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1 October 2008 Field-Scale Time of Weed Removal in Canola
K. Neil Harker, John T. O'Donovan, George W. Clayton, John Mayko
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Abstract

Field-scale experiments were conducted at several western Canada locations to determine the importance of early weed removal over variable landscapes. In eight of 10 cases, imidazolinone-resistant (IR) canola yield decreased linearly as herbicide application (15/15 g/ha imazamox/imazethapyr or 15/15 g/ha imazamox/imazethapyr plus 150 g/ha clopyralid) was delayed beyond the one- to two-leaf stage. In two of 10 cases, canola oil content also decreased as herbicide treatment was delayed. Canola yields at all environments (location by year combinations) averaged 2,073, 1,872, or 1,650 kg/ha when treated at the one- to two-, three- to five-, or six- to seven-leaf stage, respectively. Assuming canola prices from a low of $250/t to a high of $650/t, growers could lose $50 to $131/ha, respectively, by delaying herbicide application from the one- to two- to the three- to five-leaf stage, or $106 to $275/ha, respectively, by delaying herbicide application from the one- to two- to the six- to seven-leaf stage.

Nomenclature: Clopyralid; imazamox; imazethapyr; canola, Brassica napus L. ‘46A73’

K. Neil Harker, John T. O'Donovan, George W. Clayton, and John Mayko "Field-Scale Time of Weed Removal in Canola," Weed Technology 22(4), 747-749, (1 October 2008). https://doi.org/10.1614/WT-08-107.1
Received: 29 July 2008; Accepted: 1 September 2008; Published: 1 October 2008
KEYWORDS
critical period
duration of competition
economic loss
late spraying
oilseed rape
spray timing
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