scholarly journals Confirmation of S-metolachlor resistance in Palmer amaranth (Amaranthus palmeri)

2019 ◽  
Vol 33 (5) ◽  
pp. 720-726 ◽  
Author(s):  
Chad Brabham ◽  
Jason K. Norsworthy ◽  
Michael M. Houston ◽  
Vijay K Varanasi ◽  
Tom Barber
Keyword(s):  
Dose Response ◽  
Resistance Mechanism ◽  
Acetolactate Synthase ◽  
Chain Fatty Acid ◽  
Palmer Amaranth ◽  
Cross Resistance ◽  
Amaranthus Palmeri ◽  
Glutathione S Transferase ◽  
Long Chain Fatty Acid ◽  
Long Chain

AbstractS-Metolachlor is commonly used by soybean and cotton growers, especially with POST treatments for overlapping residuals, to obtain season-long control of glyphosate- and acetolactate synthase (ALS)–resistant Palmer amaranth. In Crittenden County, AR, reports of Palmer amaranth escapes following S-metolachlor treatment were first noted at field sites near Crawfordsville and Marion in 2016. Field and greenhouse experiments were conducted to confirm S-metolachlor resistance and to test for cross-resistance to other very-long-chain fatty acid (VLCFA)–inhibiting herbicides in Palmer amaranth accessions from Crawfordsville and Marion. Palmer amaranth control in the field (soil <3% organic matter) 14 d after treatment (DAT) was ≥94% with a 1× rate of acetochlor (1,472 g ai ha–1; emulsifiable concentrate formulation) and dimethenamid-P (631 g ai ha–1). However, S-metolachlor at 1,064 g ai ha–1 provided only 76% control, which was not significantly different from the 1/2× and 1/4× rates of dimethenamid-P and acetochlor (66% to 85%). In the greenhouse, Palmer amaranth accessions from Marion and Crawfordsville were 9.8 and 8.3 times more resistant to S-metolachlor compared with two susceptible accessions based on LD50 values obtained from dose–response experiments. Two-thirds and 1.5 times S-metolachlor at 1,064 g ha–1 were the estimated rates required to obtain 90% mortality of the Crawfordsville and Marion accessions, respectively. Data collected from the field and greenhouse confirm that these accessions have evolved a low level of resistance to S-metolachlor. In an agar-based assay, the level of resistance in the Marion accession was significantly reduced in the presence of a glutathione S-transferase (GST) inhibitor, suggesting that GSTs are the probable resistance mechanism. With respect to other VLCFA-inhibiting herbicides, Marion and Crawfordsville accessions were not cross-resistant to acetochlor, dimethenamid-P, or pyroxasulfone. However, both accessions, based on LD50 values obtained from greenhouse dose–response experiments, exhibited reduced sensitivity (1.5- to 3.6-fold) to the tested VLCFA-inhibiting herbicides.

Control of Atrazine-Resistant Palmer Amaranth (Amaranthus palmeri) in Double-Crop Grain Sorghum

2019 ◽  
Vol 33 (1) ◽  
pp. 115-122
Author(s):  
Marshall M. Hay ◽  
Jeffrey J. Albers ◽  
J. Anita Dille ◽  
Dallas E. Peterson
Keyword(s):  
Cropping System ◽  
Grain Sorghum ◽  
Chain Fatty Acid ◽  
Palmer Amaranth ◽  
Amaranthus Palmeri ◽  
Long Chain Fatty Acid ◽  
Southern Plains ◽  
Weed Density ◽  
Herbicide Programs ◽  
Long Chain

