Unprecedented flooding and excessive soil moisture conditions in 2011 for parts of Manitoba and Saskatchewan have resulted in an unprecedented number of acres going unseeded. With a record acreage of canola seeded in western Canada in 2010 and harvest losses estimated at 3% to 10%, a large proportion of weeds in those unseeded acres will be volunteer canola. At this point in the growing season, many of those canola plants are coming out of full flower and viable seed is starting to occur.
So what to do now? These plants probably did help draw water out of the soil and may be used as a snow catch stubble for winter cereal planting, but should be destroyed before viable seed is set. Volunteer canola in the field at this point is a weed that could dramatically impact your canola crops in the future, as it may be infected with blackleg or sclerotinia, adding additional inoculum to the field to infect subsequent crops. As well, it could potentially add thousands of viable seeds and resulting plants that you will need to control in the future.
Growers in this situation should spray out volunteer canola and other weeds in the field with an application of glyphosate plus a Group 4 (phenoxy) product or other suitable product. With pollen flow, growers switching systems, shorter rotations of different systems, and of course adventitious presence, never assume a volunteer crop is completely Roundup Ready or Liberty Link or Clearfield. Use more that one herbicide to control the volunteers.
After termination of the weed/canola stand, she suggests seeding a fall planted cereal such as winter wheat or fall rye into the remaining stubble within recommended provincial crop insurance seeding timelines. Alternatively the land could be maintained as chemical fallow for the remainder of the year.