INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE
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Herbicide Resistant Redroot Pigweed Globally
(Amaranthus retroflexus)
Herbicide Resistant Redroot Pigweed Globally
(Amaranthus retroflexus)
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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 Canada (Prince Edward Island) CanadaPrince Edward Island2023 Potatoes linuron, and metribuzin 7 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed28274
16 ChinaChina 1990 Cropland atrazine 9 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed1141
17 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
18 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
19 FranceFrance 1980 Corn (maize) atrazine 17 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed455
20 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
21 GermanyGermany 2012 Corn (maize) nicosulfuron 18 Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
 		16Amaranthus retroflexusRedroot Pigweed6742
22 GreeceGreece 2000 Potatoes metribuzin 19 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed5058
23 IsraelIsrael 1991 Forests chlorsulfuron 23 Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
 		16Amaranthus retroflexusRedroot Pigweed106
24 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
25 ItalyItaly 2003 Soybean imazamox, imazethapyr, nicosulfuron, oxasulfuron, and thifensulfuron-methyl 24 Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
 		16Amaranthus retroflexusRedroot Pigweed5248
26 PolandPoland 1991 Orchards, and Sugar beets atrazine, and metamitron 33 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed164
27 SerbiaSerbia 2002 Soybean imazethapyr 245 Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
 		16Amaranthus retroflexusRedroot Pigweed5216
28 SpainSpain 1986 Corn (maize) atrazine 38 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed187
29 SwitzerlandSwitzerland 1982 Grapes, Orchards, and Vegetables simazine 41 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed199
30 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
31 United States (Indiana) United StatesIndiana1980 Cropland atrazine 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed408
32 United States (Colorado) United StatesColorado1982 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed430
33 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
34 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
35 United States (Maine) United StatesMaine1985 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed1092
36 United States (Minnesota) United StatesMinnesota1991 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed245
37 United States (Vermont) United StatesVermont1991 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed1101
38 United States (Virginia) United StatesVirginia1993 Corn (maize) atrazine 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed373
39 United States (Oregon) United StatesOregon1994 Mint terbacil 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed321
40 United States (Arkansas) United StatesArkansas1995 Cropland, and Soybean imazaquin 45 Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
 		16Amaranthus retroflexusRedroot Pigweed402
41 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
42 United States (Maryland) United StatesMaryland1998 Unspecified imazaquin, and imazethapyr 45 Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
 		16Amaranthus retroflexusRedroot Pigweed1085
43 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
44 United States (North Dakota) United StatesNorth Dakota1999 Soybean imazethapyr 45 Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
 		16Amaranthus retroflexusRedroot Pigweed5046
45 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
46 United States (Michigan) United StatesMichigan2001 Asparagus atrazine, and diuron 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed5177
47 United States (Idaho) United StatesIdaho2005 Potatoes metribuzin 45 PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
 		16Amaranthus retroflexusRedroot Pigweed5293
48 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
49 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
50 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
51 United States (North Carolina) United StatesNorth Carolina2022 Soybean glyphosate 45 Inhibition of Enolpyruvyl Shikimate Phosphate Synthase HRAC Group 9 (Legacy G)
 		16Amaranthus retroflexusRedroot Pigweed24258
52 United States (North Carolina) United StatesNorth Carolina2022 Soybean fomesafen, imazamethabenz-methyl, lactofen, mesotrione, and thifensulfuron-methyl 45 Multiple Resistance: 3 Sites of Action
Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Inhibition of Protoporphyrinogen Oxidase HRAC Group 14 (Legacy E)
Inhibition of Hydroxyphenyl Pyruvate Dioxygenase HRAC Group 27 (Legacy F2)
 		16Amaranthus retroflexusRedroot Pigweed24259
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