International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Sagittaria montevidensis)

ALS inhibitors (B/2)

Australia, New South Wales
California Arrowhead (Sagittaria montevidensis) is a monocot weed in the Alismataceae family.  In New South Wales this weed first evolved resistance to Group B/2 herbicides in 1994 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 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 Jun 06, 2004 )

Common NameCalifornia Arrowhead
SpeciesSagittaria montevidensis
GroupALS inhibitors (B/2)
LocationAustralia, New South Wales
Contributors - (Alphabetically)Jim Pratley 
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Jim Pratley
Irrigation areas of southern NSW.

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Jim Pratley
Little scope for chemical control of Arrowhead after bensulfuron is gone.

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Confirmation Tests

Greenhouse 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 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 B/2 resistant California Arrowhead from New South Wales please update the database.
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Dean, Faculty Of Science & Agriculture
Charles Sturt University
School Of Agriculture
Dept of Crop& Soil Sciences
PO Box 646420,
Wagga Wagga, 2678, New South Wales
Email Jim Pratley


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in New South Wales have been instrumental in providing you this information. Particular thanks is given to Jim Pratley 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

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