<b>HRAC Group 5</b> <font size='2'> (Legacy C1 C2) </font> resistant Alopecurus myosuroides from Switzerland

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 5 (LEGACY C1 C2) RESISTANT BLACKGRASS
(Alopecurus myosuroides)

PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)

Switzerland

INTRODUCTION		BLACKGRASS
Blackgrass (Alopecurus myosuroides) is a monocot weed in the Poaceae family. In Switzerland this weed first evolved resistance to Group 5 (Legacy C1 C2) herbicides in 1997 and infests Wheat, and Winter barley. Group 5 (Legacy C1 C2) herbicides are known as PSII inhibitors - Serine 264 Binders (Inhbition of Photosynthesis at PSll - Serine 264 Binders ). Research has shown that these particular biotypes are resistant to chlorotoluron, and isoproturon and they may be cross-resistant to other Group 5 (Legacy C1 C2) 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 Aug 11, 2021 )
Common Name	Blackgrass
Species	Alopecurus myosuroides
Group	PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)
Herbicides	chlorotoluron, and isoproturon
Location	Switzerland
Year	1997
Situation(s)	Wheat, and Winter barley
Contributors - (Alphabetically)	Christian Bohren, and Fred Tschuy
Edit this Case \| Add New Case of Resistance \| Add Note

NOTES ABOUT THIS BIOTYPE

GENERAL

Christian Bohren

A field trial 1997 at Grenchen (SO): Winterwheat, field treatments: - 1500 g a.i. Isoproturon/ha - untreated : From each plot (4rep) 20 samples of seeds of single ALOMY plant have been collected. In the greenhouse all seeds were planted into small pots; half of them treated in 2-3 leaf st. with 2000 g a.i. IPU/ha, the other half treated with 240 g a.i. Fenoxapropethyl/ha Results of greenhouse trial in 1998: field treatment IPU --> 33 % surviving IPU treatment in greenhouse field nontreated --> 25 % surviving IPU treatment in greenhouse 0 % surviving fenoxaprop treatment in greenhouse. Farmers observed a better efficacy of IPU against grass weeds in mixture with other herbicides (e.g. carfentrazone, triasulfuron, diflufenican).

Edit this Note | Add New Note

SERIOUSNESS

Christian Bohren

ALOMY is found in large numbers where wheat is grown and IPU is used intensively. In CH are more areas with reduced efficacy of IPU against ALOMY: - near Grenchen (resistance confirmed) - near Frick (not confirmed) - near Andelfingen (not confirmed) and others It is not easy to say in which areas IPU resistance of ALOMY is present, but it is easy to say that efficacy of IPU against ALOMY is decreasing. Since IPU is still in use the infested area is probably increasing

Edit this Note | Add New Note

ACADEMIC ASPECTS

Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible Blackgrass biotype with this Blackgrass 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 5 resistant Blackgrass 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 5 (Legacy C1 C2) resistant Blackgrass from Switzerland indicate that resistance is due to enhanced metabolism. 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 5 (Legacy C1 C2) resistant Blackgrass from Switzerland please update the database.

Edit Case | Add Note | Add Article | Add New Case |

CONTRIBUTING WEED SCIENTISTS

CHRISTIAN BOHREN

Swiss Federal Research Station For Plant Production Service De Malherbologie 119 Extension Hall Nyon 1, CH 1260 Switzerland Email Christian Bohren

FRED TSCHUY

Technical scientist Agroscope Institute for Plant Production Plant Protection for Field Crops and Viticulture/Oenology Route de Duillier 50 Nyon, CH-1260, Vaud Switzerland Email Fred Tschuy Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Switzerland have been instrumental in providing you this information. Particular thanks is given to Christian Bohren, and Fred Tschuy for providing detailed information.

