INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 2 (LEGACY B) RESISTANT REDROOT PIGWEED
(Amaranthus retroflexus)


Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Ukraine, Cherkassy region
INTRODUCTION REDROOT PIGWEED
Redroot Pigweed (Amaranthus retroflexus) is a dicot weed in the Amaranthaceae family.  In Ukraine this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2020 and infests Corn (maize), and Sunflower.   Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ).  Research has shown that these particular biotypes are resistant to florasulam, flumetsulam, foramsulfuron, imazamox, imazethapyr, iodosulfuron-methyl-Na, thiencarbazone-methyl, thifensulfuron-methyl, and tribenuron-methyl and they may be cross-resistant to other Group 2 (Legacy B) herbicides.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

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QUIK STATS (last updated Aug 30, 2021 )

Common NameRedroot Pigweed
SpeciesAmaranthus retroflexus
GroupInhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicidesflorasulam, flumetsulam, foramsulfuron, imazamox, imazethapyr, iodosulfuron-methyl-Na, thiencarbazone-methyl, thifensulfuron-methyl, and tribenuron-methyl
LocationUkraine, Cherkassy region
Year2020
Situation(s)Corn (maize), and Sunflower
Contributors - (Alphabetically)Liudmyla M Mykhalska, and Victor Schwartau 
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NOTES ABOUT THIS BIOTYPE

GENERAL

Victor Schwartau

Mykhalska, L. M., & Schwartau, V. V. (2022). Identification of acetolactate synthase resistant Amaranthus retroflexus in Ukraine. Regulatory Mechanisms in Biosystems, 13(3), 231–240. doi:10.15421/022230 Click title for full paper.

Abstract

 The problem of weed resistance to herbicides has become very important in the last decade and threatens to dramatically reduce the productivity and profitability of modern crop production. Herbicides – ALS inhibitors dominate among current herbicides and are used annually on large areas of sunflower, wheat, corn, soybean, and rapeseed. Also, in recent years, Clearfield seeds of sunflower, corn, canola, soybean and wheat have been sown in large areas. In recent years, there has been a sharp decrease in Amaranthus retroflexus L. control levels by imidazolinone class herbicides. Thus, the effects of herbicides with different modes of action on the development of A. retroflexus on sunflower after imidazolinone application were investigated in field research. In the conditions of the Cherkasy region of Ukraine, the biotype A. retroflexus was identified, which is resistant to the post-emergence application of herbicides - acetolactate synthase (ALS) inhibitors of the imidazolinone class – imazapyr and imazamox. Weed plants treated with imidazolinone derivatives in the maximum doses registered in Ukraine did not differ from untreated control plants. Also, in the conditions of field experiments, cross resistance of the weed biotype to herbicides – ALS inhibitors of the sulfonylurea class – foramsulfuron and iodosulfuron-methyl-sodium, thifensulfuron-methyl, tribenuron-methyl, nicosulfuron was established; and also, to the triazolinone derivative – thiencarbazone-methyl; to triazolpyrimidine derivatives – florasulam and flumetsulam. Multiple resistance of the A. retroflexus biotype to herbicides of the classes of glycine derivatives – glyphosate, phenoxycarboxylates – 2,4-D, benzoic acid – dicamba has not been established; compositions of dicamba with triketone – topramesone; diphenyl ethers – aclonifen; pyridine carboxylates – clopyralid, picloram and aminopyralid. It was shown for the first time that herbicide compositions with selected nutrients (ammonium pool) can increase the level of effectiveness of controlling resistant weed biotypes. Thus, the addition of ammonium sulfate increases the effectiveness of controlling ALS-resistant A. retroflexus with herbicides – a derivative of benzoic acid (dianate) and a derivative of benzoic acid with a 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor (stellar – dicamba + topramesone). Thus, the A. retroflexus biotype resistant to ALS-herbicides of the imidazolinone class was identified for the first time in Ukraine, which is cross-resistant to other ALS-inhibitors of the sulfonylureas, triazolinones, and triazolpyrimidine classes. Multiple resistance of A. retroflexus to herbicides of the classes of glycine derivatives – glyphosate; phenoxycarboxylates – 2,4-D; benzoic acid – dicamba, triketones – topramesone; diphenyl ethers – aclonifen; pyridine carboxylates – clopyralid, picloram and aminopyralid has not been established. The identification of a highly harmful weed species resistant to widely used herbicides – ALS inhibitors in the central part of the "grain belt" of Ukraine requires a significant revision of the principles of crop rotation formation and ways of controlling weeds in the country in order to maintain high levels of profitability and productivity of agrophytocenoses. 

