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

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

United States, Georgia

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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  Edit this Case  |  Add New Case of Resistance  |  Add Note

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.   Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  Help

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.

Herbicide Resistant Spotted Spurge Globally (Chamaesyce maculata) Herbicide Resistant Spotted Spurge Globally (Chamaesyce maculata) Drag a column header and drop it here to group by that column Herbicide Resistant Spotted Spurge Globally (Chamaesyce maculata) # Country Country StateName FirstYear Situation Active Ingredients CountryID Site of Action WeedID Species CommonName ResistID 1 United States (Georgia) United States Georgia 2014 Turf metsulfuron-methyl 45 Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B) 332 Chamaesyce maculata Spotted Spurge 13035

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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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Tuesday, April 16, 2024 .  Available  www.weedscience.org
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