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1 July 2005 A Common Ragweed (Ambrosia artemisiifolia) Biotype in Southwestern Québec Resistant to Linuron
SOPHIE SAINT-LOUIS, ANTONIO DiTOMMASO, ALAN K. WATSON
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Abstract

The degree of resistance to linuron of a common ragweed biotype was investigated. Suspected linuron-resistant plants collected from a carrot field near Sherrington, Québec, were subjected to increasing rates of linuron under glasshouse conditions. Resistance to linuron of the common ragweed biotype was suspected because 33% of plants survived to reproduction after they were sprayed at a rate of 4.5 kg ai/ha, two times the dose rate recommended for linuron in carrots, and also because 3% of plants survived to reproduction after they were sprayed at a rate of 22.5 kg ai/ ha, 10 times the recommended dose. Susceptible plants collected from a field with no prior history of linuron use were all killed when sprayed at the lowest dose rate recommended, 1.125 kg ai/ha. The herbicide-resistance ratio was 29.0 for linuron, and for cross-resistance to atrazine, the ratio was 1.3, indicating that these plants exhibit greater resistance to linuron than to atrazine.

Nomenclature: Linuron; common ragweed, Ambrosia artemisiifolia L. #3 AMBEL; carrot, Daucus carota L.

Additional index words: Urea herbicides, cross-resistance, atrazine.

SOPHIE SAINT-LOUIS, ANTONIO DiTOMMASO, and ALAN K. WATSON "A Common Ragweed (Ambrosia artemisiifolia) Biotype in Southwestern Québec Resistant to Linuron," Weed Technology 19(3), 737-743, (1 July 2005). https://doi.org/10.1614/WT-04-276.1
Published: 1 July 2005
JOURNAL ARTICLE
7 PAGES


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