International Survey of Herbicide-Resistant Weeds

Countries Weeds Herbicides Mutations Graphs References Researchers
(Matricaria discoidea)

Photosystem II inhibitors (C1/5)

United Kingdom
Pineapple-weed (Matricaria discoidea) is a dicot weed in the Asteraceae family.  In United Kingdom this weed first evolved resistance to Group C1/5 herbicides in 1989 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.

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 Sep 15, 2000 )

Common NamePineapple-weed
SpeciesMatricaria discoidea
GroupPhotosystem II inhibitors (C1/5)
LocationUnited Kingdom
Contributors - (Alphabetically)Stephen Moss 
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Stephen Moss
Clay, D. V. 1989. New developments in triazine and paraquat resistance and co-resistance in weed species in England. In Brighton Crop Protection Conference - Weeds - 1989. pp 317-323.

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Confirmation Tests

Greenhouse, and Laboratory trials comparing a known susceptible Pineapple-weed biotype with this Pineapple-weed 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 Pineapple-weed 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 Pineapple-weed from United Kingdom.
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Iacr - Rothamsted
1076 Ag Sci Bldg
PO Box 6108
Harpenden, AL5 2JQ, Hertfordshire
United Kingdom
Email Stephen Moss


The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in United Kingdom have been instrumental in providing you this information. Particular thanks is given to Stephen Moss for providing detailed information.
Herbicide Resistant Pineapple-weed Globally
(Matricaria discoidea)
Herbicide Resistant Pineapple-weed Globally
(Matricaria discoidea)
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Herbicide Resistant Pineapple-weed Globally
(Matricaria discoidea)
#CountryFirstYearSituationActive IngredientsSite of Action
1 United KingdomUnited Kingdom 1989 Orchards simazine 44 Photosystem II inhibitors (C1/5)
115Matricaria discoideaPineapple-weed367
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