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ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Redroot Pigweed biotype with this Redroot Pigweed biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.
 
Genetics

Genetic studies on HRAC Group 2 resistant Redroot Pigweed have not been reported to the site.  There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature
 
Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database.  If you know anything about the mechanism of resistance for this biotype then please update the database.
 
Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes.  If you have any information pertaining to the fitness of Group 2 (Legacy B) resistant Redroot Pigweed from Ukraine please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

LIUDMYLA M MYKHALSKA
Senior Research Scientist
Institute of Plant Physiology and Genetics, National Academy of Science of Ukraine
Department of Plant Nutrition Physiology
31/17, Vasylkivska St.
Kyiv-22, 03022, Kyiv Region
Ukraine
Email Liudmyla M Mykhalska
VICTOR SCHWARTAU
Department Head
Institute of Plant Physiology and Genetics, National Academy of Science of Ukraine
Department of Plant Nutrition Physiology
31/17, Vasylkivska St.
Kyiv-22, 03022, Kyiv Region
Ukraine
Email Victor Schwartau

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Ukraine have been instrumental in providing you this information. Particular thanks is given to Liudmyla M Mykhalska, and Victor Schwartau for providing detailed information.
Herbicide Resistant Redroot Pigweed Globally
(Amaranthus retroflexus)
Herbicide Resistant Redroot Pigweed Globally
(Amaranthus retroflexus)
Drag a column header and drop it here to group by that column
Herbicide Resistant Redroot Pigweed Globally
(Amaranthus retroflexus)
#CountryFirstYearSituationActive IngredientsSite of Action
1 BrazilBrazil 2011 Cotton atrazine, prometryne, and trifloxysulfuron-Na 5 Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5734
2 BrazilBrazil 2012 Cotton pyrithiobac-sodium, and trifloxysulfuron-Na 5 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed5733
3 BrazilBrazil 2014 Cotton, and Soybean fomesafen 5 Inhibition of Protoporphyrinogen Oxidase ( HRAC Group 14 (Legacy E)
16Amaranthus retroflexusRedroot Pigweed13033
4 BulgariaBulgaria 1984 Corn (maize), Cropland, Grapes, and Orchards atrazine, metribuzin, and simazine 6 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed44
5 BulgariaBulgaria 1984 Cropland linuron 6 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed45
6 Canada (Ontario) CanadaOntario1980 Corn (maize), and Cropland atrazine 7 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed61
7 Canada (Quebec) CanadaQuebec1980 Corn (maize) atrazine, and metribuzin 7 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed17126
8 Canada (Ontario) CanadaOntario1998 Corn (maize), Cropland, and Soybean imazethapyr, and thifensulfuron-methyl 7 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed1161
9 Canada (Ontario) CanadaOntario2001 Carrots, and Vegetables linuron 7 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5125
10 Canada (Quebec) CanadaQuebec2001 Carrots linuron 7 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5126
11 Canada (Manitoba) CanadaManitoba2002 Wheat florasulam 7 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed5222
12 Canada (Ontario) CanadaOntario2005 Corn (maize) bentazon, and bromoxynil 7 PSII inhibitors - Histidine 215 Binders ( HRAC Group 6 (Legacy C3)
16Amaranthus retroflexusRedroot Pigweed5473
13 Canada (Quebec) CanadaQuebec2009 Soybean imazethapyr 7 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed17125
14 Canada (Saskatchewan) CanadaSaskatchewan2010 Wheat thifensulfuron-methyl, and tribenuron-methyl 7 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed5628
15 ChinaChina 1990 Cropland atrazine 9 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed1141
16 ChinaChina 2017 Soybean acifluorfen, fluoroglycofen-ethyl, fomesafen, imazethapyr, and lactofen 9 Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
Inhibition of Protoporphyrinogen Oxidase ( HRAC Group 14 (Legacy E)
16Amaranthus retroflexusRedroot Pigweed16078
17 Czech RepublicCzech Republic 1985 Corn (maize), Railways, Roadsides, and Sugar beets atrazine, cyanazine, metamitron, prometryne, terbuthylazine, and terbutryne 12 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed77
18 FranceFrance 1980 Corn (maize) atrazine 17 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed455
19 GermanyGermany 1980 Corn (maize), Railways, and Roadsides atrazine, and fenuron 18 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed370
