Herbicide Resistant Weeds

GROUP B/2 RESISTANT PALMER AMARANTH (Amaranthus palmeri)
USA: Arkansas

Thursday, September 02, 2010

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Palmer Amaranth

1.	Introduction
2.	Level of Infestation
3.	Quick Statistics
4.	Notes about this biotype
5.	Academic Aspects
6.	R Palmer Amaranth Globally
7.	Fact Sheets and Literature
8.	Contributing Weed Scientists
9.	Acknowledgements
10.	Where to now?

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Introduction

Level of Infestation

Palmer Amaranth (Amaranthus palmeri) is a dicot weed in the Amaranthaceae family. In Arkansas this weed first evolved resistance to Group B/2 herbicides in 1994 and infests soybean. Group B/2 herbicides are known as ALS inhibitors (Inhibition of acetolactate synthase ALS (acetohydroxyacid synthase AHAS)). Research has shown that these particular biotypes are resistant to chlorimuron-ethyl, diclosulam, imazaquin, imazethapyr, and pyrithiobac-Na and they may be cross-resistant to other Group B/2 herbicides.

Local weed scientists estimate that Group B/2 resistant Palmer Amaranth in Arkansas infests 101-500 sites and the number of sites are increasing. They also estimate that there are 10001-100000 acres infested with Group B/2 resistant Palmer Amaranth.

The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their mode of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS ( last updated Nov 20, 2009 )
Common Name	Palmer Amaranth
Species	Amaranthus palmeri
Group	ALS inhibitors (B/2)
Herbicides	chlorimuron-ethyl, diclosulam, imazaquin, imazethapyr, and pyrithiobac-Na
Location	USA, Arkansas
Year	1994
Situation(s)	soybean
Sites	101-500
Acres Infested	10001-100000
Contributors	Nilda R. Burgos, and Ronald Talbert (Retired)
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NOTES ABOUT THIS BIOTYPE

AREAS FOUND

Ronald Talbert (Retired)

Lawrence, Logan, Woodruff.

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GENERAL

Ronald Talbert (Retired)

Cross resistant to chlorimuron, pyrithiobac, diclosulam - ALS enzyme assay. The resistant biotype of A. palmeri is 273-fold more resistant to imazaquin and showed 43-, 45-, and 65-fold resistance to diclosulam, pyrithiobac, and chlorimuron, respectively. Resistance to imazaquin and cross-resistance to other ALS inhibitors were several magnitudes higher at the enzyme level.

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Palmer Amaranth biotype with this Palmer Amaranth 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

The genetic basis of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the genetic inheritance of this biotype please update the database.

Mechanism of Resistance

Studies on the mechanism of resistance of Group B/2 resistant Palmer Amaranth from Arkansas 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 B/2 resistant Palmer Amaranth from Arkansas please update the database.

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HERBICIDE RESISTANT PALMER AMARANTH GLOBALLY
#	Country	Year	Sites	Acres	Mode of Action
1.	USA (South Carolina)	1989	501-1000	10001-100000	Dinitroanilines and others (K1/3)
2.	USA (Kansas)	1991	501-1000	10001-100000	ALS inhibitors (B/2)
3.	USA (Texas)	1993	2-5	11-50	Photosystem II inhibitors (C1/5)
4.	USA (Arkansas)	1994	101-500	10001-100000	ALS inhibitors (B/2)
5.	USA (Kansas)	1995	unknown	unknown	Photosystem II inhibitors (C1/5)
6.	USA (North Carolina)	1995	11-50	1001-10000	ALS inhibitors (B/2)
7.	USA (Texas)	1995	2-5	501-1000	Photosystem II inhibitors (C1/5)
8.	USA (Texas)	1995	2-5	501-1000	Photosystem II inhibitors (C1/5)
9.	USA (South Carolina)	1997	2-5	101-500	ALS inhibitors (B/2)
10.	USA (Georgia)	2000	2-5	101-500	ALS inhibitors (B/2)
11.	USA (Georgia)	2005	101-500	100001-1000000	Glycines (G/9)
12.	USA (North Carolina)	2005	unknown	100001-1000000	Glycines (G/9)
13.	USA (Arkansas)	2006	1001-10000	100001-1000000	Glycines (G/9)
14.	USA (Tennessee)	2006	1001-10000	10001-100000	ALS inhibitors (B/2)
15.	USA (Tennessee)	2006	2-5	101-500	Glycines (G/9)
16.	USA (Tennessee)	2006	1001-10000	100001-1000000	Glycines (G/9)
17.	USA (New Mexico)	2007	2-5	51-100	Glycines (G/9)
18.	USA (Mississippi) Multiple Resistance	2008	unknown	unknown	ALS inhibitors (B/2) Glycines (G/9)
19.	USA (Florida)	2008	11-50	1001-10000	ALS inhibitors (B/2)
20.	USA (Alabama)	2008	1	51-100	Glycines (G/9)
21.	USA (Missouri)	2008	6-10	1001-10000	Glycines (G/9)

