<b>HRAC Group 4</b> <font size='2'> (Legacy O) </font> resistant Carduus nutans from New Zealand

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 4 (LEGACY O) RESISTANT MUSK THISTLE
(Carduus nutans)

Auxin Mimics HRAC Group 4 (Legacy O)

New Zealand

INTRODUCTION		MUSK THISTLE
Musk Thistle (Carduus nutans) is a dicot weed in the Asteraceae family. In New Zealand this weed first evolved resistance to Group 4 (Legacy O) herbicides in 1981 and infests Pastures. 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.

QUIK STATS (last updated Jun 06, 2000 )
Common Name	Musk Thistle
Species	Carduus nutans
Group	Auxin Mimics HRAC Group 4 (Legacy O)
Herbicides	2,4-D
Location	New Zealand
Year	1981
Situation(s)	Pastures
Contributors - (Alphabetically)	Kerry Harrington, and Anis Rahman
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NOTES ABOUT THIS BIOTYPE

AREAS FOUND

Anis Rahman

Waikato, Hawkes Bay, Manawatu, etc.

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CONTROL STRATEGIES

Anis Rahman

This thistle is controlled by adding clopyralid to the phenoxy herbicide which causes severe damage to clovers in pasture. True cost is not shown as there is damage to the clover.

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GENERAL

Anis Rahman

This weed is a problem in pastures. Our pastures have two components viz. ryegrass and clovers. It is difficult to find herbicides selective enough to both components that will control the thistles. Also resistant to MCPA.

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ACADEMIC ASPECTS

Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Musk Thistle biotype with this Musk Thistle 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 HRAC Group 4 resistant Musk Thistle 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 Musk Thistle from New Zealand please update the database.

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CONTRIBUTING WEED SCIENTISTS

KERRY HARRINGTON

Associate Professor in Weed Science Massey University School of Agriculture Private Bag 11-222 Palmerston North, 4442, Manawatu New Zealand Email Kerry Harrington Web : Web Site Link

ANIS RAHMAN

Associate Professor in Weed Science Ruakura Agricultural Centre Ag. Research 3205 College Ave Hamilton, 4442, Manawatu New Zealand Email Anis Rahman Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in New Zealand have been instrumental in providing you this information. Particular thanks is given to Kerry Harrington, and Anis Rahman for providing detailed information.

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Herbicide Resistant Musk Thistle Globally
(Carduus nutans)

Country

FirstYear

Situation

Active Ingredients

Site of Action

New Zealand

1981

Pastures

2,4-D

Auxin Mimics ( HRAC Group 4 (Legacy O)

Literature about Similar Cases

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Harrington, K. C. ; Woolley, D. J.. 2006. Investigations of how phenoxy-resistant Carduus nutans biotypes survive herbicide spraying. New Zealand Journal of Agricultural Research 49 : 465 - 474.

Biotypes of nodding thistle (Carduus nutans) have developed within New Zealand that require over six times the normal rate of MCPA, MCPB or 2,4-D to kill them. Radiolabelled 2,4-D was applied to both resistant and susceptible nodding thistle plants to investigate the mechanism of resistance. There was no difference in penetration of the 2,4-D into the foliage of the resistant and susceptible plants. However some minor differences in translocation were detected, with the 2,4-D apparently less mobile within the resistant plants. These differences were variable and did not fully explain the resistance. Significantly more radioactivity was released from the roots of susceptible plants. There were also small but significant differences in the quantities of radioactivity that could be removed from within the treated plants by ethanol, suggesting more binding within susceptible plants. Significant differences were detected in rates of metabolism of 2,4-D within the root systems. More radioactivity was present as water-soluble compounds in the resistant plants than the susceptible ones. Of the ether-soluble components extracted, about 14 times more 2,4-D was estimated to be present in susceptible plants than in resistant plants, with chromatography suggesting that compounds in the resistant plants were metabolites of 2,4-D..

Bonner, K. I. ; Rahman, A. ; James, T. K. ; Nicholson, K. S. ; Wardle, D. A.. 1998. Relative intra-species competitive ability of nodding thistle biotypes with varying resistance to the herbicide 2,4-D. New Zealand Journal of Agricultural Research 41 : 291 - 297.

