Adventitious Presence: Volunteer Flax (Linum usitatissimum) in Herbicide-Resistant Canola (Brassica napus)

Flax is in the process of development as a crop for bio-industrial and nutraceutical products predicated on the use of genetic modification. Before genetically modified (GM) flax is commercially released, effective management practices should be developed to minimize adventitious presence (AP) of GM volunteer flax in subsequent crops. Field research was conducted at four locations during 2007 and 2008 in central Alberta to quantify and mitigate AP of volunteer flax in glufosinate-resistant (GR) and imidazolinone-resistant (IR) canola. A single preplant application of glyphosate at 1,250 g ae ha(-1) in GR canola reduced volunteer flax density from 54 to 3 plants m(-2) and seed production from 5,963 to 233 seeds m(-2). Similarly, the recommended rate of POST glufosinate (600 g ai ha(-1)) alone effectively controlled volunteer flax and reduced flax seed viability to < 8% and AP to 0.2%. A combination of preplant (glyphosate) and POST (glufosinate) at recommended rates reduced volunteer flax seed production, yield, and AP to near zero in GR canola. Glyphosate applied preplant was equally effective in IR canola, reducing volunteer flax density from 56 to 2 plants m(-2), and seed production from 5,571 to 472 seeds m(-2). Imazamox + imazethapyr applied POST at all the rates poorly controlled volunteer flax and, even in combination with preplant glyphosate, cannot be recommended for control of flax volunteers in IR canola.