International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
GROUP C3/6 RESISTANT SMOOTH PIGWEED
(Amaranthus hybridus (syn: quitensis))


PSII inhibitors (Nitriles) (C3/6)

Canada, Ontario
INTRODUCTION SMOOTH PIGWEED
Smooth Pigweed (Amaranthus hybridus (syn: quitensis)) is a dicot weed in the Amaranthaceae family.  In Ontario this weed first evolved resistance to Group C3/6 herbicides in 2004 and infests Corn (maize).   Group C3/6 herbicides are known as PSII inhibitors (Nitriles) (Inhibition of photosynthesis at photosystem II).  Research has shown that these particular biotypes are resistant to bentazon, and bromoxynil and they may be cross-resistant to other Group C3/6 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 Feb 18, 2010 )

Common NameSmooth Pigweed
SpeciesAmaranthus hybridus (syn: quitensis)
GroupPSII inhibitors (Nitriles) (C3/6)
Herbicidesbentazon, and bromoxynil
LocationCanada, Ontario
Year2004
Situation(s)Corn (maize)
Contributors - (Alphabetically)Francois Tardif 
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Smooth Pigweed biotype with this Smooth 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 Group C3/6 resistant Smooth 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 C3/6 resistant Smooth Pigweed from Ontario please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

FRANCOIS TARDIF
Associate Professor
University Of Guelph
Department Of Plant Agriculture
2055 Radatz Ave
Guelph, N1G 2W1, Ontario
Canada
Email Francois Tardif
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Ontario have been instrumental in providing you this information. Particular thanks is given to Francois Tardif for providing detailed information.
Herbicide Resistant Smooth Pigweed Globally
(Amaranthus hybridus (syn: quitensis))
Herbicide Resistant Smooth Pigweed Globally
(Amaranthus hybridus (syn: quitensis))
Drag a column header and drop it here to group by that column
Herbicide Resistant Smooth Pigweed Globally
(Amaranthus hybridus (syn: quitensis))
#CountryFirstYearSituationActive IngredientsSite of Action
1 ArgentinaArgentina 1996 Soybean chlorimuron-ethyl, and imazethapyr 48 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5099
2 ArgentinaArgentina 2013 Soybean glyphosate 48 EPSP synthase inhibitors (G/9)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed6757
3 ArgentinaArgentina 2014 Corn (maize), and Soybean glyphosate, and imazethapyr 48 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed9948
4 BoliviaBolivia 2002 Soybean chlorimuron-ethyl, imazamox, imazethapyr, and oxasulfuron 4 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5242
5 BoliviaBolivia 2005 Soybean fomesafen, lactofen, and sulfentrazone 4 PPO inhibitors (E/14)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5411
6 Canada (Ontario) CanadaOntario2004 Corn (maize) bentazon, and bromoxynil 7 PSII inhibitors (Nitriles) (C3/6)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5472
7 FranceFrance 1980 Corn (maize) atrazine 17 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed453
8 IsraelIsrael 1986 Cropland atrazine 23 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed101
9 ItalyItaly 1978 Corn (maize) atrazine 24 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed114
10 South AfricaSouth Africa 1993 Corn (maize) atrazine 37 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed193
11 SpainSpain 1985 Corn (maize) atrazine 38 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed175
12 SwitzerlandSwitzerland 1982 Vegetables simazine 41 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed198
13 United States (Maryland) United StatesMaryland1972 Corn (maize), and Cropland atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed429
14 United States (Virginia) United StatesVirginia1976 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed273
15 United States (Delaware) United StatesDelaware1977 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed492
16 United States (North Carolina) United StatesNorth Carolina1980 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed262
17 United States (Pennsylvania) United StatesPennsylvania1980 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed264
18 United States (New Jersey) United StatesNew Jersey1980 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed494
19 United States (New York) United StatesNew York1980 Corn (maize) atrazine, metribuzin, and simazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5225
20 United States (Wisconsin) United StatesWisconsin1985 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed418
21 United States (Kentucky) United StatesKentucky1987 Corn (maize) atrazine, and simazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed489
22 United States (Kentucky) United StatesKentucky1992 Soybean chlorimuron-ethyl, flumetsulam, imazaquin, imazethapyr, nicosulfuron, primisulfuron-methyl, and thifensulfuron-methyl 45 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed490
23 United States (Illinois) United StatesIllinois1993 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed236
24 United States (Virginia) United StatesVirginia1994 Corn (maize), and Soybean imazaquin, and imazethapyr 45 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed278
25 United States (Illinois) United StatesIllinois1998 Soybean imazethapyr, and primisulfuron-methyl 45 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed7859
26 United States (Delaware) United StatesDelaware2000 Vegetables imazethapyr 45 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5160
27 United States (Illinois) United StatesIllinois2000 Corn (maize) atrazine, imazethapyr, and primisulfuron-methyl 45 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
Photosystem II inhibitors (C1/5)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed7860
28 United States (Ohio) United StatesOhio2001 Soybean flumetsulam, and thifensulfuron-methyl 45 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5233
29 United States (Michigan) United StatesMichigan2002 Soybean chlorimuron-ethyl, imazamox, and thifensulfuron-methyl 45 ALS inhibitors (B/2)
12Amaranthus hybridus (syn: quitensis)Smooth Pigweed5170
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