International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
GROUP C1/5 RESISTANT PROSTRATE PIGWEED
(Amaranthus blitoides)


Photosystem II inhibitors (C1/5)

Spain
INTRODUCTION PROSTRATE PIGWEED
Prostrate Pigweed (Amaranthus blitoides) is a dicot weed in the Amaranthaceae family.  In Spain this weed first evolved resistance to Group C1/5 herbicides in 1986 and infests Orchards.   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 simazine 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 Nov 18, 2000 )

Common NameProstrate Pigweed
SpeciesAmaranthus blitoides
GroupPhotosystem II inhibitors (C1/5)
Herbicidessimazine
LocationSpain
Year1986
Situation(s)Orchards
Contributors - (Alphabetically)Rafael De Prado 
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NOTES ABOUT THIS BIOTYPE

GENERAL

Rafael De Prado
Target site mechanism of resistance.

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ACADEMIC ASPECTS

Confirmation Tests

Field, Greenhouse, and Laboratory trials comparing a known susceptible Prostrate Pigweed biotype with this Prostrate Pigweed biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.
 
Genetics

Genetic studies on Group C1/5 resistant Prostrate Pigweed 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

Studies on the mechanism of resistance of Group C1/5 resistant Prostrate Pigweed from Spain indicate that resistance is due to an altered target site.  There may be a note below or an article discussing the mechanism of resistance in the Fact Sheets and Other Literature
 
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 Prostrate Pigweed from Spain.
 
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CONTRIBUTING WEED SCIENTISTS

RAFAEL DE PRADO
Universidad De Cordoba
Qvimica Agricola Y Edafologa
E T S Ingenieros Agronomos
PO Box 119
Cordoba, E-14080, Andalusia
Spain
Email Rafael De Prado

ACKNOWLEDGEMENTS

The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Spain have been instrumental in providing you this information. Particular thanks is given to Rafael De Prado for providing detailed information.
Herbicide Resistant Prostrate Pigweed Globally
(Amaranthus blitoides)
Herbicide Resistant Prostrate Pigweed Globally
(Amaranthus blitoides)
Drag a column header and drop it here to group by that column
Herbicide Resistant Prostrate Pigweed Globally
(Amaranthus blitoides)
#CountryFirstYearSituationActive IngredientsSite of Action
1 IsraelIsrael 1983 Cropland, and Roadsides atrazine, and simazine 23 Photosystem II inhibitors (C1/5)
9Amaranthus blitoidesProstrate Pigweed100
2 IsraelIsrael 1991 Forests, and Roadsides atrazine, chlorsulfuron, and simazine 23 Multiple Resistance: 2 Sites of Action
ALS inhibitors (B/2)
Photosystem II inhibitors (C1/5)
9Amaranthus blitoidesProstrate Pigweed108
3 SpainSpain 1986 Orchards simazine 38 Photosystem II inhibitors (C1/5)
9Amaranthus blitoidesProstrate Pigweed183
4 United States (Michigan) United StatesMichigan2012 Mint terbacil 45 Photosystem II inhibitors (C1/5)
9Amaranthus blitoidesProstrate Pigweed5736
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