International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Sagittaria montevidensis)

ALS inhibitors (B/2)

China, Jilin
California Arrowhead (Sagittaria montevidensis) is a monocot weed in the Alismataceae family.  In China this weed first evolved resistance to Group B/2 herbicides in 2003 and infests Rice.   Group B/2 herbicides are known as ALS inhibitors (Inhibition of Acetolactate Synthase ).  Research has shown that these particular biotypes are resistant to bensulfuron-methyl, and pyrazosulfuron-ethyl and they may be cross-resistant to other Group B/2 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 Jul 10, 2007 )

Common NameCalifornia Arrowhead
SpeciesSagittaria montevidensis
GroupALS inhibitors (B/2)
Herbicidesbensulfuron-methyl, and pyrazosulfuron-ethyl
LocationChina, Jilin
Contributors - (Alphabetically)José Noldin 
Edit this Case  |  Add New Case of Resistance  |  Add Note


Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible California Arrowhead biotype with this California Arrowhead 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 B/2 resistant California Arrowhead indicate that the inheritance is determined by a one gene, semi dominant, nuclear trait.  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 B/2 resistant California Arrowhead from China indicate that resistance is due to an altered target site, and sequestration.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
Relative Fitness

Researchers have indicated that Group B/2 resistant California Arrowhead is ecologically less fit than normal susceptible California Arrowhead.  There may be a note below or an article discussing the fitness of this biotype in the Fact Sheets and Other Literature
Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  Help


Weed Scientist
Epagri - Agri. And Extn Inst. For Santa Catarina State
Itajai Experiment Station
Dept of Agronomy Horticulture
PO Box 830915, 362 Plant Science
Itajaí, 88301-970, Santa Catarina
Email José Noldin


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in China have been instrumental in providing you this information. Particular thanks is given to José Noldin for providing detailed information.
Herbicide Resistant California Arrowhead Globally
(Sagittaria montevidensis)
Herbicide Resistant California Arrowhead Globally
(Sagittaria montevidensis)
Drag a column header and drop it here to group by that column
Herbicide Resistant California Arrowhead Globally
(Sagittaria montevidensis)
#CountryFirstYearSituationActive IngredientsSite of Action
1 Australia (New South Wales ) AustraliaNew South Wales 1994 Rice bensulfuron-methyl 1 ALS inhibitors (B/2)
146Sagittaria montevidensisCalifornia Arrowhead7
2 BrazilBrazil 1999 Rice bispyribac-sodium, cyclosulfamuron, ethoxysulfuron, metsulfuron-methyl, and pyrazosulfuron-ethyl 5 ALS inhibitors (B/2)
146Sagittaria montevidensisCalifornia Arrowhead1179
3 BrazilBrazil 2009 Rice bentazon, bispyribac-sodium, ethoxysulfuron, imazethapyr, metsulfuron-methyl, penoxsulam, and pyrazosulfuron-ethyl 5 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
PSII inhibitors - Histidine 215 Binders (C3/6)
146Sagittaria montevidensisCalifornia Arrowhead5588
4 ChinaChina 2003 Rice bensulfuron-methyl, and pyrazosulfuron-ethyl 9 ALS inhibitors (B/2)
146Sagittaria montevidensisCalifornia Arrowhead5303
5 United States (California) United StatesCalifornia1993 Rice bensulfuron-methyl 45 ALS inhibitors (B/2)
146Sagittaria montevidensisCalifornia Arrowhead390
Literature about Similar Cases

Page size:
Page: of 2
Items 1 to 5 of 7

Page size:
Page: of 2
Items 1 to 5 of 7
PERMISSION MUST BE OBTAINED FIRST if you intend to base a significant portion of a scientific paper on data derived from this site.
Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Monday, April 19, 2021 .  Available
Copyright © 1993- 2021 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.