(Monochoria vaginalis)

ALS inhibitors (B/2)

South Korea
Arrowleafed Monochoria (Monochoria vaginalis) is a monocot weed in the Pontederiaceae family.  In South Korea this weed first evolved resistance to Group B/2 herbicides in 1999 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 Mar 05, 2001 )

Common NameArrowleafed Monochoria
SpeciesMonochoria vaginalis
GroupALS inhibitors (B/2)
LocationSouth Korea
Contributors - (Alphabetically)Tae Seon Park 
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Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Arrowleafed Monochoria biotype with this Arrowleafed Monochoria 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 Arrowleafed Monochoria 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 Arrowleafed Monochoria from South Korea please update the database.
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Physiology Of Herbicide Action
National Institute Of Agricultural Science And Technology
Department Of Crop Protection
Dept of Plant Sciences
51 Campus Dr.,
Suweon, 441-707
South Korea
Email Tae Seon Park


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in South Korea have been instrumental in providing you this information. Particular thanks is given to Tae Seon Park for providing detailed information.
Herbicide Resistant Arrowleafed Monochoria Globally
(Monochoria vaginalis)
Herbicide Resistant Arrowleafed Monochoria Globally
(Monochoria vaginalis)
Drag a column header and drop it here to group by that column
Herbicide Resistant Arrowleafed Monochoria Globally
(Monochoria vaginalis)
#CountryFirstYearSituationActive IngredientsSite of Action
1 ChinaChina 2010 Rice bensulfuron-methyl 9 ALS inhibitors (B/2)
202Monochoria vaginalisArrowleafed Monochoria5655
2 JapanJapan 1998 Rice bensulfuron-methyl 25 ALS inhibitors (B/2)
202Monochoria vaginalisArrowleafed Monochoria7764
3 South KoreaSouth Korea 1999 Rice bensulfuron-methyl 27 ALS inhibitors (B/2)
202Monochoria vaginalisArrowleafed Monochoria151
Literature about Similar Cases

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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, April 17, 2021 .  Available Copyright © 1993- 2021 All rights reserved. Fair use of this material is encouraged. Proper citation is requested.