International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Landoltia punctata)

PSI Electron Diverter (D/22)

United States, Florida
Dotted Duckweed (Landoltia punctata) is a dicot weed in the Lemnaceae family.  In Florida this weed first evolved resistance to Group D/22 herbicides in 2001 and infests Aquatic.   Group D/22 herbicides are known as PSI Electron Diverter (Photosystem-I-electron diversion).  Research has shown that these particular biotypes are resistant to diquat, and paraquat and they may be cross-resistant to other Group D/22 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 May 24, 2005 )

Common NameDotted Duckweed
SpeciesLandoltia punctata
GroupPSI Electron Diverter (D/22)
Herbicidesdiquat, and paraquat
LocationUnited States, Florida
Contributors - (Alphabetically)Tyler Koschnick 
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Confirmation Tests

Laboratory trials comparing a known susceptible Dotted Duckweed biotype with this Dotted Duckweed 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 D/22 resistant Dotted Duckweed 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 D/22 resistant Dotted Duckweed from Florida please update the database.
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Visiting Assistant Professor
University Of Florida
915 W State St
Gainesville, 32653, Florida
United States
Email Tyler Koschnick


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Florida have been instrumental in providing you this information. Particular thanks is given to Tyler Koschnick for providing detailed information.
Herbicide Resistant Dotted Duckweed Globally
(Landoltia punctata)
Herbicide Resistant Dotted Duckweed Globally
(Landoltia punctata)
Drag a column header and drop it here to group by that column
Herbicide Resistant Dotted Duckweed Globally
(Landoltia punctata)
#CountryFirstYearSituationActive IngredientsSite of Action
1 United States (Florida) United StatesFlorida2001 Aquatic diquat, and paraquat 45 PSI Electron Diverter (D/22)
232Landoltia punctataDotted Duckweed5247
Literature about Similar Cases

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