International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
GROUP G/9 RESISTANT HORSEWEED
(Conyza canadensis)


EPSP synthase inhibitors (G/9)

United States, Iowa
INTRODUCTION HORSEWEED
Horseweed (Conyza canadensis) is a dicot weed in the Asteraceae family.  In Iowa this weed first evolved resistance to Group G/9 herbicides in 2011 and infests Corn (maize), and Soybean.   Group G/9 herbicides are known as EPSP synthase inhibitors (Inhibition of EPSP synthase).  Research has shown that these particular biotypes are resistant to glyphosate and they may be cross-resistant to other Group G/9 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.

If we do not have a picture for this weed, or you can provide a better picture (scan, digital camera etc) please please e-mail it to us.

QUIK STATS (last updated Sep 06, 2011 )

Common NameHorseweed
SpeciesConyza canadensis
GroupEPSP synthase inhibitors (G/9)
Herbicidesglyphosate
LocationUnited States, Iowa
Year2011
Situation(s)Corn (maize), and Soybean
Contributors - (Alphabetically)Micheal Owen 
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ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Horseweed biotype with this Horseweed 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 G/9 resistant Horseweed 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 G/9 resistant Horseweed from Iowa please update the database.
 
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CONTRIBUTING WEED SCIENTISTS

MICHEAL OWEN
Associate Chair And Professor
Iowa State University
Agronomy Department
3218 Agronomy Hall
Ames, 50011, Iowa
United States
Email Micheal Owen
Web   : Web Site Link

