Field experiments were conducted at five western Canadian locations in 1996
and 1997 to compare weed control and canola (Brassica napus L.) seed yield
s in the three major herbicide-tolerant canola (HTC) systems. The main obje
ctive of this study was to determine if significant weed control and yield
advantages could be expected by using herbicides "designated" for HTC compa
red to a more "standard" application of sethoxydim plus ethametsulfuron. In
3 of 10 site-years, glyphosate in Quest canola and imazethapyr/imazamox in
45A71 canola provided a yield advantage over the standard treatment. The y
ield advantages were restricted to the Lacombe and Lethbridge sites and ran
ged from 13 to 39% increases over the sethoxydim plus ethametsulfuron treat
ments. Among the HTC, weed control was usually greatest with glyphosate, fo
llowed by imazethapyr/imazamox, and then glufosinate. Glufosinate efficacy
was often restricted due to advanced growth stages on some weeds. The stand
ard treatment of sethoxydim plus ethametsulfuron did not provide better wee
d control than glyphosate, but in some cases did improve weed control compa
red to imazethapyr/imazamox or glufosinate. The HTC provide growers with ne
w opportunities for the control of difficult weeds along with the option to
employ in-crop herbicides with new modes of action in canola.