<b>HRAC Group 4</b> <font size='2'> (Legacy O) </font> resistant Sonchus oleraceus from Australia, South Australia

International Survey of Herbicide-Resistant Weeds

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Saturday, November 23, 2024

HRAC GROUP 4 (LEGACY O) RESISTANT ANNUAL SOWTHISTLE
(Sonchus oleraceus)

Auxin Mimics HRAC Group 4 (Legacy O)

Australia, South Australia

INTRODUCTION		ANNUAL SOWTHISTLE
Annual Sowthistle (Sonchus oleraceus) 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 Wheat. 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 Apr 15, 2015 )
Common Name	Annual Sowthistle
Species	Sonchus oleraceus
Group	Auxin Mimics HRAC Group 4 (Legacy O)
Herbicides	2,4-D
Location	Australia, South Australia
Year	2015
Situation(s)	Wheat
Contributors - (Alphabetically)	Peter Boutsalis, and Christopher Preston
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Annual Sowthistle biotype with this Annual Sowthistle 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 Annual Sowthistle 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 Annual Sowthistle from South Australia please update the database.

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CONTRIBUTING WEED SCIENTISTS

PETER BOUTSALIS

Postdoctural Fellow/ Consultant University Of Adelaide / Plant Science Consulting Plant And Pest Science 800 N Lindbergh Blvd 02G Adelaide, 5064, South Australia Australia Email Peter Boutsalis

CHRISTOPHER PRESTON

Postdoctural Fellow/ Consultant University Of Adelaide - Waite Campus Crc For Australian Weed Management And School Of Agriculture Box 2146 Adelaide, 5064, South Australia Australia Email Christopher Preston

ACKNOWLEDGEMENTS
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 Peter Boutsalis, and Christopher Preston for providing detailed information.

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Herbicide Resistant Annual Sowthistle Globally
(Sonchus oleraceus)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Australia (Queensland)

1990

Wheat

chlorsulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Australia (Victoria)

2010

Spring Barley, and Wheat

chlorsulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Australia (New South Wales )

2014

Cotton, and Fallow

glyphosate

Inhibition of Enolpyruvyl Shikimate Phosphate Synthase ( HRAC Group 9 (Legacy G)

Australia (South Australia)

2015

Wheat

2,4-D

Auxin Mimics ( HRAC Group 4 (Legacy O)

Australia (South Australia)

2015

Wheat

chlorsulfuron

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Australia (Victoria)

2015

Wheat

2,4-D

Auxin Mimics ( HRAC Group 4 (Legacy O)

Literature about Similar Cases

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Thornby, D. ; Werth, J. ; Walker, S.. 2013. Managing glyphosate resistance in Australian cotton farming: modelling shows how to delay evolution and maintain long-term population control. Crop & Pasture Science 64 : 780 - 790.

Glyphosate resistance is a rapidly developing threat to profitability in Australian cotton farming. Resistance causes an immediate reduction in the effectiveness of in-crop weed control in glyphosate-resistant transgenic cotton and summer fallows. Although strategies for delaying glyphosate resistance and those for managing resistant populations are qualitatively similar, the longer resistance can be delayed, the longer cotton growers will have choice over which tactics to apply and when to apply them. Effective strategies to avoid, delay, and manage resistance are thus of substantial value. We used a model of glyphosate resistance dynamics to perform simulations of resistance evolution in Sonchus oleraceus (common sowthistle) and Echinochloa colona (awnless barnyard grass) under a range of resistance prevention, delaying, and management strategies. From these simulations, we identified several elements that could contribute to effective glyphosate resistance prevention and management strategies. (i) Controlling glyphosate survivors is the most robust approach to delaying or preventing resistance. High-efficacy, high-frequency survivor control almost doubled the useful lifespan of glyphosate from 13 to 25 years even with glyphosate alone used in summer fallows. (ii) Two non-glyphosate tactics in-crop plus two in-summer fallows is the minimum intervention required for long-term delays in resistance evolution. (iii) Pre-emergence herbicides are important, but should be backed up with non-glyphosate knockdowns and strategic tillage; replacing a late-season, pre-emergence herbicide with inter-row tillage was predicted to delay glyphosate resistance by 4 years in awnless barnyard grass. (iv) Weed species' ecological characteristics, particularly seed bank dynamics, have an impact on the effectiveness of resistance strategies; S. oleraceus, because of its propensity to emerge year-round, was less exposed to selection with glyphosate than E. colona, resulting in an extra 5 years of glyphosate usefulness (18 v. 13 years) even in the most rapid cases of resistance evolution. Delaying tactics are thus available that can provide some or many years of continued glyphosate efficacy. If glyphosate-resistant cotton cropping is to remain profitable in Australian farming systems in the long-term, however, growers must adapt to the probability that they will have to deal with summer weeds that are no longer susceptible to glyphosate. Robust resistance management systems will need to include a diversity of weed control options, used appropriately..

Werth, J. ; Boucher, L. ; Thornby, D. ; Walker, S. ; Charles, G.. 2013. Changes in weed species since the introduction of glyphosate-resistant cotton. Crop & Pasture Science 64 : 791 - 798.

