spectrum herbicide for thistle control in vegetable cultivation. Its application rate amounts to 0.2 kg/ha. However, contradictory results in soil leaching experiments require a reliable routine procedure for trace analysis of Clopyralid in soil. Previously reported methods for Clopyralid analysis in several matrices either proved to be insufficient for analysis in soil and leaching water or require the use of critical chemicals and are too complicated for routine analysis. The problem of poor extraction recovery of Clopyralid from soil rich in humic acids was solved by phase transfer extraction of soil samples. Analysis of the extract was performed by GC-MS directly after the extractive phase transfer catalytic reaction. Tetrabutylammoniumhydroxide served as a phase transfer catalyst. For improving analytical reliability, 2.5-dichlorobenzoic acid was used as an internal standard. Detection limit (1 μg/kg=1 ppb) and quantification limit (10 μg/kg) of Clopyralid in soil were found to be appropriate for determining the behaviour in herbicide treated soils. The leaching and disappearance of Clopyralid in two differently tilled soils were determined in field trials.
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Gas chromatography‐mass spectrometry analysis of the herbicide Clopyralid in differentially cultivated soils
Environmental Toxicology and Chemistry, 1996Co-Authors: Stefan Schütz, Bernhard Weissbecker, Hans E. HummelAbstract:The herbicide Clopyralid offers a high selectivity in thistle control using low application rates. Contradictory results in soil leaching experiments using this herbicide indicate the need for a reliable procedure for trace analysis of Clopyralid. The problem of poor extraction efficiency from soil that is rich in humic substances was solved by ultrasound-enhanced alkaline extraction. Analysis of the extract was performed by gas chromatography-mass spectrometry after derivatization with pentafluorobenzylbromide in an ultrasound-enhanced phase-transfer catalytic reaction. Tetrabutylammoniumbromide served as a phase-transfer catalyst. For improving analytical reliability, 2,5-dichlorobenzoic acid was used as an internal standard. The achieved detection (1 μg/kg = 1 ppb) and quantification (10 μg/kg) limits of Clopyralid in soil were appropriate for determining the degradation behavior in herbicide-treated soils. The half-life of Clopyralid in two differentially cultivated soils was determined in laboratory trials. Uncultivated soil that was rich in humic acids showed a higher half-life than cultivated soil.
Tracy M Sterling - One of the best experts on this subject based on the ideXlab platform.
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Clopyralid uptake translocation metabolism and ethylene induction in picloram resistant yellow starthistle centaurea solstitialis l
Pesticide Biochemistry and Physiology, 2001Co-Authors: Juan M Valenzuelavalenzuela, Norman K Lownds, Tracy M SterlingAbstract:Resistance to the auxinic herbicide picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) has been reported in a population of yellow starthistle (Centaurea solstitialis L.) growing in a nonarable pasture in Dayton, Washington. In addition, these plants are cross-resistant to Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) and other auxinic herbicides. To understand the mechanism of cross-resistance to Clopyralid, uptake, translocation, and metabolism of Clopyralid were compared between the picloram-resistant (R) and the -susceptible (S) accessions of this weed species. Radiolabeled Clopyralid was applied to individual leaves of rosette-stage plants under controlled environmental conditions. Both accessions absorbed about 75% of the total applied within the first 2 h following treatment. Uptake increased linearly with Clopyralid concentration, but was not different in accessions in the range of concentrations studied. Also, there was no difference between accessions in Clopyralid partitioning into epicuticular wax. About 50% of the total absorbed radioactivity moved out of the treated leaf toward both upper and lower shoots 96 h following treatment in both accessions. Within 2 h of treatment, Clopyralid was converted by R and S plants to similar quantities of metabolites. After 96 h, R plants metabolized more Clopyralid than S plants, suggesting a possible role of herbicide metabolism in cross-resistance. However, the Clopyralid-induced symptoms of ethylene production and epinasty appeared in S plants within 5 h, implying that mechanism(s) of cross-resistance involves process(es) other than metabolism.
Norman K Lownds - One of the best experts on this subject based on the ideXlab platform.