AbstractDouble-crop grain sorghum after winter wheat harvest is a common cropping system in the southern plains region. Palmer amaranth is a troublesome weed in double-crop grain sorghum in Kansas. Populations resistant to various herbicides (e.g., atrazine, glyphosate, metsulfuron, pyrasulfotole) have made Palmer amaranth management even more difficult for producers. To evaluate control of atrazine-resistant and atrazine-susceptible Palmer amaranth in double-crop grain sorghum, we assessed 14 herbicide programs, of which 8 were PRE only and 6 were PRE followed by (fb) POST applications. Visible ratings of Palmer amaranth control were taken at 3 and 8 wk after planting (WAP) grain sorghum. PRE treatments containing very-long-chain fatty acid (VLCFA)–inhibiting herbicides provided 91% control of atrazine-resistant Palmer amaranth 3 WAP, and reduced weed density 8 WAP compared to atrazine-only PRE treatments. PRE fb POST treatments, especially those that included VLCFA-inhibiting herbicides, provided greater control (71% to 93%) of both atrazine-resistant and atrazine-susceptible Palmer amaranth, respectively, at 8 WAP compared to PRE treatments alone (59% to 79%). These results demonstrated the utility of VLCFA-inhibiting herbicides applied PRE and in a layered PRE fb POST approach in controlling atrazine-resistant Palmer amaranth, as well as the importance of an effective POST application following residual PRE herbicides for controlling both atrazine-resistant and atrazine-susceptible Palmer amaranth in double-crop grain sorghum.

Susceptibility of Palmer amaranth (Amaranthus palmeri) to herbicides in accessions collected from the North Carolina Coastal Plain

Weed Science ◽  
2020 ◽  
Vol 68 (6) ◽  
pp. 582-593
Author(s):  
Denis J. Mahoney ◽  
David L. Jordan ◽  
Nilda Roma-Burgos ◽  
Katherine M. Jennings ◽  
Ramon G. Leon ◽  
...  
Keyword(s):  
North Carolina ◽  
Dose Response ◽  
Coastal Plain ◽  
Weed Management ◽  
Acetolactate Synthase ◽  
Fold Increase ◽  
Palmer Amaranth ◽  
Amaranthus Palmeri ◽  
Sites Of Action ◽  
Two Populations

AbstractPalmer amaranth (Amaranthus palmeri S. Watson) populations resistant to acetolactate synthase (ALS)-inhibiting herbicides and glyphosate are fairly common throughout the state of North Carolina (NC). This has led farm managers to rely more heavily on herbicides with other sites of action (SOA) for A. palmeri control, especially protoporphyrinogen oxidase and glutamine synthetase inhibitors. In the fall of 2016, seeds from A. palmeri populations were collected from the NC Coastal Plain, the state’s most prominent agricultural region. In separate experiments, plants with 2 to 4 leaves from the 110 populations were treated with field use rates of glyphosate, glufosinate-ammonium, fomesafen, mesotrione, or thifensulfuron-methyl. Percent visible control and survival were evaluated 3 wk after treatment. Survival frequencies were highest following glyphosate (99%) or thifensulfuron-methyl (96%) treatment. Known mutations conferring resistance to ALS inhibitors were found in populations surviving thifensulfuron-methyl application (Ala-122-Ser, Pro-197-Ser, Trp-574-Leu, and/or Ser-653-Asn), in addition to a new mutation (Ala-282-Asp) that requires further investigation. Forty-two populations had survivors after mesotrione application, with one population having 17% survival. Four populations survived fomesafen treatment, while none survived glufosinate. Dose–response studies showed an increase in fomesafen needed to kill 50% of two populations (LD50); however, these rates were far below the field use rate (less than 5 g ha−1). In two populations following mesotrione dose–response studies, a 2.4- to 3.3-fold increase was noted, with LD90 values approaching the field use rate (72.8 and 89.8 g ha−1). Screening of the progeny of individuals surviving mesotrione confirmed the presence of resistance alleles, as there were a higher number of survivors at the 1X rate compared with the parent population, confirming resistance to mesotrione. These data suggest A. palmeri resistant to chemistries other than glyphosate and thifensulfuron-methyl are present in NC, which highlights the need for weed management approaches to mitigate the evolution and spread of herbicide-resistant populations.

scholarly journals Point Mutations as Main Resistance Mechanism Together With P450-Based Metabolism Confer Broad Resistance to Different ALS-Inhibiting Herbicides in Glebionis coronaria From Tunisia

