<b>HRAC Group 2</b> <font size='2'> (Legacy B) </font> resistant Chamaesyce maculata from United States, Georgia

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 2 (LEGACY B) RESISTANT SPOTTED SPURGE
(Chamaesyce maculata)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

United States, Georgia

INTRODUCTION		SPOTTED SPURGE
Spotted Spurge (Chamaesyce maculata) is a dicot weed in the Euphorbiaceae family. In Georgia this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2014 and infests Turf. Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ). Research has shown that these particular biotypes are resistant to metsulfuron-methyl and they may be cross-resistant to other Group 2 (Legacy B) 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 May 02, 2016 )
Common Name	Spotted Spurge
Species	Chamaesyce maculata
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	metsulfuron-methyl
Location	United States, Georgia
Year	2014
Situation(s)	Turf
Contributors - (Alphabetically)	Scott Mcelroy
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Spotted Spurge biotype with this Spotted Spurge 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 2 resistant Spotted Spurge 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

Studies on the mechanism of resistance of Group 2 (Legacy B) resistant Spotted Spurge from Georgia indicate that resistance is due to an altered target site. There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature

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 2 (Legacy B) resistant Spotted Spurge from Georgia please update the database.

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CONTRIBUTING WEED SCIENTISTS

SCOTT MCELROY

Assistant Professor Auburn University Depart. Of Agronomy And Soils 201 Funchess Hall Auburn, 36830, Alabama United States Email Scott Mcelroy Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Georgia have been instrumental in providing you this information. Particular thanks is given to Scott Mcelroy for providing detailed information.

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Herbicide Resistant Spotted Spurge Globally
(Chamaesyce maculata)

Country

FirstYear

Situation

Active Ingredients

Site of Action

United States (Georgia)

2014

Turf

metsulfuron-methyl

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

Literature about Similar Cases

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McCullough, P. E., J. S. McElroy, J. Yu, H. Zhang, T. B. Miller, S. Chen, C. R. Johnston, and M. A. Czarnota. 2016. ALS-resistant spotted spurge (Chamaesyce maculata) confirmed in Georgia. Weed Science 64 : 216 - 222.

Metsulfuron is used for POST control of spotted spurge in many warm-season turfgrasses. A suspected resistant (R) biotype of spotted spurge was collected from turfgrass in Georgia with a history of exclusive metsulfuron use. Research was conducted to evaluate the resistance level of this biotype to metsulfuron, efficacy of other mechanisms of action for control, and the molecular basis for resistance. Compared with a susceptible (S) biotype, the R biotype required >90 and >135 times greater metsulfuron rates to reach 50% injury and reduce biomass 50% from the nontreated, respectively. The R biotype was also resistant to trifloxysulfuron but was injured equivalent to the S biotype from dicamba, glyphosate, and triclopyr. Gene sequencing of the R biotype revealed a Trp₅₇₄ to Leu substitution that has conferred resistance to acetolactate synthase (ALS) inhibitors in previous research. This is the first report of ALS resistance in spotted spurge. More importantly, this is the first report of a herbicide-resistant broadleaf weed from a turfgrass system in the United States..

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