International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
GROUP B/2 RESISTANT POWELL AMARANTH
(Amaranthus powellii)


ALS inhibitors (B/2)

Canada, Ontario
INTRODUCTION POWELL AMARANTH
Powell Amaranth (Amaranthus powellii) is a dicot weed in the Amaranthaceae family.  In Ontario this weed first evolved resistance to Group B/2 herbicides in 1998 and infests Corn (maize), Cropland, and Soybean.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)).  Research has shown that these particular biotypes are resistant to imazethapyr, and thifensulfuron-methyl and they may be cross-resistant to other Group B/2 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 Apr 28, 2011 )

Common NamePowell Amaranth
SpeciesAmaranthus powellii
GroupALS inhibitors (B/2)
Herbicidesimazethapyr, and thifensulfuron-methyl
LocationCanada, Ontario
Year1998
Situation(s)Corn (maize), Cropland, and Soybean
Contributors - (Alphabetically)Francois Tardif 
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NOTES ABOUT THIS BIOTYPE

GENERAL

Hugh Beckie
Ferguson, G. M., R. S. Diebold, F. J. Tardif, and A. S. Hamill. 2000. Populations of green pigweed (Amaranthus powellii) and redroot pigweed (Amaranthus retroflexus) in Ontario show different patterns of resistance to ALS-inhibiting herbicides and to triazines. Weed Sci. Soc. Am. Abstr. 40:47-48. Also: Ferguson, G. M., A. S. Hamill, and F. Tardif. 2000. Characterization of imazethapyr and flumetsulam resistance and cross resistance to thifensulfuron-methyl in populations of Amaranthus powellii S. Wats. and A. retroflexus L. in Ontario. Abstr. Third International Weed Science Congress, Foz do Iguassu, Brazil. Corvallis, OR: International Weed Science Society. p. 152.

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OTHER CONTACTS

Francois Tardif
Amaranthus powellii S. wats to imazethapyr in 1998 in Ontario (Gabriel Ferguson and Al Hamill, AAFC).

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Powell Amaranth biotype with this Powell Amaranth 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 B/2 resistant Powell Amaranth indicate that the inheritance is determined by a one gene, semi dominant, nuclear trait.  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

Studies on the mechanism of resistance of Group B/2 resistant Powell Amaranth from Ontario indicate that resistance is due to an altered target site.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
 
Relative Fitness

Researchers have indicated that Group B/2 resistant Powell Amaranth is ecologically less fit than normal susceptible Powell Amaranth.  There may be a note below or an article discussing the fitness of this biotype in the Fact Sheets and Other Literature
 
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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 Powell Amaranth Globally
(Amaranthus powellii)
Herbicide Resistant Powell Amaranth Globally
(Amaranthus powellii)
Drag a column header and drop it here to group by that column
Herbicide Resistant Powell Amaranth Globally
(Amaranthus powellii)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Canada (Ontario) CanadaOntario1977 Corn (maize) atrazine, and metribuzin 7 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth1158
2 Canada (Ontario) CanadaOntario1998 Corn (maize), Cropland, and Soybean imazethapyr, and thifensulfuron-methyl 7 ALS inhibitors (B/2)
15Amaranthus powelliiPowell Amaranth1159
3 Canada (Ontario) CanadaOntario1998 Corn (maize), Soybean, and Wheat atrazine, imazethapyr, and metribuzin 7 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth5049
4 Canada (Ontario) CanadaOntario1999 Carrots atrazine, linuron, monolinuron, and prometryn 7 Multiple Resistance: 2 Sites of Action
Photosystem II inhibitors (C1/5)
PSII inhibitor (Ureas and amides) (C2/7)
15Amaranthus powelliiPowell Amaranth5048
5 Canada (Manitoba) CanadaManitoba2008 Beans, and Wheat thifensulfuron-methyl, and tribenuron-methyl 7 ALS inhibitors (B/2)
15Amaranthus powelliiPowell Amaranth5631
6 Czech RepublicCzech Republic 1989 Orchards atrazine, cyanazine, prometryn, simazine, and terbutryn 12 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth78
7 FranceFrance 1982 Corn (maize) atrazine 17 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth452
8 SwitzerlandSwitzerland 1986 Corn (maize) atrazine 41 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth197
9 United States (Washington) United StatesWashington1992 Mint terbacil 45 Photosystem II inhibitors (C1/5)
15Amaranthus powelliiPowell Amaranth331
10 United States (Ohio) United StatesOhio1996 Soybean imazaquin 45 ALS inhibitors (B/2)
15Amaranthus powelliiPowell Amaranth1100
11 United States (Michigan) United StatesMichigan2001 Asparagus, and Nurseries atrazine, and diuron 45 Multiple Resistance: 2 Sites of Action
Photosystem II inhibitors (C1/5)
PSII inhibitor (Ureas and amides) (C2/7)
15Amaranthus powelliiPowell Amaranth5176
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