FACT SHEETS AND OTHER LITERATURE	Format
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Scientific Abstracts on Herbicide Resistant Amaranthus palmeri
Transferal of herbicide resistance traits from Amaranthus palmeri to Amaranthus rudis.
Wetzel, D. K., M. Horak J., D. Skinner Z., and P. Kulakow A. 1999. Transferal of herbicide resistance traits from Amaranthus palmeri to Amaranthus rudis. Weed Science. 47: 538-543.
Palmer amaranth (Amaranthus palmeri) and common waterhemp (Amaranthus rudis) resistance to selected ALS-inhibiting herbicides.
Sprague, C. L., E. W. Stoller, L. M. Wax, and M. J. Horak. 1997. Palmer amaranth (Amaranthus palmeri) and common waterhemp (Amaranthus rudis) resistance to selected ALS-inhibiting herbicides. Weed Science. 45: 192-197.
Control and cross-resistance of an acetolactate synthase inhibitor-resistant Palmer amaranth (Amaranthus palmeri) biotype.
Gaeddert, J. W., D. E. Peterson, and M. J. Horak. 1997. Control and cross-resistance of an acetolactate synthase inhibitor-resistant Palmer amaranth (Amaranthus palmeri) biotype. Weed Technology. 11: 132-137.
Biotypes of Palmer amaranth (Amaranthus palmeri) and common waterhemp (Amaranthus rudis) are resistant to imazethapyr and thifensulfuron.
Horak, M. J. and D. E. Peterson. 1995. Biotypes of Palmer amaranth (Amaranthus palmeri) and common waterhemp (Amaranthus rudis) are resistant to imazethapyr and thifensulfuron. Weed Technology. 9: 192-195.
The history and present status of herbicide-resistant weed biotypes [Eleusine indica, Amaranthus palmeri and Xanthium strumarium] in South Carolina cotton.
Murdock, E. C., A. C. York, and B. J. Gossett. 1993. The history and present status of herbicide-resistant weed biotypes [Eleusine indica, Amaranthus palmeri and Xanthium strumarium] in South Carolina cotton. Proceedings, Beltwide Cotton Conferences, 10-14 January 1993, New Orleans, Louisiana, USA. : 1507.
Resistance of Palmer amaranth (Amaranthus palmeri) to the dinitroaniline herbicides.
Gossett, B. J., E. C. Murdock, and J. E. Toler. 1992. Resistance of Palmer amaranth (Amaranthus palmeri) to the dinitroaniline herbicides. Weed Technology. 6: 587-591.

CONTRIBUTING WEED SCIENTISTS

NILDA R. BURGOS	Edit
Associate Professor - Weed Physiology University of Arkansas, Fayetteville Crop, Soil and Environmental Sciences 1366 W. Altheimer Drive Fayetteville, 72704, Arkansas USA Email Nilda R. Burgos

RONALD TALBERT (RETIRED)	Edit
Retired from University of ArkansasArkansas USA Email Ronald Talbert (Retired)

Acknowledgements

Where to now?

The Herbicide Resistance Action Committee, The North American Herbicide Resistance Action Committee, the Weed Science Society of America, and weed scientists in Arkansas have been instrumental in providing you this information. Particular thanks is given to Nilda R. Burgos, and Ronald Talbert (Retired) for providing detailed information.

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