2021 ◽  
Vol 12 ◽  
Author(s):  
Zeineb Hada ◽  
Yosra Menchari ◽  
Antonia M. Rojano-Delgado ◽  
Joel Torra ◽  
Julio Menéndez ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Dose Response ◽  
Resistance Mechanism ◽  
Point Mutations ◽  
Acetolactate Synthase ◽  
Target Site ◽  
Cross Resistance ◽  
P450 Monooxygenase ◽  
Target Site Resistance ◽  
Sites Of Action

Resistance to acetolactate synthase (ALS) inhibiting herbicides has recently been reported in Glebionis coronaria from wheat fields in northern Tunisia, where the weed is widespread. However, potential resistance mechanisms conferring resistance in these populations are unknown. The aim of this research was to study target-site resistance (TSR) and non-target-site resistance (NTSR) mechanisms present in two putative resistant (R) populations. Dose–response experiments, ALS enzyme activity assays, ALS gene sequencing, absorption and translocation experiments with radiolabeled herbicides, and metabolism experiments were carried out for this purpose. Whole plant trials confirmed high resistance levels to tribenuron and cross-resistance to florasulam and imazamox. ALS enzyme activity further confirmed cross-resistance to these three herbicides and also to bispyribac, but not to flucarbazone. Sequence analysis revealed the presence of amino acid substitutions in positions 197, 376, and 574 of the target enzyme. Among the NTSR mechanisms investigated, absorption or translocation did not contribute to resistance, while evidences of the presence of enhanced metabolism were provided. A pretreatment with the cytochrome P450 monooxygenase (P450) inhibitor malathion partially synergized with imazamox in post-emergence but not with tribenuron in dose–response experiments. Additionally, an imazamox hydroxyl metabolite was detected in both R populations in metabolism experiments, which disappeared with the pretreatment with malathion. This study confirms the evolution of cross-resistance to ALS inhibiting herbicides in G. coronaria from Tunisia through TSR and NTSR mechanisms. The presence of enhanced metabolism involving P450 is threatening the chemical management of this weed in Tunisian wheat fields, since it might confer cross-resistance to other sites of action.

scholarly journals Evaluation of Preemergence Herbicide Programs for Control of Protoporphyrinogen Oxidase-Resistant Amaranthus palmeri in Soybean

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Michael M. Houston ◽  
L. Tom Barber ◽  
Jason K. Norsworthy ◽  
Trent L. Roberts
Keyword(s):  
Acetolactate Synthase ◽  
Field Trials ◽  
Palmer Amaranth ◽  
Amaranthus Palmeri ◽  
Long Chain Fatty Acid ◽  
Protoporphyrinogen Oxidase ◽  
Density Reduction ◽  
Glycine Max L ◽  
Sites Of Action ◽  
Herbicide Programs

Protoporphyrinogen oxidase- (PPO-) resistant Amaranthus palmeri (S.) Wats. (Palmer amaranth) was confirmed in Arkansas in 2015. Field trials were conducted in Crawfordsville, Gregory, and Marion, Arkansas in 2016, and Crawfordsville and Marion in 2017, assessing PPO-resistant Palmer amaranth control options in Glycine max (L.) Merr. (soybean). Twelve trials consisted of 26 preemergence (PRE) treatments, evaluated for Palmer amaranth control and density reduction at 28 days after treatment (DAT). Treatments that consisted of PPO- or acetolactate synthase- (ALS-) inhibiting herbicides such as flumioxazin (72 g ai ha−1) or sulfentrazone + cloransulam (195 g ha−1 + 25 g ha−1) controlled Palmer amaranth <60%. At 28 DAT, treatments including mixtures of a very-long-chain fatty acid (VLCFA) plus the photosystem II- (PSII-) inhibiting herbicide metribuzin provided increased control over single herbicide sites of action (SOA) or herbicides mixtures to which Palmer amaranth was resistant. Pyroxasulfone + metribuzin (149 g ha−1 + 314 g ha−1) controlled Palmer amaranth 91% control across twelve trials at 28 DAT. S-metolachlor alone did not provide consistent, acceptable control of PPO-resistant Palmer amaranth (55–77%); subsequent research has determined that these populations are resistant to S-metolachlor. A minimum of two effective herbicides should be included in soybean PRE programs for control of PPO-resistant Palmer amaranth.