In field studies conducted in New Zealand, eight biotypes of nodding thistle (Carduus nutans) known to differ in resistance to the herbicide 2,4-D were selected and their relative competitive abilities were evaluated during vegetative growth in terms of their effects on the growth of the other biotypes, growth response to the other biotypes, and growth and seedling emergence responses to pre-established swards of perennial ryegrass (Lolium perenne). Although biotypes differed in terms of competitive ability for each of these measures, there was no detectable agreement between any pair of measures across the eight biotypes. None of the measures of competitive ability was significantly correlated with herbicide resistance across the biotypes. The results showed no clear causative relationship between competitive ability as measured in this experiment and herbicide resistance. It was concluded that since resistant populations were apparently of comparable competitive ability to susceptible ones, cessation of herbicide use is unlikely to be followed by a significant loss of resistant individuals from a population..

Harrington, K. C.. 1996. Herbicide management and thistle control - how to avoid resistance. Plant Protection Quarterly 11 : 273 - 275.

Populations of nodding thistle (Carduus nutans) have been located in Hawkes Bay (New Zealand) which require six times more MCPA than normal to obtain adequate control. Such populations are known to exist on at least 12 properties in Hawkes Bay and Waikato. A comparison of past spraying practices on these properties and farms where resistance has not developed identified that resistance has occurred due to more frequent use of phenoxy herbicides on the former properties. Cross-resistance exists within these populations to 2,4-D, MCPA and MCPB. Thus such thistles can only be controlled by adding clopyralid to one of these herbicides, which is damaging to pasture legumes. Work with radiolabelled MCPA has shown that resistance is due to an increased rate of herbicide degradation within the plant rather than reduced uptake, so adding surfactants to the herbicide will not overcome the resistance. Based on research results from a range of sources, recommendations for the control of such herbicide-resistant species are made..

James, T. K. ; Rahman, A. ; Sanders, P. ; Cliffe, A.. 1995. Response of different nodding thistle (Carduus nutans) populations to herbicides. : 252 - 255.

Resistance to phenoxy herbicides in nodding thistle (Carduus nutans) is becoming a major concern in pastures in New Zealand. To ascertain the extent of resistance, C. nutans was collected from several farms (10 sites) in Waikato, New Zealand, with a range of histories using phenoxy herbicides, and seeds grown from these populations were treated with 2,4-D to determine their response. There were no apparent morphological differences in the appearance of C. nutans grown from seed collected from the 10 sites, but their response to 2,4-D varied. Only plants from 1 site (which had not been treated with 2,4-D for 10-15 years) were completely susceptible. Sites where 2,4-D had been used more recently had larger numbers of control failures. The site that historically had the most intensive use of 2,4-D (every year for the last 10 years) contained plants exhibiting resistance. In a 2nd trial using a resistant and susceptible population of C. nutans, it was found that when dicamba was used with 2,4-D, the overall level of control was not adequate for farming situations. A 3rd trial showed that even large, phenoxy-resistant C. nutans could be controlled by herbicides (2,4-D + metsulfuron, 2,4-D + picloram, 2,4-D + clopyralid and metsulfuron), but severe pasture damage usually resulted. It was concluded that the resistance problem in Waikato may be widespread. The use of herbicides or their combinations to control C. nutans needs to be judicious and alternative methods of application, such as spot treatment or carpet wipers, should be considered..

Rahman, A. ; James, T. K. ; Sanders, P.. 1994. Control of phenoxy herbicide resistant nodding thistle (Carduus nutans) in pasture. : 68 - 74.

The effectiveness of some phenoxy herbicides and their mixtures, and some sulfonylurea herbicides on a phenoxy-resistant biotype of nodding thistle was evaluated in two pot experiments during 1990-92 and two field trials at Maungatautari, Waikato, in 1991. High tolerance to both 2,4-D and MCPA was confirmed but this varied between the resistant populations and with plant age. Use of different formulations and adjuvants gave improved but variable results. Effective control was obtained with mixtures of clopyralid, mecoprop or dicamba with 2,4-D. Mecoprop and clopyralid were also effective when used alone. No cross resistance to sulfonylurea herbicides was found as they were equally phytotoxic to both biotypes. All these options lacked selectively in pastures but a mixture of 2,4-D with clopyralid or dicamba could be used as a short term measure to assist the integrated management of problem thistle populations..

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