Multiple resistant Apera spica-venti from Denmark

International Survey of Herbicide-Resistant Weeds

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Saturday, July 12, 2025

MULTIPLE RESISTANT SILKY WINDGRASS
(Apera spica-venti)

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)

Denmark

INTRODUCTION		SILKY WINDGRASS
Silky Windgrass (Apera spica-venti) is a monocot weed in the Poaceae family. In Denmark this weed first evolved multiple resistance (to 2 herbicide sites of action) in 2016 and infests Wheat. Multiple resistance has evolved to herbicides in the Groups 1 (Legacy A), and Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B). These particular biotypes are known to have resistance to fenoxaprop-ethyl, florasulam, iodosulfuron-methyl-Na, mesosulfuron-methyl, and pinoxaden and they may be cross-resistant to other herbicides in the Groups 1 (Legacy A), and Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B). 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 07, 2017 )
Common Name	Silky Windgrass
Species	Apera spica-venti
Group	Inhibition of Acetyl CoA Carboxylase HRAC Group 1 (Legacy A) Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	fenoxaprop-ethyl, florasulam, iodosulfuron-methyl-Na, mesosulfuron-methyl, and pinoxaden
Location	Denmark
Year	2016
Situation(s)	Wheat
Contributors - (Alphabetically)	Solvejg Mathiassen
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NOTES ABOUT THIS BIOTYPE

GENERAL

Solvejg Mathiassen

April 2017 Update

Apera spica-venti

7 verified cases – all from fields in which farmers or advisors suspected resistance. The resistance factors indicate the mechanism to be enhanced metabolism. Genotyping: None of the seven ALS mutations were found in 16 populations tested. Mutations in ACCase genes were found at two positions Ile1781 and Ile 2041. The overall frequency of ALS and ACCase NTSR activity correlated well with the resistant phenotypes. Genotyping performed by Bayer CropScience. References: Babineau M.: Microevolution of ALS inhibitor herbicide resistance in loose silky bentgrass (Apera spica-venti). PhD dissertation, Department of Agroecology, Aarhus University, January 2017. Babineau M., Mahmood K., Mathiassen S.K., Kudsk P., Kristensen M. (2017): De novo transcriptome assembly analysis of weed Apera spica-venti from seven tissues and growth stages. BMC Genomics, vol. 18, 128, 06.02.2017 Babineau M., Solvejg K. Mathiassen, Michael Kristensen, Niels Holst, Roland Beffa and Per Kudsk (2017): Spatial Distribution of ALS Resistance Mechanisms in Neighboring Populations of Apera spica-venti. Accepted for publication in Weed Science, March 2017

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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Silky Windgrass biotype with this Silky Windgrass 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 1, 2 resistant Silky Windgrass 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 multiple resistant Silky Windgrass from Denmark indicate that resistance is due to an altered target site, and 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 multiple resistant Silky Windgrass from Denmark please update the database.

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CONTRIBUTING WEED SCIENTISTS

SOLVEJG MATHIASSEN

Senior Scientist Aarhus University, Science and Technology Dept. of Agroecology P.o. Box 30 Slagelse, 4200, Slagelse Municipality Denmark Email Solvejg Mathiassen

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

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Herbicide Resistant Silky Windgrass Globally
(Apera spica-venti)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Austria

2009

Cereals

iodosulfuron-methyl-Na, and isoproturon

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

Belgium

2019

Wheat

foramsulfuron, iodosulfuron-methyl-Na, and mesosulfuron-methyl

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

Czech Republic

2005

Cereals, and Winter wheat

chlorsulfuron, iodosulfuron-methyl-Na, isoproturon, mesosulfuron-methyl, pyroxsulam, and sulfosulfuron

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

Denmark

2011

Winter wheat

iodosulfuron-methyl-Na, and sulfosulfuron

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

Denmark

2016

Wheat

fenoxaprop-ethyl, florasulam, iodosulfuron-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)

France

2006

Wheat

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

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

Germany

1997

Cereals, and Winter wheat

isoproturon

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

Germany

2005

Wheat

chlorsulfuron, florasulam, flupyrsulfuron-methyl-Na, iodosulfuron-methyl-Na, mesosulfuron-methyl, pyroxsulam, sulfometuron-methyl, and sulfosulfuron

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

Germany

2009

Spring Barley, and Winter wheat

fenoxaprop-ethyl, iodosulfuron-methyl-Na, isoproturon, mesosulfuron-methyl, pinoxaden, pyroxsulam, and sulfosulfuron

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)