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Inheritance of Resistance to Clopyralid and Picloram in Yellow Starthistle (Centaurea solstitialis L.) Is Controlled by a Single Nuclear Recessive Gene
2015Co-Authors: R. P. Sabba, Norman K Lownds, I. M. Ray, T. M. SterlingAbstract:The noxious weed yellow starthistle (Centaurea solstitialis L.) can be controlled effectively at the seedling stage with foliar application of the auxinic herbicides picloram or Clopyralid. Although resistance to these herbicides is rare, a yellow starthistle biotype resistant to picloram and cross-resistant to Clopyralid was observed in 1989 near Dayton, WA, in a pasture that had been subjected to intensive picloram selective pressure. Our objective was to determine the mode of inheritance for this resistance trait. Transmission of the resistant phenotype was monitored in reciprocal F1 crosses between susceptible (SCI) and resistant (RDW) plants, their testcross and pseudo-F2 progeny. Progeny from all crosses, as well as RDW and SCI seedlings of original populations, were sprayed with picloram or Clopyralid to distinguish between susceptible and resistant individuals. All F1 progeny wer
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Clopyralid uptake translocation metabolism and ethylene induction in picloram resistant yellow starthistle centaurea solstitialis l
Pesticide Biochemistry and Physiology, 2001Co-Authors: Juan M Valenzuelavalenzuela, Norman K Lownds, Tracy M SterlingAbstract:Resistance to the auxinic herbicide picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) has been reported in a population of yellow starthistle (Centaurea solstitialis L.) growing in a nonarable pasture in Dayton, Washington. In addition, these plants are cross-resistant to Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) and other auxinic herbicides. To understand the mechanism of cross-resistance to Clopyralid, uptake, translocation, and metabolism of Clopyralid were compared between the picloram-resistant (R) and the -susceptible (S) accessions of this weed species. Radiolabeled Clopyralid was applied to individual leaves of rosette-stage plants under controlled environmental conditions. Both accessions absorbed about 75% of the total applied within the first 2 h following treatment. Uptake increased linearly with Clopyralid concentration, but was not different in accessions in the range of concentrations studied. Also, there was no difference between accessions in Clopyralid partitioning into epicuticular wax. About 50% of the total absorbed radioactivity moved out of the treated leaf toward both upper and lower shoots 96 h following treatment in both accessions. Within 2 h of treatment, Clopyralid was converted by R and S plants to similar quantities of metabolites. After 96 h, R plants metabolized more Clopyralid than S plants, suggesting a possible role of herbicide metabolism in cross-resistance. However, the Clopyralid-induced symptoms of ethylene production and epinasty appeared in S plants within 5 h, implying that mechanism(s) of cross-resistance involves process(es) other than metabolism.
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Clopyralid Uptake, Translocation, and Ethylene Production in Resistant and Susceptible Yellow Starthistle (Centaurea solstitialis) Plants
HortScience, 1996Co-Authors: Juan M. Valenzuela-valenzuela, Norman K LowndsAbstract:Resistance to the auxin-like herbicide picloram has been reported in a yellow starthistle population growing in Washington. In addition, this population is cross resistant to Clopyralid, another auxin-like herbicide. To understand the mechanism of resistance to Clopyralid, studies were was conducted to determine uptake and translocation and to characterize Clopyralid-induced ethylene production in the susceptible (S) and resistant (R) biotypes. R and S yellow starthistle plants were grown under ambient greenhouse conditions until full rosette stage and then transferred to a growth chamber (14-hour photoperiod, 25°C, 200 mol·m–2·s–1) 48 hours before treatment. Radiolabel solutions were prepared from 12C and 14C-Clopyralid. Each treatment in the uptake experiment contained 0.009 Ci (20,000 dpm) and in the translocation experiment 0.225 Ci (500,000 dpm). Clopyralid 11.7 mm (420 g a.e./ha) solutions were applied as six 0.5-L droplets to the adaxial surface of completely expanded leaves using a microsyringe. Radioactivity was quantified by Liquid Scintillation Spectrometry. Uptake was determined at specified times after treatment. Almost all Clopyralid uptake occurred within the first 2 hours, with no significant differences between the two biotypes. The amount of picloram translocated was 2.4%, 40.2%, and 50.7% of that absorbed at 2, 24, and 96 hours after treatment, respectively, but was not different between biotypes. Clopyralid induced about ten times greater ethylene production in S than in R. Ethylene production was followed by epinasty and chlorosis but appears to play only a small role in the resistance mechanism.
Stefan Schütz - One of the best experts on this subject based on the ideXlab platform.
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gas chromatography mass spectrometry analysis of the herbicide Clopyralid in differentially cultivated soils
Environmental Toxicology and Chemistry, 1996Co-Authors: Stefan Schütz, B Weisbecker, Hans E. HummelAbstract:The herbicide Clopyralid offers a high selectivity in thistle control using low application rates. Contradictory results in soil leaching experiments using this herbicide indicate the need for a reliable procedure for trace analysis of Clopyralid. The problem of poor extraction efficiency from soil that is rich in humic substances was solved by ultrasound-enhanced alkaline extraction. Analysis of the extract was performed by gas chromatography-mass spectrometry after derivatization with pentafluorobenzylbromide in an ultrasound-enhanced phase-transfer catalytic reaction. Tetrabutylammoniumbromide served as a phase-transfer catalyst. For improving analytical reliability, 2,5-dichlorobenzoic acid was used as an internal standard. The achieved detection (1 μg/kg = 1 ppb) and quantification (10 μg/kg) limits of Clopyralid in soil were appropriate for determining the degradation behavior in herbicide-treated soils. The half-life of Clopyralid in two differentially cultivated soils was determined in laboratory trials. Uncultivated soil that was rich in humic acids showed a higher half-life than cultivated soil.