Drag a column header and drop it here to group by that column

Herbicide Resistant Blackgrass Globally
(Alopecurus myosuroides)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Belgium

1996

Winter wheat

clodinafop-propargyl, and fenoxaprop-ethyl

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Belgium

1996

Wheat

isoproturon

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Belgium

1996

Winter wheat

atrazine, chlorotoluron, clodinafop-propargyl, fenoxaprop-ethyl, flupyrsulfuron-methyl-Na, pendimethalin, and propaquizafop

Multiple Resistance: 4 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
Inhibition of Microtubule Assembly ( HRAC Group 3 (Legacy K1)

Czech Republic

2008

Wheat

chlorsulfuron

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

Denmark

2001

Winter wheat

fenoxaprop-ethyl

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Denmark

2001

Winter wheat

clodinafop-propargyl, cycloxydim, fenoxaprop-ethyl, florasulam, flupyrsulfuron-methyl-Na, iodosulfuron-methyl-Na, mesosulfuron-methyl, pendimethalin, and pyroxsulam

Multiple Resistance: 3 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
Inhibition of Microtubule Assembly ( HRAC Group 3 (Legacy K1)

France

1993

Wheat

clodinafop-propargyl, cycloxydim, diclofop-methyl, fenoxaprop-ethyl, haloxyfop-methyl, and sethoxydim

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

France

2003

Wheat

clodinafop-propargyl, diclofop-methyl, fenoxaprop-ethyl, iodosulfuron-methyl-Na, mesosulfuron-methyl, and sethoxydim

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

France

2006

Wheat

imazamethabenz-methyl, iodosulfuron-methyl-Na, and mesosulfuron-methyl

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

France

2020

Cereals, and Rapeseed

flufenacet, and prosulfocarb

Very Long-Chain Fatty Acid Synthesis inhibitors ( HRAC Group 15 (Legacy K3 N)

France

2022

Wheat

glyphosate

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

Germany

1983

Sugar beets, and Wheat

chlorotoluron, fenoxaprop-ethyl, and isoproturon

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Germany

2001

Wheat

flupyrsulfuron-methyl-Na

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

Germany

2003

Sugar beets, and Winter wheat

clethodim, cycloxydim, fenoxaprop-ethyl, and fluazifop-butyl

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Germany

2007

Wheat

chlorotoluron, fenoxaprop-ethyl, flufenacet, isoproturon, mesosulfuron-methyl, and pinoxaden

Multiple Resistance: 4 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)
Very Long-Chain Fatty Acid Synthesis inhibitors ( HRAC Group 15 (Legacy K3 N)

Germany

2009

Cereals

cycloxydim, fenoxaprop-ethyl, flupyrsulfuron-methyl-Na, mesosulfuron-methyl, and pinoxaden

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Ireland

2021

Wheat

cycloxydim, iodosulfuron-methyl-Na, mesosulfuron-methyl, and propaquizafop

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Israel

1979

Roadsides

methabenzthiazuron

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Italy

2009

Durum wheat

clodinafop-propargyl, fenoxaprop-ethyl, and pinoxaden

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Netherlands

1989

Wheat

chlorotoluron

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Netherlands

1996

Winter wheat

chlorotoluron, clodinafop-propargyl, fenoxaprop-ethyl, and isoproturon

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Netherlands

1999

Winter wheat

clodinafop-propargyl, cycloxydim, fenoxaprop-ethyl, and penoxsulam

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Netherlands

2010

Winter wheat

florasulam, iodosulfuron-methyl-Na, mesosulfuron-methyl, and pyroxsulam

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

Poland

2010

Winter wheat

iodosulfuron-methyl-Na, and mesosulfuron-methyl

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

Poland

2011

Winter wheat

fenoxaprop-ethyl, and pinoxaden

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Poland

2012

Winter wheat

fenoxaprop-ethyl, iodosulfuron-methyl-Na, mesosulfuron-methyl, pinoxaden, and sulfometuron-methyl