Weed management practices in cotton systems that were based on frequent cultivation, residual herbicides, and some post-emergent herbicides have changed. The ability to use glyphosate as a knockdown before planting, in shielded sprayers, and now over-the-top in glyphosate-tolerant cotton has seen a significant reduction in the use of residual herbicides and cultivation. Glyphosate is now the dominant herbicide in both crop and fallow. This reliance increases the risk of shifts to glyphosate-tolerant species and the evolution of glyphosate-resistant weeds. Four surveys were undertaken in the 2008-09 and 2010-11 seasons. Surveys were conducted at the start of the summer cropping season (November-December) and at the end of the same season (March-April). Fifty fields previously surveyed in irrigated and non-irrigated cotton systems were re-surveyed. A major species shift towards Conyza bonariensis was observed. There was also a minor increase in the prevalence of Sonchus oleraceus. Several species were still present at the end of the season, indicating either poor control and/or late-season germinations. These included C. bonariensis, S. oleraceus, Hibiscus verdcourtii and Hibiscus tridactylites, Echinochloa colona, Convolvulus sp., Ipomea lonchophylla, Chamaesyce drummondii, Cullen sp., Amaranthus macrocarpus, and Chloris virgata. These species, with the exception of E. colona, H. verdcourtii, and H. tridactylites, have tolerance to glyphosate and therefore are likely candidates to either remain or increase in dominance in a glyphosate-based system..

Widderick, M. J. ; McLean, A. R. ; Walker, S. R.. 2012. Non-chemical options for managing the seed bank of glyphosate resistant weeds. : 279 - 280.

Glyphosate resistance is becoming a common problem in farming systems of the subtropical cropping region of Australia. Glyphosateresistance has been confirmed in awnless barnyard grass (Echinochloa colona L. (Link)), liverseed grass (Urochloa panicoides P.Beauv.), flaxleaf fleabane (Conyza bonariensis (L.) Cronquist), windmill grass (Chloris truncata R.Br.) and annual ryegrass (Lolium rigidum (Gaud.)) (Preston 2012). As well, common sowthistle (Sonchus oleraceus L.) was identified at high risk of developing glyphosate resistance. To prevent further glyphosate resistance and to improve management of existing glyphosate resistant populations, alternative management tactics for these key weeds are required. This paper reports on the impact of different tillage and stubble treatments on emergence and persistence of awnless barnyard grass and common sowthistle in two experiments located in southern Darling Downs, Queensland..

Werth, J. ; Walker, S. ; Thornby, D. ; Boucher, L.. 2012. Decade of glyphosate-resistant cotton in Australia: what has changed?. Pakistan Journal of Weed Science Research 18 : 671 - 676.

Glyphosate-resistant cotton has been widely adopted in the Australian cotton industry since 2000. Weed management practices are now heavily reliant on glyphosate. Even before the introduction of glyphosate-resistant cotton varieties, glyphosate was increasingly being used. To evaluate any relevant weed issues resulting from this reliance upon glyphosate, we re-surveyed 50 fields previously surveyed in 2001. Results showed a species shift, with Conyza bonariensis and Sonchus oleraceus dominating the flora in cotton systems in 2010-2011. Other glyphosate tolerant species, such as Convolvulus sp., also increased in certain fields. Hibiscus trionum, Ipomea lonchophylla and Echinochloa colona were common in the majority of fields. In 2009, this survey resulted in identification of the first glyphosate resistant weed in Australian cotton systems, E. colona. This population exhibits 3-4 fold resistance to glyphosate. The presence of a glyphosate resistant grass has the potential to increase weed control costs in crop by $40 to $90/ha/yr as well as increasing fallow costs by up to $70/ha/yr. Research was undertaken to determine options for control of C. bonariensis and E. colona in cotton systems, using herbicide alternatives to glyphosate. This paper describes weed management challenges for the Australian cotton industry and explores chemical management options for glyphosate tolerant and resistant weeds..

Werth, J. ; Walker, S. ; Thornby, D. ; Boucher, L.. 2011. A decade of glyphosate-resistant cotton in Australia: what has changed?. : 571 - 575.

Glyphosate-resistant cotton has been widely adopted in the Australian cotton industry since 2000. Weed management practices are now heavily reliant on glyphosate. Even before the introduction of glyphosate-resistant cotton varieties, glyphosate was increasingly being used. To evaluate any relevant weed issues resulting from this reliance upon glyphosate, we re-surveyed 50 fields previously surveyed in 2001. Results showed a species shift, with Conyza bonariensis and Sonchus oleraceus dominating the flora in cotton systems in 2010-2011. Other glyphosate tolerant species, such as Convolvulus sp., also increased in certain fields. Hibiscus trionum, Ipomea lonchophylla and Echinochloa colona were common in the majority of fields. In 2009, this survey resulted in identification of the first glyphosate resistant weed in Australian cotton systems, E. colona. This population exhibits 3-4 fold resistance to glyphosate. The presence of a glyphosate resistant grass has the potential to increase weed control costs in crop by $40 to $90/ha/yr as well as increasing fallow costs by up to $70/ha/yr. Research was undertaken to determine options for control of C. bonariensis and E. colona in cotton systems, using herbicide alternatives to glyphosate. This paper describes weed management challenges for the Australian cotton industry and explores chemical management options for glyphosate tolerant and resistant weeds..

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