(Apera spica-venti)

PSII inhibitor (Ureas and amides) (C2/7)

Poland, North-East Region
Silky Windgrass (Apera spica-venti) is a monocot weed in the Poaceae family.  In Poland this weed first evolved resistance to Group C2/7 herbicides in 2012 and infests Winter wheat.   Group C2/7 herbicides are known as PSII inhibitor (Ureas and amides) (Inhibition of photosynthesis at photosystem II).  Research has shown that these particular biotypes are resistant to isoproturon and they may be cross-resistant to other Group C2/7 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.

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QUIK STATS (last updated Dec 08, 2013 )

Common NameSilky Windgrass
SpeciesApera spica-venti
GroupPSII inhibitor (Ureas and amides) (C2/7)
LocationPoland, North-East Region
Situation(s)Winter wheat
Contributors - (Alphabetically)Kazimierz Adamczewski 
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Kazimierz Adamczewski

General information for Wind bent grass (Apera spica-venti)

The seeds of wind bent grass (Apera spica-venti) become from difference sites from North-East part of Poland. And the seeds were collected from field were inhibitors of photosynthesis at photosystem II for many years was used for control this grass weed and farmer got poor control. During years 2010-20012  samples from 16 fields were collected.   Four replication greenhouse trials comparing with known susceptible Wind Bentgrass with collected samples was done. For testing the samples two types of experiments were used.

At first experiment in one dose of 2 herbicides, chlorotoluron and isoproturon  were applied. Two and 4 weeks after application visual assessment were done. With 4 selected  populations (biotypes)  second type of experiments were done.  At this trials  isoproturon  in 7 deference dose were used, (low and high dose). And 4 weeks after treatment, the plants were cut at the soil surface and their fresh weight was determined. The obtained results were expressed to percent of control to untreated. The susceptible biotype (S) as standard was used. The results was used for calculation to define of effecting dose for calculation the ratio and  ED50 for resistance and susceptible population, and for resistance index calculation.  Two biotypes from 4 tested were resistance to isoproturon. For each treatment four pot were used as four replication. Statistical analysis of date from greenhouse experiments was performed.  

Confirmation Test. Greenhouse and field  trials comparing a known susceptible wind Bent grass biotype with these wind Bent grass biotypes have been used to confirm resistance.

Mechanism of Resistance  is unknown.

Relative Fitness. There is no done.

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Confirmation Tests

Greenhouse 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.

Genetic studies on Group C2/7 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

The mechanism of resistance for this biotype is either unknown or has not been entered in the database.  If you know anything about the mechanism of resistance for this biotype then please update the database.
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 C2/7 resistant Silky Windgrass from Poland please update the database.
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Institute Of Plant Protection - National Research Institute
Depart. Of Weed Science
Str. Wladyslawa Wegorka 20
Poznań, 60-318, Poznań
Email Kazimierz Adamczewski


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Poland have been instrumental in providing you this information. Particular thanks is given to Kazimierz Adamczewski for providing detailed information.
Herbicide Resistant Silky Windgrass Globally
(Apera spica-venti)
Herbicide Resistant Silky Windgrass Globally
(Apera spica-venti)
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Herbicide Resistant Silky Windgrass Globally
(Apera spica-venti)
#CountryFirstYearSituationActive IngredientsSite of Action
1 AustriaAustria 2009 Cereals iodosulfuron-methyl-sodium, and isoproturon 2 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
PSII inhibitor (Ureas and amides) (C2/7)
20Apera spica-ventiSilky Windgrass6746
2 BelgiumBelgium 2019 Wheat foramsulfuron, iodosulfuron-methyl-sodium, and mesosulfuron-methyl 3 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass18199
3 Czech RepublicCzech Republic 2005 Cereals, and Winter wheat chlorsulfuron, iodosulfuron-methyl-sodium, isoproturon, mesosulfuron-methyl, pyroxsulam, and sulfosulfuron 12 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
PSII inhibitor (Ureas and amides) (C2/7)
20Apera spica-ventiSilky Windgrass5266
4 DenmarkDenmark 2011 Winter wheat iodosulfuron-methyl-sodium, and sulfosulfuron 13 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass5674
5 DenmarkDenmark 2016 Wheat fenoxaprop-P-ethyl, florasulam, iodosulfuron-methyl-sodium, mesosulfuron-methyl, and pinoxaden 13 Multiple Resistance: 2 Sites of Action
ACCase inhibitors (A/1)
ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass15078
6 FranceFrance 2006 Wheat iodosulfuron-methyl-sodium, mesosulfuron-methyl, and pyroxsulam 17 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass9936
7 GermanyGermany 1997 Cereals, and Winter wheat isoproturon 18 PSII inhibitor (Ureas and amides) (C2/7)
20Apera spica-ventiSilky Windgrass5026
8 GermanyGermany 2005 Wheat chlorsulfuron, florasulam, flupyrsulfuron-methyl-sodium, iodosulfuron-methyl-sodium, mesosulfuron-methyl, pyroxsulam, sulfometuron-methyl, and sulfosulfuron 18 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass5526
9 GermanyGermany 2009 Spring Barley, and Winter wheat fenoxaprop-P-ethyl, iodosulfuron-methyl-sodium, isoproturon, mesosulfuron-methyl, pinoxaden, pyroxsulam, and sulfosulfuron 18 Multiple Resistance: 3 Sites of Action
ACCase inhibitors (A/1)
ALS inhibitors (B/2)
PSII inhibitor (Ureas and amides) (C2/7)
20Apera spica-ventiSilky Windgrass5410
10 LatviaLatvia 2015 Wheat, and Winter wheat iodosulfuron-methyl-sodium 174 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass15067
11 LithuaniaLithuania 2013 Winter wheat iodosulfuron-methyl-sodium 185 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass7821
12 PolandPoland 2005 Winter wheat chlorsulfuron, iodosulfuron-methyl-sodium, procarbazone-sodium, and sulfosulfuron 33 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass5395
13 PolandPoland 2010 Winter wheat fenoxaprop-P-ethyl, and pinoxaden 33 ACCase inhibitors (A/1)
20Apera spica-ventiSilky Windgrass5619
14 PolandPoland 2011 Winter wheat chlorsulfuron, fenoxaprop-P-ethyl, pinoxaden, sulfometuron-methyl, and sulfosulfuron 33 Multiple Resistance: 2 Sites of Action
ACCase inhibitors (A/1)
ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass6758
15 PolandPoland 2012 Winter wheat isoproturon 33 PSII inhibitor (Ureas and amides) (C2/7)
20Apera spica-ventiSilky Windgrass6759
16 SwedenSweden 2006 Winter wheat isoproturon 40 PSII inhibitor (Ureas and amides) (C2/7)
20Apera spica-ventiSilky Windgrass10996
17 SwedenSweden 2010 Winter wheat iodosulfuron-methyl-sodium, pyroxsulam, and sulfosulfuron 40 ALS inhibitors (B/2)
20Apera spica-ventiSilky Windgrass10994
18 SwitzerlandSwitzerland 1994 Wheat isoproturon 41 PSII inhibitor (Ureas and amides) (C2/7)
20Apera spica-ventiSilky Windgrass208
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