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Spain

1991

Wheat

chlorotoluron

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Spain

2015

Canola, Faba beans, Peas, Wheat, and Winter barley

chlorotoluron, clodinafop-propargyl, cloransulam-methyl, iodosulfuron-methyl-Na, isoproturon, mesosulfuron-methyl, and pinoxaden

Multiple Resistance: 3 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Sweden

2011

Winter wheat

clodinafop-propargyl, cycloxydim, and fenoxaprop-ethyl

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Sweden

2011

Wheat

fenoxaprop-ethyl, flupyrsulfuron-methyl-Na, prosulfocarb, and pyroxsulam

Multiple Resistance: 3 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)
Very Long-Chain Fatty Acid Synthesis inhibitors ( HRAC Group 15 (Legacy K3 N)

Sweden

2014

Spring wheat, Winter barley, and Winter wheat

cycloxydim, fenoxaprop-ethyl, flupyrsulfuron-methyl-Na, iodosulfuron-methyl-Na, mesosulfuron-methyl, and pyroxsulam

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Switzerland

1997

Wheat, and Winter barley

chlorotoluron, and isoproturon

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

Switzerland

2019

Wheat, and Winter barley

chlorotoluron, iodosulfuron-methyl-Na, mesosulfuron-methyl, and quizalofop-ethyl

Turkey

2001

Wheat

clodinafop-propargyl

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

Turkey

2008

clodinafop-propargyl, and pyroxsulam

Multiple Resistance: 2 Sites of Action
Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)
Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

United Kingdom

1982

Canola, Cereals, and Wheat

clethodim, clodinafop-propargyl, cycloxydim, diclofop-methyl, fenoxaprop-ethyl, fluazifop-butyl, pinoxaden, quizalofop-ethyl, and sethoxydim

Inhibition of Acetyl CoA Carboxylase ( HRAC Group 1 (Legacy A)

United Kingdom

1982

Cereals

chlorotoluron, and isoproturon

PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2)

United Kingdom

1984

Wheat

chlorsulfuron, flupyrsulfuron-methyl-Na, imazamethabenz-methyl, iodosulfuron-methyl-Na, mesosulfuron-methyl, propoxycarbazone-Na, and pyroxsulam

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

United Kingdom

1987

Wheat

pendimethalin

Inhibition of Microtubule Assembly ( HRAC Group 3 (Legacy K1)

Literature about Similar Cases

1 2 3 4 5 6 ...

Page size:

select

Page: of 48

Items 1 to 5 of 237

Rosenhauer, M. ; Jaser, B. ; Felsenstein, F. G. ; Petersen, J.. 2013. Development of target-site resistance (TSR) in Alopecurus myosuroides in Germany between 2004 and 2012. Journal of Plant Diseases and Protection 120 : 179 - 187.

Alopecurus myosuroides is one of the most important grass weeds on arable land in Germany. For many years, it has developed herbicide-resistant populations. ACCase- and ALS-inhibiting herbicides, in particular, have lost significant efficacy. Two different mechanisms are commonly known to confer resistance to herbicides: target-site resistance (TSR) and non-target-site resistance (NTSR). In Germany, onlyapproximately 5 to 10% of the herbicide-resistant black-grasspopulations have been reported to show TSR so far. To quantify the status and the distribution of TSR in Germany, 653 black-grass samples were collected between 2004 and 2012 all over the country. The samples were tested by bioassays and genetic analysis. Averaged over all tested samples, ACCase-TSR increased from 5.0% in 2004 to 54.3% in 2011. In 2012, the proportion of ACCase-TSR was lower than the previous years (38.5%). Similarly, ALS-TSR rose from 0.8% in 2007 to 13.9% in 2012. Regions with a high density of resistant black-grass samples were identified in the north and south of Germany. The data suggest a rapidly working selection of herbicide-resistant populations which may be due to current agricultural practices and the increasing use of herbicides acting on a single site..

