HRAC GROUP 5 (LEGACY C1 C2) RESISTANT WITCHGRASS
(Panicum capillare)

PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2)

Canada, Ontario

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INTRODUCTION WITCHGRASS Witchgrass (Panicum capillare) is a monocot weed in the Poaceae family.  In Ontario this weed first evolved resistance to Group 5 (Legacy C1 C2) herbicides in 1981 and infests Corn (maize), and Cropland.   Group 5 (Legacy C1 C2) herbicides are known as PSII inhibitors - Serine 264 Binders (Inhbition of Photosynthesis at PSll - Serine 264 Binders ).  Research has shown that these particular biotypes are resistant to atrazine and they may be cross-resistant to other Group 5 (Legacy C1 C2) 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 Witchgrass Species Panicum capillare Group PSII inhibitors - Serine 264 Binders HRAC Group 5 (Legacy C1 C2) Herbicides atrazine Location Canada, Ontario Year 1981 Situation(s) Corn (maize), and Cropland Contributors - (Alphabetically) Clarence Swanton  Edit this Case  |  Add New Case of Resistance  |  Add Note

NOTES ABOUT THIS BIOTYPE AREAS FOUND Clarence Swanton Found in Waterloo, Grey, and York counties. Edit this Note  |  Add New Note   GENERAL Hugh Beckie G. R. Stephenson, M. D. Dykstra, R. D. McLaren, and A. S. Hamill. 1990. Agronomic practices influencing triazine-resistant weed distribution in Ontario. Weed Technol. 4:199-207. Edit this Note  |  Add New Note

ACADEMIC ASPECTS Confirmation Tests Field, Greenhouse, and Laboratory trials comparing a known susceptible Witchgrass biotype with this Witchgrass 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 5 resistant Witchgrass 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 5 (Legacy C1 C2) resistant Witchgrass from Ontario please update the database.   Edit Case  |  Add Note  |  Add Article  |  Add New Case  |  Help

CONTRIBUTING WEED SCIENTISTS CLARENCE SWANTON University Of Guelph Dept. Of Crop Science Ontario Agricultural College PO Box 249 Guelph, N1G 2W1, Ontario Canada Email Clarence Swanton

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 Clarence Swanton for providing detailed information.

Herbicide Resistant Witchgrass Globally (Panicum capillare) Herbicide Resistant Witchgrass Globally (Panicum capillare) Drag a column header and drop it here to group by that column Herbicide Resistant Witchgrass Globally (Panicum capillare) # Country Country StateName FirstYear Situation Active Ingredients CountryID Site of Action WeedID Species CommonName ResistID 1 Canada (Ontario) Canada Ontario 1981 Corn (maize), and Cropland atrazine 7 PSII inhibitors - Serine 264 Binders ( HRAC Group 5 (Legacy C1 C2) 121 Panicum capillare Witchgrass 63

Literature about Similar Cases

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Clements, D. R. ; DiTommaso, A. ; Darbyshire, S. J. ; Cavers, P. B. ; Sartonov, A. D.. 2004. The biology of Canadian weeds. 127. Panicum capillare L. Canadian Journal of Plant Science 84 : 327 - 341.

Panicum capillare, witch grass, is an annual grass native to North America that infests field crops, small grains, grasslands, and a variety of other habitats. High seed production, a persistent seed bank, a tumble-weed seed-dispersing mechanism, and the ability to tolerate some herbicides contribute to the success of P. capillare in these habitats. Despite the widespread presence of P. capillare in crops, its actual impact on crop yield is not well documented. It is an additional host for several insect pests (e.g. cereal aphids) and diseases attacking crop species..

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