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Iowa have been instrumental in providing you this information. Particular thanks is given to Micheal Owen for providing detailed information.
Herbicide Resistant Horseweed Globally
(Conyza canadensis)
Herbicide Resistant Horseweed Globally
(Conyza canadensis)
Drag a column header and drop it here to group by that column
Herbicide Resistant Horseweed Globally
(Conyza canadensis)
#CountryFirstYearSituationActive IngredientsSite of Action
1 BelgiumBelgium 1989 Corn (maize), Nurseries, and Roadsides atrazine 3 Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed35
2 BelgiumBelgium 1998 Nurseries paraquat 3 PSI Electron Diverter (D/22)
61Conyza canadensisHorseweed1145
3 BrazilBrazil 2005 Fruit, Orchards, and Soybean glyphosate 5 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5273
4 Canada (Ontario) CanadaOntario1993 Peaches paraquat 7 PSI Electron Diverter (D/22)
61Conyza canadensisHorseweed48
5 Canada (Ontario) CanadaOntario2010 Soybean glyphosate 7 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5665
6 Canada (Ontario) CanadaOntario2011 Soybean cloransulam-methyl, and glyphosate 7 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5666
7 ChinaChina 2006 Orchards glyphosate 9 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5277
8 Czech RepublicCzech Republic 1987 Corn (maize), Nurseries, Orchards, Pastures, Railways, and Roadsides atrazine 12 Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed83
9 Czech RepublicCzech Republic 2007 Railways glyphosate 12 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5317
10 FranceFrance 1981 Cropland atrazine 17 Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed460
11 FranceFrance 1988 Orchards linuron 17 PSII inhibitor (Ureas and amides) (C2/7)
61Conyza canadensisHorseweed451
12 GreeceGreece 2012 Grapes, and Orchards glyphosate 19 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5692
13 HungaryHungary 2016 Grapes glyphosate 20 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed15070
14 IsraelIsrael 1993 Forests, Industrial sites, and Roadsides atrazine, chlorsulfuron, imazapyr, metribuzin, pyrithiobac-sodium, and sulfometuron-methyl 23 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed109
15 ItalyItaly 2011 Orchards glyphosate 24 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5617
16 JapanJapan 1980 Grapes, Orchards, Railways, and Roadsides paraquat 25 PSI Electron Diverter (D/22)
61Conyza canadensisHorseweed119
17 JapanJapan 2014 Railways glyphosate 25 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed10999
18 PolandPoland 1983 Orchards simazine 33 Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed168
19 PolandPoland 2000 Railways imazapyr 33 ALS inhibitors (B/2)
61Conyza canadensisHorseweed5081
20 PolandPoland 2010 Railways glyphosate 33 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5622
21 PortugalPortugal 2011 Olive glyphosate 34 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed7824
22 South KoreaSouth Korea 2017 Orchards glyphosate 27 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed16077
23 SpainSpain 1987 Corn (maize), Orchards, and Roadsides atrazine, and simazine 38 Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed177
24 SpainSpain 2006 Orchards glyphosate 38 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5319
25 SwitzerlandSwitzerland 1982 Corn (maize), Nurseries, Orchards, Pastures, Railways, and Roadsides atrazine, and simazine 41 Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed203
26 United KingdomUnited Kingdom 1982 Orchards simazine 44 Photosystem II inhibitors (C1/5)
61Conyza canadensisHorseweed362
27 United States (Mississippi) United StatesMississippi1994 Soybean paraquat 45 PSI Electron Diverter (D/22)
61Conyza canadensisHorseweed1109
28 United States (Delaware) United StatesDelaware2000 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5086
29 United States (Tennessee) United StatesTennessee2001 Cotton, and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5122
30 United States (Ohio) United StatesOhio2001 Soybean chlorimuron-ethyl, and cloransulam-methyl 45 ALS inhibitors (B/2)
61Conyza canadensisHorseweed5157
31 United States (Kentucky) United StatesKentucky2001 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5208
32 United States (Ohio) United StatesOhio2002 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5127
33 United States (Indiana) United StatesIndiana2002 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5128
34 United States (Maryland) United StatesMaryland2002 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5129
35 United States (New Jersey) United StatesNew Jersey2002 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5130
36 United States (Michigan) United StatesMichigan2002 Corn (maize), and Soybean chlorimuron-ethyl, and cloransulam-methyl 45 ALS inhibitors (B/2)
61Conyza canadensisHorseweed5172
37 United States (Michigan) United StatesMichigan2002 Blueberries atrazine, diuron, and simazine 45 Multiple Resistance: 2 Sites of Action
Photosystem II inhibitors (C1/5)
PSII inhibitor (Ureas and amides) (C2/7)
61Conyza canadensisHorseweed5173
38 United States (Michigan) United StatesMichigan2002 Blueberries diuron 45 PSII inhibitor (Ureas and amides) (C2/7)
61Conyza canadensisHorseweed5174
39 United States (Missouri) United StatesMissouri2002 Corn (maize), Cotton, and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5260
40 United States (Ohio) United StatesOhio2003 Soybean chlorimuron-ethyl, cloransulam-methyl, and glyphosate 45 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5158
41 United States (Arkansas) United StatesArkansas2003 Cotton glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5187
42 United States (Mississippi) United StatesMississippi2003 Corn (maize), Cotton, Rice, and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5195
43 United States (North Carolina) United StatesNorth Carolina2003 Cotton glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5200
44 United States (Delaware) United StatesDelaware2003 Soybean paraquat 45 PSI Electron Diverter (D/22)
61Conyza canadensisHorseweed5257
45 United States (Pennsylvania) United StatesPennsylvania2003 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5258
46 United States (California) United StatesCalifornia2005 Corn (maize), Fencelines, Grapes, Orchards, Roadsides, and Wheat glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5250
47 United States (Illinois) United StatesIllinois2005 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5276
48 United States (Kansas) United StatesKansas2005 Cotton, and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5308
49 United States (Virginia) United StatesVirginia2005 Corn (maize), and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5559
50 United States (Indiana) United StatesIndiana2005 Soybean chlorimuron-ethyl, and cloransulam-methyl 45 ALS inhibitors (B/2)
61Conyza canadensisHorseweed7836
51 United States (Nebraska) United StatesNebraska2006 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5496
52 United States (Michigan) United StatesMichigan2007 Nurseries glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5312
53 United States (Mississippi) United StatesMississippi2007 Soybean glyphosate, and paraquat 45 Multiple Resistance: 2 Sites of Action
PSI Electron Diverter (D/22)
EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5384
54 United States (West Virginia) United StatesWest Virginia2007 Corn (maize), and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed7774
55 United States (Oklahoma) United StatesOklahoma2009 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5528
56 United States (South Dakota) United StatesSouth Dakota2010 Corn (maize), and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5634
57 United States (Delaware) United StatesDelaware2010 Soybean, and Wheat glyphosate, thifensulfuron-methyl, and tribenuron-methyl 45 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5710
58 United States (Iowa) United StatesIowa2011 Corn (maize), and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed5567
59 United States (Kansas) United StatesKansas2011 Corn (maize), Cotton, Soybean, and Wheat chlorsulfuron, iodosulfuron-methyl-sodium, metsulfuron-methyl, rimsulfuron, thiencarbazone-methyl, thifensulfuron-methyl, and tribenuron-methyl 45 ALS inhibitors (B/2)
61Conyza canadensisHorseweed7806
60 United States (Alabama) United StatesAlabama2013 Corn (maize), Cotton, and Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed7783
61 United States (Wisconsin) United StatesWisconsin2013 Soybean glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed7823
62 United States (Illinois) United StatesIllinois2013 Soybean cloransulam-methyl 45 ALS inhibitors (B/2)
61Conyza canadensisHorseweed7865
63 United States (California) United StatesCalifornia2014 Almonds glyphosate, and paraquat 45 Multiple Resistance: 2 Sites of Action
PSI Electron Diverter (D/22)
EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed9943
64 United States (Montana) United StatesMontana2015 Roadsides glyphosate 45 EPSP synthase inhibitors (G/9)
61Conyza canadensisHorseweed11011
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