Bristly Foxtail (Setaria verticillata) is a monocot weed in the Poaceae family.  In Spain this weed first evolved resistance to Group C1/5 herbicides in 1992 and infests Corn (maize).   Group C1/5 herbicides are known as Photosystem II inhibitors (Inhibition of photosynthesis at photosystem II).  Research has shown that these particular biotypes are resistant to atrazine and they may be cross-resistant to other Group C1/5 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.

If we do not have a picture for this weed, or you can provide a better picture (scan, digital camera etc) please please e-mail it to us.

QUIK STATS (last updated Nov 20, 2000 )

Common NameBristly Foxtail
SpeciesSetaria verticillata
GroupPhotosystem II inhibitors (C1/5)
Situation(s)Corn (maize)
Contributors - (Alphabetically)Rafael De Prado 
Edit this Case  |  Add New Case of Resistance  |  Add Note



Rafael De Prado
Prado-R-de; Romero-E; Menendez-J; Tena-M; De-Prado-R. 1992. Mechanism of resistance to atrazine in Setaria verticillata and Setaria faberi. In IXe Colloque international sur la biologie des mauvaises herbes, 16-18 September 1992, Dijon, France. 1992, 457-463

Edit this Note  |  Add New Note

Rafael De Prado
Growth chamber experiments revealed that atrazine-resistant S.verticillata plants developed from seed collected from both atrazine-treated and non-treated maize fields in the province of Cordoba, whereas atrazine-resistant S. faberi biotypes only developed in the treated fields. The resistance to atrazine of S. verticillata from both situations was apparently due to detoxification by conjugation of the herbicide with glutathione. The atrazine-resistant S. faberi biotype could be explained by a dual mechanism: (i) a lower affinity of the herbicide for the target site in the D1 protein, and (ii) by conjugation. Although the non-treated biotype of S. faberi conjugated glutathione to atrazine, it did so less efficiently than the corresponding resistant biotype.

Edit this Note  |  Add New Note


Confirmation Tests

Greenhouse trials comparing a known susceptible Bristly Foxtail biotype with this Bristly Foxtail 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 C1/5 resistant Bristly Foxtail 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 C1/5 resistant Bristly Foxtail from Spain indicate that resistance is due to conjugation.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
Relative Fitness

Triazine resistant weeds often exhibit a lower relative fitness when compared to susceptible biotypes.  The most common mutation conferring triazine resistance (Ser 264 to Gly mutation of the psbA gene) also causes a reduction in CO2 fixation, quantum yield, and seed and biomass production.  There is no record in this database referring specifically to fitness studies on Group C1/5 resistant Bristly Foxtail from Spain.
Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  


Universidad De Cordoba
Qvimica Agricola Y Edafologa
E T S Ingenieros Agronomos
PO Box 119
Cordoba, E-14080, Andalusia
Email Rafael De Prado


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Spain have been instrumental in providing you this information. Particular thanks is given to Rafael De Prado for providing detailed information.
Herbicide Resistant Bristly Foxtail Globally
(Setaria verticillata)
Herbicide Resistant Bristly Foxtail Globally
(Setaria verticillata)
Drag a column header and drop it here to group by that column
Herbicide Resistant Bristly Foxtail Globally
(Setaria verticillata)
#CountryFirstYearSituationActive IngredientsSite of Action
1 SpainSpain 1992 Corn (maize) atrazine 38 Photosystem II inhibitors (C1/5)
152Setaria verticillataBristly Foxtail436
Literature about Similar Cases

Page size:
Page: of 2
Items 1 to 5 of 9

Page size:
Page: of 2
Items 1 to 5 of 9

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.  Saturday, August 8, 2020 .  Available Copyright © 1993- 2020 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.