(Arctotheca calendula)

Auxin Mimics HRAC Group 4 (Legacy O)

Australia, South Australia
Capeweed (Arctotheca calendula) is a dicot weed in the Asteraceae family.  In South Australia this weed first evolved resistance to Group 4 (Legacy O) herbicides in 2015 and infests Fallow.   Group 4 (Legacy O) herbicides are known as Auxin Mimics (Auxin Mimics ).  Research has shown that these particular biotypes are resistant to 2,4-D and they may be cross-resistant to other Group 4 (Legacy O) 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 Dec 02, 2016 )

Common NameCapeweed
SpeciesArctotheca calendula
GroupAuxin Mimics HRAC Group 4 (Legacy O)
LocationAustralia, South Australia
Contributors - (Alphabetically)Christopher Preston 
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Confirmation Tests

Greenhouse, and Laboratory 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 4 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 4 (Legacy O) resistant Capeweed from South Australia 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 South Australia 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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PERMISSION MUST BE OBTAINED FIRST if you intend to base a significant portion of a scientific paper on data derived from this site. Citation:
Heap, I.  The International Herbicide-Resistant Weed Database.  Online.  Friday, May 17, 2024 .  Available Copyright © 1993- 2024 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.