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Critical period of weed control in spring canola

Published online by Cambridge University Press:  20 January 2017

Steven G. Martin ,
Rene C. Van Acker  and
Lyle F. Friesen
Steven G. Martin
Affiliation:
Department of Plant Science, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
Lyle F. Friesen
Affiliation:
Department of Plant Science, University of Manitoba, Winnipeg, MB, R3T 2N2, Canada
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Abstract

The critical period of weed control is the portion of the life cycle of a crop during which it must be kept weed-free to prevent yield loss due to weed interference. The advent of herbicide-resistant canola (Brassica napus L.) varieties in western Canada has meant that there are now more options for postemergence weed control in canola, and this has prompted increased interest in identifying the optimum timing for weed control in this crop. A critical period experiment was conducted at three locations in southern Manitoba in 1998 and 1999, and it consisted of two sets of treatments. In the first set of treatments, the crop was kept weed-free for increasing lengths of time to determine when emerging weeds would no longer reduce crop yield. In the second set of treatments, weeds were permitted to grow in the crop for increasing lengths of time to determine when weeds emerging with the crop began irrevocably to reduce crop yield. Results of the experiments indicated that canola must be kept weed-free in most cases until the four-leaf stage of the crop (17–38 days after crop emergence [DAE]) and, in one early-seeded experiment, until the six-leaf stage of the crop (41 DAE), in order to prevent >10% yield loss. After the four- to six-leaf stage of the canola crop, few weeds emerged, and late-emerging weeds accumulated little shoot biomass. Weeds needed to be removed by the four-leaf stage of the crop (17–38 DAE) to prevent >10% yield loss due to weed interference. In all but the early-seeded experiment, the critical weed-free period and the critical time of weed removal overlapped, such that a single weed removal at the four-leaf stage of the crop would have been sufficient to prevent >10% yield loss. This information will be useful for providing weed control recommendations to canola producers.

Keywords

Diquatglufosinateglyphosateterbufosbarnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCGcanola, Brassica napus L. BRSNS, ‘Innovator’common hempnettle, Galeopsis tetrahit L. GAETEcommon lambsquaters, Chenopodium album L. CHEALcommon purslane, Portulaca oleraceae L. POROLdandelion, Taraxacum officinale Weber in Wiggers TAROFfield pennycress, Thlaspi arvense L. THLARgreen foxtail, Setaria viridis (L.) Beauv. SETVIquackgrass, Elytrigia repens (L.) Nevski AGRREredroot pigweed, Amaranthus retroflexus L. AMAREroundleaved mallow, Malva pusilla Sm. MALPUsmartweed, Polygonum persecaria L. POLPEvolunteer barley, Hordeum vulgare L. HORVXvolunteer flax, Linum usitatissimum L. LINUSvolunteer wheat, Triticum aestivum L. TRZASwild buckwheat, Polygonum convolvulus L. POLCOwild mustard, Brassica kaber (DC.) L. C. Wheeler SINARwild oat, Avena fatua L. AVEFAyellow foxtail, Setaria pumila (Poir.) Roem & Schult. SETLUWeed interferencecompetitiontime of removalcritical period
Type
Research Article
Information
Weed Science , Volume 49 , Issue 3 , June 2001 , pp. 326 - 333
Copyright
Copyright © Weed Science Society of America 

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