Control and Cross-Resistance of an Acetolactate Synthase Inhibitor-Resistant Palmer Amaranth (Amaranthus palmeri) Biotype

1997 ◽  
Vol 11 (1) ◽  
pp. 132-137 ◽  
Author(s):  
Jason W. Gaeddert ◽  
Dallas E. Peterson ◽  
Michael J. Horak
Keyword(s):  
Rate Control ◽  
Cultural Practices ◽  
Acetolactate Synthase ◽  
Mechanisms Of Action ◽  
Palmer Amaranth ◽  
Cross Resistance ◽  
Amaranthus Palmeri ◽  
Partial Control ◽  
Synthase Inhibitor ◽  
Control Tank

Over two years, acetolactate synthase (ALS)-inhibiting herbicides and herbicides with different mechanisms of action were tested individually and in combination for control of ALS-resistant Palmer amaranth in soybean. As expected, ALS-inhibiting herbicides did not control the resistant Palmer amaranth. Lactofen at 210 g/ha and acifluorfen at 560 g/ha gave the best postemergence control. Tank mixes of lactofen with either imazethapyr or chlorimuron plus thifensulfuron did not significantly increase control over lactofen alone. Sequential treatment with a soil-applied herbicide, either SAN 582 or pendimethalin, followed by lactofen postemergence, controlled weeds best (greater than 85%). The extent of cross-resistance of Palmer amaranth to ALS-inhibiting herbicides was determined in the greenhouse. Sixteen POST ALS-inhibiting herbicides were sprayed at ½, 1, 2, 4, and 8X field use rates on resistant and susceptible biotypes. All ALS-inhibiting herbicides at all rates controlled the susceptible biotype. The resistant biotype was cross-resistant to all ALS-inhibiting herbicides. Metsulfuron and imazapyr at 8X rates were the only treatments that provided 80% or greater control of the ALS-resistant Palmer amaranth. Chlorsulfuron and tribenuron were the only other herbicides that gave partial control at the highest rate. Control with these four herbicides decreased as the rate was decreased. Experimental results suggest that cultural practices and herbicides with different mechanisms of action will be required to manage this ALS-resistant Palmer amaranth biotype.

scholarly journals Investigating the Efficacy of Selected Very-Long-Chain Fatty Acid-Inhibiting Herbicides on Iowa Waterhemp (Amaranthus tuberculatus) Populations with Evolved Multiple Herbicide Resistances

Agronomy ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 595
Author(s):  
Eric A. L. Jones ◽  
Micheal D. K. Owen
Keyword(s):  
Fatty Acid ◽  
Dose Response ◽  
Chain Fatty Acid ◽  
Long Chain Fatty Acid ◽  
Midwest United States ◽  
Herbicide Resistant ◽  
Amaranthus Tuberculatus ◽  
The 1960S ◽  
Sites Of Action ◽  
Long Chain

Very long chain fatty acid (VLCFA)-inhibiting herbicides (Herbicide group (HG) 15) have been applied to corn and soybean fields in Iowa since the 1960s. The VLCFA-inhibiting herbicides are now applied more frequently to control multiple herbicide-resistant (MHR) waterhemp (Amaranthus tuberculatus Moq. J.D. Sauer) populations that are ubiquitous across the Midwest United States as resistance to the VLCFA-inhibiting herbicides is not widespread. Waterhemp has evolved multiple resistances to herbicides from seven sites of action (HG 2, 4, 5, 9, 14, 15, and 27), and six-way herbicide-resistant populations have been confirmed. Thus, the objective of this study was to determine if selected Iowa waterhemp populations are less sensitive to VLCFA-inhibiting herbicides when additional herbicide resistance traits have evolved within the selected population. Dose–response assays were conducted in a germination chamber to determine the efficacy of three selected VLCFA-inhibiting herbicides (acetochlor, S-metolachlor, and flufenacet) on selected Iowa MHR waterhemp populations. An herbicide-susceptible, three-way, four-way, and five-way herbicide-resistant waterhemp population responded to the herbicide treatments differently; however, several of the four-way and five-way herbicide-resistant populations exhibited resistance ratios greater than 1 when treated with acetochlor and S-metolachlor. Selected four-way herbicide-resistant waterhemp populations from Iowa were subjected to a dose–response assay in the field using the same VLCFA-inhibiting herbicides, and all herbicides achieved control greater than 80% at the maximum labeled rate. The results of the experiments provide evidence that some MHR waterhemp populations may exhibit decreased susceptibility the VLCFA-inhibiting herbicides, but generally, these herbicides remain efficacious on Iowa MHR waterhemp populations.

