Herbicide-tolerant canola: weed control and yield comparisons in western Canada

Field experiments were conducted at five western Canadian locations in 1996 and 1997 to compare weed control and canola (Brassica napus L.) seed yields in the three major herbicide-tolerant canola (HTC) systems. The main objective of this study was to determine if significant weed control and yield advantages could be expected by using herbicides "designated" for HTC compared 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 yield advantages were restricted to the Lacombe and Lethbridge sites and ranged from 13 to 39% increases over the sethoxydim plus ethametsulfuron treatments. Among the HTC, weed control was usually greatest with glyphosate, followed by imazethapyr/imazamox, and then glufosinate. Glufosinate efficacy was often restricted due to advanced growth stages on some weeds. The standard treatment of sethoxydim plus ethametsulfuron did not provide better weed control than glyphosate, but in some cases did improve weed control compared to imazethapyr/imazamox or glufosinate. The HTC provide growers with new opportunities for the control of difficult weeds along with the option to employ in-crop herbicides with new modes of action in canola.