International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Abutilon theophrasti)

Photosystem II inhibitors (C1/5)

United States, Michigan
Velvetleaf (Abutilon theophrasti) is a dicot weed in the Malvaceae family.  In Michigan this weed first evolved resistance to Group C1/5 herbicides in 2004 and infests Corn (maize), Nurseries, and Soybean.   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.

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QUIK STATS (last updated Mar 05, 2007 )

Common NameVelvetleaf
SpeciesAbutilon theophrasti
GroupPhotosystem II inhibitors (C1/5)
LocationUnited States, Michigan
Situation(s)Corn (maize), Nurseries, and Soybean
Contributors - (Alphabetically)Steven Gower 
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Confirmation Tests

Field, and Greenhouse trials comparing a known susceptible Velvetleaf biotype with this Velvetleaf 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 Velvetleaf 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

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 Velvetleaf from Michigan.
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Former Weed Science Diagnostician (Now with Monsanto)
Michigan State University
Diagnostic Services
578 Wilson Rd.
East Lansing, 48824, Michigan
United States
Email Steven Gower


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Michigan have been instrumental in providing you this information. Particular thanks is given to Steven Gower for providing detailed information.
Herbicide Resistant Velvetleaf Globally
(Abutilon theophrasti)
Herbicide Resistant Velvetleaf Globally
(Abutilon theophrasti)
Drag a column header and drop it here to group by that column
Herbicide Resistant Velvetleaf Globally
(Abutilon theophrasti)
#CountryFirstYearSituationActive IngredientsSite of Action
1 United States (Maryland) United StatesMaryland1984 Corn (maize), and Cropland atrazine 45 Photosystem II inhibitors (C1/5)
1Abutilon theophrastiVelvetleaf425
2 United States (Wisconsin) United StatesWisconsin1990 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
1Abutilon theophrastiVelvetleaf410
3 United States (Minnesota) United StatesMinnesota1991 Corn (maize) atrazine 45 Photosystem II inhibitors (C1/5)
1Abutilon theophrastiVelvetleaf244
4 United States (Michigan) United StatesMichigan2004 Corn (maize), Nurseries, and Soybean atrazine 45 Photosystem II inhibitors (C1/5)
1Abutilon theophrastiVelvetleaf5289
Literature about Similar Cases

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Cite this site as: Heap, I.  The International Survey of Herbicide Resistant Weeds.  Online.  Internet.  Tuesday, November 24, 2020 .  Available
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