Latvia

2015

Wheat, and Winter wheat

iodosulfuron-methyl-Na

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

Lithuania

2013

Winter wheat

iodosulfuron-methyl-Na

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

Poland

2005

Winter wheat

chlorsulfuron, iodosulfuron-methyl-Na, procarbazone-Na, and sulfosulfuron

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

Poland

2010

Winter wheat

fenoxaprop-ethyl, and pinoxaden

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

Poland

2011

Winter wheat

chlorsulfuron, fenoxaprop-ethyl, pinoxaden, sulfometuron-methyl, and sulfosulfuron

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)

Poland

2012

Winter wheat

isoproturon

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

Sweden

2006

Winter wheat

isoproturon

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

Sweden

2010

Winter wheat

iodosulfuron-methyl-Na, pyroxsulam, and sulfosulfuron

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

Switzerland

1994

Wheat

isoproturon

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

Literature about Similar Cases

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Katerina Hamouzová, Pavlíina Košnarová, Jaroslav Salava, Josef Soukup and Pavel Hamouza. 2013. Mechanisms of resistance to acetolactate synthase-inhibiting herbicides in populations ofApera spica-ventifrom the Czech Republic. Pest Management Science : .

BACKGROUND: This study investigates the mechanisms of resistance to acetolactate synthase-inhibiting herbicides in populations of Apera spica-venti (L.) P.B. from the Czech Republic.

RESULTS: The proportion of resistance due to mutant acetolactate synthase (ALS) alleles was estimated by genotyping individuals from each of three populations for the eight ALS mutations known to confer resistance. Four resistance-conferring ALS mutations were identified: Pro-197-Ala, Pro-197-Thr, Trp-574-Leu and previously unreported Trp-574-Met substitution. Two populations (R1, R3) have amino acid substitution at positions Pro-197 and Trp-574. Individuals from the R3 population had two different resistance alleles. In the R2 population, only the resistant Trp-574-Met substitution was detected. Ten other single point mutations were identified, but these were not related to resistance.

The cytochrome malathion decreased chlorsulfuron resistance in the resistant populations that were examined. Although malathion increased mortality, the GR50 values were too high to conclude that non-target-based mechanism was the main one for the resistance in Apera spica-venti populations tested in this study.
CONCLUSIONS: Individuals of Apera spica-venti populations tested in this study possess the target-site ALS resistance mutation and an additional so far unknown resistance mechanism(s)..

Wolber, D. ; Warnecke-Busch, G. ; Wagner, J.. 2012. Herbizidresistence at Alopecurus myosuroides und Apera spica-venti in Lower Saxony. Julius-Kühn-Archiv : 443 - 445.

Wagner, J. ; Wolber, D.. 2012. Occurence of herbicide resistance to ALS-inhibitors and of resistance alleles identified by pyrosequencing in Alopecurus myosuroides Huds. (blackgrass) und Apera spica-venti (L.) Beauv. (silky bent-grass) in agricultural areas from Lower Saxony. Julius-Kühn-Archiv : .

Rummland, J. ; Kerlen, D. ; Nordmeyer, H. ; Richter, O.. 2012. Modelling the development of herbicide resistance. Julius-Kühn-Archiv 1 : 149 - 154.

A population dynamic and genetic model was used to simulate the genetic evolution in an Apera spica-venti (L.) P. Beauv. population. The basis of the model is a life cycle of an annual weed population which is divided into five development stages. These are the seed bank, the seedlings, young plants, the seed producing plants and the produced seeds. The stages are linked through transition probabilities. The interaction between resistant and susceptible genotypes is mediated by a genetic submodel. The model supports the development of management strategies to prevent, reduce or at least retard the development of resistance. Through an embedment into a cellular automaton the dispersal of genetic information is simulated at field scale. Three simulations with different herbicide treatments are compared regarding the resistance evolution..

Petersen, J. ; Naruhn, G. ; Raffel, H.. 2012. Non target-site resistance inherent in Alopecurus myosuroides and Apera spica-venti - resistance pattern and factors. Julius-Kühn-Archiv 1 : 43 - 50.

Alopecurus myosuroides and Apera spica-venti are the most important grass weeds in German cereal cropping systems. Both species show increasing resistance problems with herbicide resistant biotypes in many regions. In many cases, non target-site resistance (TSR) mechanism can be detected. In these biotypes resistance is assumingly based on non target-site-mechanisms (NTSR) and an enhanced metabolism might be responsible in the first place. Resistance in A. spica-venti biotypes can also be found against pre-emergence herbicides like diflufenican and pendimethalin. However, untill now no resistance in A. spica-venti against the active ingredients flurtamone, flufenacet and prosulfocarb could be detected. A. myosuroides biotypes also frequently show NTSR mechanisms. Resistance patterns are variable and predictions about the efficacy of one herbicide cannot be made based on the knowledge of the effects of another ingredient even within the same mode of action group. The resistance patterns of different A. myosuroides biotypes and crosses indicate a complex, polygenetic control of NTSR mechanisms..

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