Resistance to very-long-chain fatty-acid (VLCFA)-inhibiting herbicides in multiple field-selected rigid ryegrass (Lolium rigidum) populations

Weed Science ◽  
2019 ◽  
Vol 67 (3) ◽  
pp. 267-272 ◽  
Author(s):  
David J. Brunton ◽  
Peter Boutsalis ◽  
Gurjeet Gill ◽  
Christopher Preston
Keyword(s):  
Fatty Acid ◽  
Dose Response ◽  
Chain Fatty Acid ◽  
Lolium Rigidum ◽  
Long Chain Fatty Acid ◽  
First Case ◽  
Rigid Ryegrass ◽  
Multiple Field ◽  
Dose Response Study ◽  
Long Chain

AbstractFive populations of rigid ryegrass (Lolium rigidumGaudin) from fields across cropping regions in southern Australia were suspected of having resistance to thiocarbamates, chloroacetamides, and sulfonylisoxazoline herbicides. Resistant (R) populations 375-14, 198-15, 16.2, EP162, RAC1, and A18 and two susceptible (S) populations (SLR4 and VLR1) were included in a dose–response study. All suspected R populations expressed resistance to one or all herbicides (thiocarbamates, chloroacetamides, and pyroxasulfone). Population 198-15 exhibited the highest LD50to triallate (44.7-fold), prosulfocarb (45.7-fold),S-metolachlor (31.5-fold), and metazachlor (27.2-fold) compared with the S populations. Populations 198-15 and 375-14 were also resistant to pyroxasulfone (13.5- and 14.9-fold) compared with the S populations, as was population EP162. This study documents the first case of field-evolved resistance to thiocarbamate, chloroacetamide, and sulfonylisoxazoline herbicides inL. rigidum.

Palmer amaranth (Amaranthus palmeri) and common waterhemp (Amaranthus rudis) resistance to selected ALS-inhibiting herbicides

Weed Science ◽  
1997 ◽  
Vol 45 (2) ◽  
pp. 192-197 ◽  
Author(s):  
Christy L. Sprague ◽  
Edward W. Stoller ◽  
Loyd M. Wax ◽  
Michael J. Horak
Keyword(s):  
Acetolactate Synthase ◽  
Palmer Amaranth ◽  
Cross Resistance ◽  
Amaranthus Palmeri ◽  
Sulfonylurea Herbicides ◽  
Common Waterhemp ◽  
Whole Plant ◽  
Amaranthus Rudis

Imazethapyr-resistant biotypes of Palmer amaranth and common waterhemp were studied to determine the magnitude of resistance and cross-resistance to three acetolactate synthase (ALS)-inhibiting herbicides. Resistant biotypes of Palmer amaranth and common waterhemp demonstrated > 2,800- and > 130-fold resistance to phytotoxicity of imazethapyr compared to susceptible biotypes, respectively. Concentrations of imazethapyr required for 50% in vivo inhibition of ALS activity were at least > 13,100 and > 1,900 times greater for resistant biotypes of Palmer amaranth and common waterhemp, respectively, compared to susceptible plants. Resistant biotypes of both species demonstrated cross-resistance to the sulfonylurea herbicides thifensulfuron and chlorimuron at the whole plant and enzyme levels, indicating that a less sensitive ALS enzyme confers this resistance to these plants.

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