International Survey of Herbicide-Resistant Weeds

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Status of Herbicide Resistance in Louisiana - Daniel Stephenson : January, 2014

Glyphosate-resistance, particularly GR Palmer amaranth, continues to be the most observed herbicide-resistant weed species in Louisiana crops. In 2013, GR Palmer amaranth was documented in 4 additional parishes, bringing the total number of GR Palmer amaranth infested parishes to 18. These 18 include most if not all parishes in the Mississippi River, Macon Ridge, Red River regions of Louisiana. In addition, GR Palmer amaranth is highly suspected in the Prairie region of Louisiana. Fortunately, GR Palmer amaranth populations in these parishes are not widespread. Louisiana growers are utilizing practices, such as residual herbicides and hand-removal, to mitigate its spread and manage existing populations. Glyphosate-resistant johnsongrass was documented in one additional parish in Louisiana, but, GR johnsongrass is not a widespread issue. Halosulfuron-resistant rice flatsedge and imazethapyr-resistant barnyardgrass has not been observed on a widespread basis yet. We continue to inform Louisiana producers of our findings so they can implement mitigation practices.

Herbicide Resistant Weeds in Louisiana, United States.
#YearSpeciesSite of ActionActivesContacts
1 1045Common cocklebur1992Xanthium strumarium
Common cocklebur
United States
(Louisiana)
LouisianaLA Nucleic acid inhibitors (Z/17) Nucleic acid inhibitors (Z/17) MSMA Dearl Sanders
2 1046Barnyardgrass1995Echinochloa crus-galli var. crus-galli
Barnyardgrass
United States
(Louisiana)
LouisianaLA PSII inhibitors - Serine 264 Binders (C1 C2/7) PSII inhibitors - Serine 264 Binders (C1 C2/7) propanil Dearl Sanders
3 1182Itchgrass1997Rottboellia cochinchinensis (=R. exaltata)
Itchgrass
United States
(Louisiana)
LouisianaLA Inhibition of Acetyl CoA Carboxylase (A/1) Inhibition of Acetyl CoA Carboxylase (A/1) fluazifop-butyl Dearl Sanders
4 1044Johnsongrass1997Sorghum halepense
Johnsongrass
United States
(Louisiana)
LouisianaLA Inhibition of Acetyl CoA Carboxylase (A/1) Inhibition of Acetyl CoA Carboxylase (A/1) clethodim, fluazifop-butyl Dearl Sanders, Donnie Miller
5 1180Barnyardgrass1998Echinochloa crus-galli var. crus-galli
Barnyardgrass
United States
(Louisiana)
LouisianaLA Auxin Mimics (O/4) Auxin Mimics (O/4) quinclorac Dearl Sanders
6 5565Amazon Sprangletop2009Leptochloa panicoides
Amazon Sprangletop
United States
(Louisiana)
Louisiana  Inhibition of Acetyl CoA Carboxylase (A/1) Inhibition of Acetyl CoA Carboxylase (A/1) cyhalofop-butyl, fenoxaprop-ethyl Jason Norsworthy
7 5494Palmer Amaranth2010Amaranthus palmeri
Palmer Amaranth
United States
(Louisiana)
Louisiana  Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) glyphosate Daniel Stephenson
8 5522Johnsongrass2010Sorghum halepense
Johnsongrass
United States
(Louisiana)
Louisiana  Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) glyphosate James Griffin
9 7785Rice Flatsedge2013Cyperus iria
Rice Flatsedge
United States
(Louisiana)
Louisiana  Inhibition of Acetolactate Synthase (B/2) Inhibition of Acetolactate Synthase (B/2) halosulfuron-methyl Daniel Stephenson
10 7786Barnyardgrass2013Echinochloa crus-galli var. crus-galli
Barnyardgrass
United States
(Louisiana)
Louisiana  Inhibition of Acetolactate Synthase (B/2) Inhibition of Acetolactate Synthase (B/2) imazethapyr Daniel Stephenson, Eric Webster
11 8898Italian Ryegrass2014Lolium perenne ssp. multiflorum
Italian Ryegrass
United States
(Louisiana)
Louisiana  Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) glyphosate Daniel Stephenson
12 11005Tall Waterhemp2015Amaranthus tuberculatus (=A. rudis)
Tall Waterhemp
United States
(Louisiana)
Louisiana  Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) Inhibition of Enolpyruvyl Shikimate Phosphate Synthase (G/9) glyphosate Daniel Stephenson
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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Monday, November 29, 2021 .  Available  www.weedscience.org
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