Kaiser, Y. I. ; Menegat, A. ; Gerhards, R.. 2013. Chlorophyll fluorescence imaging: a new method for rapid detection of herbicide resistance in Alopecurus myosuroides. Weed Research (Oxford) 53 : 399 - 406.

Due to the steadily increasing number of putative herbicide-resistant weed populations, the demand for rapid in-season tests is rising. In this study, we introduce a new quantitative herbicide-resistance test system based on chlorophyll fluorescence imaging analysis of photosynthesis-related parameters. Susceptible and herbicide-resistant populations of Alopecurus myosuroides (black-grass) were cultivated in multiwell tissue culture plates containing nutrient agar and different dosages of fenoxaprop-P-ethyl and mesosulfuron+iodosulfuron. The maximum quantum efficiency of the PSII was measured 3 h after transplanting (HAT) and then for seven days every 24 h. Data of maximum quantum efficiency of the PSII were compared with standard whole-plant pot tests and molecular tests for target-site mutations. It was possible to fit dose-response curves and calculate corresponding resistance factors for ED90 for all populations tested using the chlorophyll fluorescence imaging. It was possible to distinguish between resistant and susceptible populations. The results of the chlorophyll fluorescence imaging corresponded well with the standard whole-plant pot tests in the glasshouse. However, populations with proved target-site mutations did not differ from other herbicide-resistant populations in the maximum quantum efficiency values of the PSII. We conclude that the chlorophyll fluorescence imaging provides reliable data on herbicide resistance for both modes of action tested in a shorter time and using less space, compared with standard whole-plant pot tests in the glasshouse..

Marshall, R. ; Hanley, S. J. ; Hull, R. ; Moss, S. R.. 2013. The presence of two different target-site resistance mechanisms in individual plants of Alopecurus myosuroides Huds., identified using a quick molecular test for the characterisation of six ALS and seven ACCase SNPs. Pest Management Science 69 : 727 - 737.

BACKGROUND: Target-site resistance to ALS- and ACCase-inhibiting herbicides in the grass weed Alopecurus myosuroides is associated with well-characterised allelic variants encoding ALS- and ACCase-based resistance. The potential for combined ALS and ACCase resistance presents a threat to future control, given the extent to which these herbicides are used. The authors present a primer extension method for rapid detection of known resistance-conferring substitutions. RESULTS: Individuals showing combined resistance to field-rate mesosulfuron+iodosulfuron and cycloxydim were identified in four field-collected populations, with proportions ranging from 30 to 100%. Genotyping with the SNaPshot primer extension kit showed the T197 and L574 ALS and L1781 ACCase isoforms to be associated with ALS and ACCase resistance whenever they occurred. CONCLUSION: Combined ALS and ACCase target-site resistance threatens future control of A. myosuroides. The SNaPshot extension assay provides a reliable new multiplexable method for characterising known allelic variants of the ALS and ACCase genes of A. myosuroides. The method offers significant advantages over both CAPS/dCAPS and PASA in that full genotyping can be accomplished at any nucleotide position using a single extension primer..

Cummins, I. ; Wortley, D. J. ; Sabbadin, F. ; He ZheSi ; Coxon, C. R. ; Straker, H. E. ; Sellars, J. D. ; Knight, K. ; Edwards, L. ; Hughes, D. ; Kaundun, S. S. ; Hutchings, S. J. ; Steel, P. G. ; Edwards, R.. 2013. Key role for a glutathione transferase in multiple-herbicide resistance in grass weeds. Proceedings of the National Academy of Sciences of the United States of America 110 : 5812 - 5817.

