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Herbicide Timing and Rate Effects on Weed Management in Three Herbicide-Resistant Canola Systems

Published online by Cambridge University Press:  20 January 2017

K. Neil Harker ,
George W. Clayton ,
John T. O'Donovan ,
Robert E. Blackshaw  and
F. Craig Stevenson
K. Neil Harker*
Affiliation:
Agriculture and Agri-Food Canada, Lacombe Research Centre, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada
George W. Clayton
Affiliation:
Agriculture and Agri-Food Canada, Lacombe Research Centre, 6000 C & E Trail, Lacombe, AB T4L 1W1, Canada
John T. O'Donovan
Affiliation:
Agriculture and Agri-Food Canada, Beaverlodge Experimental Farm, Box 26, Beaverlodge, AB T0H 0C0, Canada
Robert E. Blackshaw
Affiliation:
Agriculture and Agri-Food Canada, Lethbridge Research Centre, Box 3000, Lethbridge, AB T1J 4B1, Canada
F. Craig Stevenson
Affiliation:
142 Rogers Road, Saskatoon, SK S7N 3T6, Canada
*
Corresponding author's E-mail: harkerk@agr.gc.ca
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Abstract

Herbicide-resistant canola dominates the canola market in Canada. A multiyear field experiment was conducted at three locations to investigate the effect of time of weed removal (two-, four-, or six-leaf canola) and herbicide rate (50 or 100% recommended) in three herbicide-resistant canola systems. Weeds were controlled in glufosinate-resistant canola (GLU) with glufosinate, in glyphosate-resistant canola (GLY) with glyphosate, and in imidazolinone-resistant canola (IMI) with a 50:50 mixture of imazamox and imazethapyr. Canola yields were similar among the three canola cultivar–herbicide systems. Yields were not influenced by 50 vs. 100% herbicide rates. Timing of weed removal had the greatest effect on canola yield, with weed removal at the four-leaf stage giving the highest yields in most cases. Percent dockage was often greater for GLU and IMI than for GLY. In comparison with the other treatments, dockage levels doubled for GLU after application at 50% herbicide rates. The consistency of monocot weed control was usually greater for GLY than for GLU or IMI systems. However, weed biomass data revealed no differences in dicot weed control consistency between IMI and GLY systems. Greater dockage and weed biomass variability after weed removal at the six-leaf stage or after low herbicide rates suggests higher weed seed production, which could constrain the adoption of integrated weed management practices in subsequent years.

Keywords

Glufosinateglyphosateimazamoximazethapyrcanola, Brassica napus L.GMOherbicide-tolerant canolaintegrated weed managementtime of weed removalGLU, glufosinate-resistant canolaGLY, glyphosate-resistant canolaIMI, imidazolinone-resistant canolaIWM, integrated weed managementPOST, postemergence.
Type
Research
Information
Weed Technology , Volume 18 , Issue 4 , December 2004 , pp. 1006 - 1012
Copyright
Copyright © Weed Science Society of America 

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