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Analysis of the herbicide Clopyralid in cultivated soils
Journal of Chromatography A, 1996Co-Authors: Stefan Schütz, H. Vedder, Rolf-alexander Düring, Bernhard Weissbecker, Hans E. HummelAbstract:Abstract Clopyralid is a broad-spectrum herbicide for thistle control in vegetable cultivation. Its application rate amounts to 0.2 kg/ha. However, contradictory results in soil leaching experiments require a reliable routine procedure for trace analysis of Clopyralid in soil. Previously reported methods for Clopyralid analysis in several matrices either proved to be insufficient for analysis in soil and leaching water or require the use of critical chemicals and are too complicated for routine analysis. The problem of poor extraction recovery of Clopyralid from soil rich in humic acids was solved by phase transfer extraction of soil samples. Analysis of the extract was performed by GC-MS directly after the extractive phase transfer catalytic reaction. Tetrabutylammoniumhydroxide served as a phase transfer catalyst. For improving analytical reliability, 2.5-dichlorobenzoic acid was used as an internal standard. Detection limit (1 μg/kg=1 ppb) and quantification limit (10 μg/kg) of Clopyralid in soil were found to be appropriate for determining the behaviour in herbicide treated soils. The leaching and disappearance of Clopyralid in two differently tilled soils were determined in field trials.
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Gas chromatography‐mass spectrometry analysis of the herbicide Clopyralid in differentially cultivated soils
Environmental Toxicology and Chemistry, 1996Co-Authors: Stefan Schütz, Bernhard Weissbecker, Hans E. HummelAbstract:The herbicide Clopyralid offers a high selectivity in thistle control using low application rates. Contradictory results in soil leaching experiments using this herbicide indicate the need for a reliable procedure for trace analysis of Clopyralid. The problem of poor extraction efficiency from soil that is rich in humic substances was solved by ultrasound-enhanced alkaline extraction. Analysis of the extract was performed by gas chromatography-mass spectrometry after derivatization with pentafluorobenzylbromide in an ultrasound-enhanced phase-transfer catalytic reaction. Tetrabutylammoniumbromide served as a phase-transfer catalyst. For improving analytical reliability, 2,5-dichlorobenzoic acid was used as an internal standard. The achieved detection (1 μg/kg = 1 ppb) and quantification (10 μg/kg) limits of Clopyralid in soil were appropriate for determining the degradation behavior in herbicide-treated soils. The half-life of Clopyralid in two differentially cultivated soils was determined in laboratory trials. Uncultivated soil that was rich in humic acids showed a higher half-life than cultivated soil.
Robert G. Wilson - One of the best experts on this subject based on the ideXlab platform.
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canada thistle cirsium arvense control with aminopyralid in range pasture and noncrop areas
Weed Technology, 2007Co-Authors: Stephen F. Enloe, Robert G. Wilson, Scott J Nissen, Vanelle F Peterson, Phil Westra, George Beck, Michael Moechnig, Robert A Masters, Mary B. HalstvedtAbstract:Canada thistle is a serious weed of many crop, rangeland, pasture, and natural areas throughout North America. Aminopyralid is a new pyridine carboxylic acid herbicide that has activity on Canada thistle at lower use rates than current standard treatments. The objectives of this study were to compare aminopyralid efficacy, rates, and application timing with several commercial standards for Canada thistle control. Studies were conducted across the Great Plains at ten locations, which encompassed a wide range of environments. Aminopyralid provided Canada thistle control comparable to picloram, picloram + 2,4-D amine, and Clopyralid and better control than Clopyralid + 2,4-D amine, dicamba, dicamba + 2,4-D amine and dicamba + diflufenzopyr. Canada thistle control was similar when aminopyralid was applied between 0.08 and 0.11 kg ai/ha and application timing (spring bolting vs. fall rosette/regrowth) did not strongly influence control 1 yr after treatment (YAT). Aminopyralid provided effective Canada thistle control at lower use rates than current commercial standards and might be useful in areas where herbicides such as picloram and Clopyralid are not recommended for use. Nomenclature: Aminopyralid; Clopyralid; dicamba; diflufenzopyr; picloram; 2,4-D amine; Canada thistle, Cirsium arvense L. Scop. CIRAR.
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Response of sugarbeet, common sunflower, and common cocklebur to Clopyralid or desmidipham plus phenmedipham
Journal of Sugarbeet Research, 1995Co-Authors: Robert G. WilsonAbstract:A three-year experiment was conducted near Scottsbluff, NE, to evaluate the selectivity of Clopyralid, desmedipham plus phenmedipham, and the combination for common sunflower and common cocklebur control in sugarbeet. Clopyralid provided 81 to 98% control of common sunflower and 95 to 98% control of common cocklebur while desmedipham plus phenmedipham provided poor control of both weeds. Combinations of Clopyralid plus desmedipham plus phenmedipham provided good control of both weeds but in some years the treatment increased sugarbeet injury over that observed when Clopyralid was applied alone. Common sunflower and common cocklebur at densities of 5 plants/9 m of crop row reduced sugarbeet root yield 31 and 28%, respectively. Clopyralid's efficacy on common sunflower and common cocklebur was reflected in sugarbeet root yields similar to those observed in a handweeded control.