20 GermanyGermany 2012 Corn (maize) nicosulfuron 18 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed6742
21 GreeceGreece 2000 Potatoes metribuzin 19 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5058
22 IsraelIsrael 1991 Forests chlorsulfuron 23 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed106
23 ItalyItaly 1999 Corn (maize), Soybean, and Sugar beets chloridazon/pyrazon, metamitron, and terbuthylazine 24 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5115
24 ItalyItaly 2003 Soybean imazamox, imazethapyr, nicosulfuron, oxasulfuron, and thifensulfuron-methyl 24 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed5248
25 PolandPoland 1991 Orchards, and Sugar beets atrazine, and metamitron 33 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed164
26 SerbiaSerbia 2002 Soybean imazethapyr 245 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed5216
27 SpainSpain 1986 Corn (maize) atrazine 38 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed187
28 SwitzerlandSwitzerland 1982 Grapes, Orchards, and Vegetables simazine 41 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed199
29 UkraineUkraine 2020 Corn (maize), and Sunflower florasulam, flumetsulam, foramsulfuron, imazamox, imazethapyr, iodosulfuron-methyl-Na, thiencarbazone-methyl, thifensulfuron-methyl, and tribenuron-methyl 230 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed20231
30 United States (Indiana) United StatesIndiana1980 Cropland atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed408
31 United States (Colorado) United StatesColorado1982 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed430
32 United States (Connecticut) United StatesConnecticut1984 Corn (maize) atrazine, and cyanazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed1071
33 United States (New Hampshire) United StatesNew Hampshire1984 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed1078
34 United States (Maine) United StatesMaine1985 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed1092
35 United States (Minnesota) United StatesMinnesota1991 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed245
36 United States (Vermont) United StatesVermont1991 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed1101
37 United States (Virginia) United StatesVirginia1993 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed373
38 United States (Oregon) United StatesOregon1994 Mint terbacil 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed321
39 United States (Arkansas) United StatesArkansas1995 Cropland, and Soybean imazaquin 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed402
40 United States (Kansas) United StatesKansas1995 Corn (maize), and Sorghum atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed1039
41 United States (Maryland) United StatesMaryland1998 Unspecified imazaquin, and imazethapyr 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed1085
42 United States (Pennsylvania) United StatesPennsylvania1998 Corn (maize), Soybean, and Tomatoes atrazine, chlorimuron-ethyl, cloransulam-methyl, imazamox, imazaquin, imazethapyr, primisulfuron-methyl, and thifensulfuron-methyl 45 Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5021
43 United States (North Dakota) United StatesNorth Dakota1999 Soybean imazethapyr 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed5046
44 United States (West Virginia) United StatesWest Virginia2000 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed7773
45 United States (Michigan) United StatesMichigan2001 Asparagus atrazine, and diuron 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5177
46 United States (Idaho) United StatesIdaho2005 Potatoes metribuzin 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5293
47 United States (Washington) United StatesWashington2010 Mint, and Potatoes metribuzin, and terbacil 45 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
16Amaranthus retroflexusRedroot Pigweed5667
48 United States (Mississippi) United StatesMississippi2010 Railways imazethapyr, pyrithiobac-sodium, and trifloxysulfuron-Na 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
16Amaranthus retroflexusRedroot Pigweed16079
49 United States (North Carolina) United StatesNorth Carolina2020 Soybean fomesafen, imazamethabenz-methyl, lactofen, and thifensulfuron-methyl 45 Multiple Resistance: 2 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
Inhibition of Protoporphyrinogen Oxidase ( HRAC Group 14 (Legacy E)
16Amaranthus retroflexusRedroot Pigweed22235
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