International Survey of Herbicide-Resistant Weeds

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(Arctotheca calendula)

PS I Electron Diversion HRAC Group 22 (Legacy D)

Australia, Victoria
Capeweed (Arctotheca calendula) is a dicot weed in the Asteraceae family.  In Victoria this weed first evolved resistance to Group 22 (Legacy D) herbicides in 1986 and infests Alfalfa.   Group 22 (Legacy D) herbicides are known as PS I Electron Diversion (PSI Electron Diversion ).  Research has shown that these particular biotypes are resistant to diquat and they may be cross-resistant to other Group 22 (Legacy D) 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 Jun 06, 2000 )

Common NameCapeweed
SpeciesArctotheca calendula
GroupPS I Electron Diversion HRAC Group 22 (Legacy D)
LocationAustralia, Victoria
Contributors - (Alphabetically)Christopher Preston 
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Christopher Preston
Identified in the state of Victoria.

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Confirmation Tests

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

Genetic studies on HRAC Group 22 resistant Capeweed 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 22 (Legacy D) resistant Capeweed from Victoria please update the database.
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University Of Adelaide - Waite Campus
Crc For Australian Weed Management And School Of Agriculture
Box 2146
Adelaide, 5064, South Australia
Email Christopher Preston


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Victoria have been instrumental in providing you this information. Particular thanks is given to Christopher Preston for providing detailed information.
Herbicide Resistant Capeweed Globally
(Arctotheca calendula)
Herbicide Resistant Capeweed Globally
(Arctotheca calendula)
Drag a column header and drop it here to group by that column
Herbicide Resistant Capeweed Globally
(Arctotheca calendula)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Australia (Victoria) AustraliaVictoria1986 Alfalfa diquat 1 PS I Electron Diversion ( HRAC Group 22 (Legacy D)
21Arctotheca calendulaCapeweed22
2 Australia (South Australia) AustraliaSouth Australia2015 Fallow 2,4-D 1 Auxin Mimics ( HRAC Group 4 (Legacy O)
21Arctotheca calendulaCapeweed15055
3 Australia (Western Australia) AustraliaWestern Australia2020 Wheat diflufenican, glyphosate, and metosulam 1 Multiple Resistance: 3 Sites of Action
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
Phytoene Desaturase inhibitors ( HRAC Group 12 (Legacy F1)
Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)
21Arctotheca calendulaCapeweed19216
Literature about Similar Cases

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