HRAC GROUP 22 (LEGACY D) RESISTANT VIRGINIA PEPPERWEED
(Lepidium virginicum)

PS I Electron Diversion HRAC Group 22 (Legacy D)

Canada, Ontario

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INTRODUCTION VIRGINIA PEPPERWEED Virginia Pepperweed (Lepidium virginicum) is a dicot weed in the Brassicaceae family.  In Ontario this weed first evolved resistance to Group 22 (Legacy D) herbicides in 1993 and infests Peaches.   Group 22 (Legacy D) herbicides are known as PS I Electron Diversion (PSI Electron Diversion ).  Research has shown that these particular biotypes are resistant to paraquat and they may be cross-resistant to other Group 22 (Legacy D) 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.

QUIK STATS (last updated Jun 06, 2000 ) Common Name Virginia Pepperweed Species Lepidium virginicum Group PS I Electron Diversion HRAC Group 22 (Legacy D) Herbicides paraquat Location Canada, Ontario Year 1993 Situation(s) Peaches Contributors - (Alphabetically) Susan Weaver  Edit this Case  |  Add New Case of Resistance  |  Add Note

NOTES ABOUT THIS BIOTYPE GENERAL Hugh Beckie A. Smisek, C. Doucet, M. Jones, and S. Weaver. 1998. Paraquat resistance in horseweed (Conyza canadensis) and Virginia pepperweed (Lepidium virginicum) from Essex County, Ontario. Weed Sci. 46:200-204. Edit this Note  |  Add New Note

ACADEMIC ASPECTS Confirmation Tests Greenhouse, and Laboratory trials comparing a known susceptible Virginia Pepperweed biotype with this Virginia Pepperweed 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 HRAC Group 22 resistant Virginia Pepperweed 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 22 (Legacy D) resistant Virginia Pepperweed from Ontario please update the database.   Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  Help

CONTRIBUTING WEED SCIENTISTS SUSAN WEAVER Agriculture And Agri-Food Canada Greenhouse And Processing Crops Research Centre Dept Plant Science MS4 Robbins Hall, Harrow, NOR 1G0, Ontario Canada Email Susan Weaver

ACKNOWLEDGEMENTS The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Ontario have been instrumental in providing you this information. Particular thanks is given to Susan Weaver for providing detailed information.

Herbicide Resistant Virginia Pepperweed Globally (Lepidium virginicum) Herbicide Resistant Virginia Pepperweed Globally (Lepidium virginicum) Drag a column header and drop it here to group by that column Herbicide Resistant Virginia Pepperweed Globally (Lepidium virginicum) # Country Country StateName FirstYear Situation Active Ingredients CountryID Site of Action WeedID Species CommonName ResistID 1 Canada (Ontario) Canada Ontario 1993 Peaches paraquat 7 PS I Electron Diversion ( HRAC Group 22 (Legacy D) 103 Lepidium virginicum Virginia Pepperweed 49

Literature about Similar Cases

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Ferreira, L. R. ; Durigan, J. C. ; Churata-Masca, M. G. C. ; Ferreira, F. A. ; Silva, A. A.. 2000. Selectivity and efficacy of the sequential application of oxyfluorfen and ioxynyl-octanoate in direct sowing of onion. Planta Daninha 18 : 39 - 50.

Experiments were conducted from 8 March to 7 October 1996 in Minas Gerais, Brazil to evaluate the efficacy of oxyfluorfen and ioxynil-octanoate [ioxynil] in controlling the weeds infesting direct-sown onion cv. Granex 33. Oxyfluorfen (at 0.048, 0.096, 0.144, 0.240, and 0.192 kg/ha) and ioxynil-octanoate (at 0.125, 0.250, 0.375, 0.625, 0.25 and 0.50 kg/ha) were applied either as single or split applications. Ioxynil-octanoate, applied at rates higher that 0.125 kg/ha at 19 days after sowing (DAS), was less selective to Granex 33 than oxyfluorfen. Split application of oxyfluorfen and ioxynil-octanoate increased the herbicide tolerance of onion plants. Oxyfluorfen at the evaluated rates controlled Galinsoga parviflora and Amaranthus hybridus, but not Lepidium virginicum and Coronopus didymus. Ioxynil-octanoate applied at 0.125 kg/ha at 19 DAS plus two applications of 0.25 kg/ha at 34 and 65 DAS controlled the existing weeds and resulted in bulb production al levels similar to the control. None of the herbicides affected postharvest bulb conservation up to 120 days of storage..

Smisek, A. ; Doucet, C. ; Jones, M. ; Weaver, S.. 1998. Paraquat resistance in horseweed (Conyza canadensis) and Virginia pepperweed (Lepidium virginicum) from Essex County, Ontario. Weed Science 46 : 200 - 204.

Populations of horseweed and Virginia pepperweed resistant to paraquat were found in 1994 in several fruit orchards in Essex County, Ontario, Canada, where paraquat had been applied 4-5 times per year for at least 10 years. Dose-response experiments were conducted in the greenhouse for each species, using 2- to 4-months-old plants from exposed and non-exposed populations. Paraquat was applied at 0-1600 g/ha for Virginia pepperweed and at 0-4800 g/ha for horseweed. The paraquat dose that reduced shoot dry weight by 50% (ED₅₀) was estimated for each population. Resistant populations of horseweed had ED₅₀ values 25 to 35 times higher than susceptible populations. A resistant population of Virginia pepperweed had an ED₅₀ 10 times higher than susceptible populations..

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