Multiple-herbicide resistance (MHR) in black-grass (Alopecurus myosuroides) and annual rye-grass (Lolium rigidum) is a global problem leading to a loss of chemical weed control in cereal crops. Although poorly understood, in common with multiple-drug resistance (MDR) in tumors, MHR is associated with an enhanced ability to detoxify xenobiotics. In humans, MDR is linked to the overexpression of a pi class glutathione transferase (GSTP1), which has both detoxification and signaling functions in promoting drug resistance. In both annual rye-grass and black-grass, MHR was also associated with the increased expression of an evolutionarily distinct plant phi (F) GSTF1 that had a restricted ability to detoxify herbicides. When the black-grass A. myosuroides (Am) AmGSTF1 was expressed in Arabidopsis thaliana, the transgenic plants acquired resistance to multiple herbicides and showed similar changes in their secondary, xenobiotic, and antioxidant metabolism to those determined in MHR weeds. Transcriptome array experiments showed that these changes in biochemistry were not due to changes in gene expression. Rather, AmGSTF1 exerted a direct regulatory control on metabolism that led to an accumulation of protective flavonoids. Further evidence for a key role for this protein in MHR was obtained by showing that the GSTP1- and MDR-inhibiting pharmacophore 4-chloro-7-nitro-benzoxadiazole was also active toward AmGSTF1 and helped restore herbicide control in MHR black-grass. These studies demonstrate a central role for specific GSTFs in MHR in weeds that has parallels with similar roles for unrelated GSTs in MDR in humans and shows their potential as targets for chemical intervention in resistant weed management..

Délye, C. ; Menchari, Y. ; Michel, S. ; Cadet, É. ; Corre, V. le. 2013. A new insight into arable weed adaptive evolution: mutations endowing herbicide resistance also affect germination dynamics and seedling emergence. Annals of Botany 111 : 681 - 691.

Background and Aims: Selective pressures exerted by agriculture on populations of arable weeds foster the evolution of adaptive traits. Germination and emergence dynamics and herbicide resistance are key adaptive traits. Herbicide resistance alleles can have pleiotropic effects on a weed's life cycle. This study investigated the pleiotropic effects of three acetyl-coenzyme A carboxylase (ACCase) alleles endowing herbicide resistance on the seed-to-plant part of the life cycle of the grass weed Alopecurus myosuroides. Methods: In each of two series of experiments, A. myosuroides populations with homogenized genetic backgrounds and segregating for Leu1781, Asn2041 or Gly2078 ACCase mutations which arose independently were used to compare germination dynamics, survival in the soil and seedling pre-emergence growth among seeds containing wild-type, heterozygous and homozygous mutant ACCase embryos. Key Results: Asn2041 ACCase caused no significant effects. Gly2078 ACCase major effects were a co-dominant acceleration in seed germination (1.25- and 1.10-fold decrease in the time to reach 50% germination (T₅₀) for homozygous and heterozygous mutant embryos, respectively). Segregation distortion against homozygous mutant embryos or a co-dominant increase in fatal germination was observed in one series of experiments. Leu1781 ACCase major effects were a co-dominant delay in seed germination (1.41- and 1.22-fold increase in T₅₀ for homozygous and heterozygous mutant embryos, respectively) associated with a substantial co-dominant decrease in fatal germination. Conclusions: Under current agricultural systems, plants carrying Leu1781 or Gly2078 ACCase have a fitness advantage conferred by herbicide resistance that is enhanced or counterbalanced, respectively, by direct pleiotropic effects on the plant phenology. Pleiotropic effects associated with mutations endowing herbicide resistance undoubtedly play a significant role in the evolutionary dynamics of herbicide resistance in weed populations. Mutant ACCase alleles should also prove useful to investigate the role played by seed storage lipids in the control of seed dormancy and germination..

1 2 3 4 5 6 ...

Page size:

select

Page: of 48

Items 1 to 5 of 237

PERMISSION MUST BE OBTAINED FIRST if you intend to base a significant portion of a scientific paper on data derived from this site. Citation:
Heap, I. The International Herbicide-Resistant Weed Database. Online. Thursday, November 21, 2024 . Available www.weedscience.org Copyright © 1993- 2024 WeedScience.org All rights reserved. Fair use of this material is encouraged. Proper citation is requested.