Field studies were conducted to evaluate weed control in herbicide-resistant canola in Georgia. The resistant canola cultivars and respective herbicides were ‘Pioneer 45A76’ and imazamox, ‘Hyola 357RR’ and glyphosate, and ‘2573 Invigor’ and glufosinate. Weed seed of Italian ryegrass and wild radish were sown simultaneously in October with canola and control of these species was evaluated along with other naturally occurring weeds. Herbicide treatments for the respective herbicide-resistant canola cultivar were imazamox at 0.035 and 0.071 kg ai/ha, glyphosate at 0.84 and 1.64 kg ae/ha, and glufosinate at 0.5 and 1.0 kg ai/ha. Herbicides were applied at one– two-leaf (LF) and three–four-LF canola stages. There was no significant injury to any canola cultivar as a result of herbicide rate or timing of application. By midseason (February), imazamox effectively controlled wild radish, henbit, and shepherd's-purse at both rates and at both timings. When applied to three–four-LF canola, the higher rates of glyphosate and glufosinate were required to provide 75% or greater control of Italian ryegrass, wild garlic, and henbit. Glufosinate did not adequately control wild radish at either rate or application timing. Greenhouse experiments provided similar results.
Nomenclature: Glufosinate; glyphosate; imazamox; henbit, Lamium amplexicaule L. #3 LAMAM; Italian ryegrass, Lolium multiflorum Lam. # LOLMU; wild garlic, Allium vineale L. # ALLVI; wild radish, Raphanus raphanistrum L. # RAPRA; shepherd's-purse Capsella bursa-pastoris (L.) Medicus., # CAPBP; and canola, Brassica napus L. # BRSNS, ‘Pioneer 45A76’, ‘Hyola 357RR’, and ‘2573 Invigor’.
Additional index words: Canola injury, canola yield, susceptibility to herbicides, herbicide resistance, herbicide tolerance.
Abbreviations: LF, leaf stage of growth; DAP, days after planting; IRC, imidazolinone-resistant canola.