Tolerance of annual canarygrass (Phalaris canariensis L.) to combinations of MCPA, clopyralid, fluroxypyr and florasulam

Abstract

May, W. E., Johnson, E. N., Sapsford, K. L., Stevenson, F. C., Lafond, G. P., Holzapfel, C. B. and Holm, F. A. 2014. Tolerance of annual canarygrass (Phalaris canariensis L.) to combinations of MCPA, clopyralid, fluroxypyr and florasulam. Can. J. Plant Sci. 94: 701–708. Annual canarygrass (Phalaris canariensis L.) is a cereal crop that is primarily grown on the Canadian prairies as feed for caged birds. To widen the spectrum of herbicide options for producers, two experiments were conducted with the following nine herbicide treatments (application rates in parentheses expressed as g a.i. ha−1): weed-free control; single and double applications of MCPA (560)+clopyralid (100) (Curtail M); MCPA (562)+fluroxypyr (108) (Trophy); and MCPA (560)+clopyralid (100)+fluroxypyr (144) (Prestige); florasulam (5)+MCPA (420) (Frontline); difenzoquat (700)+MCPA (560)+clopyralid (100) (Avenge+Curtail M); and a single application of difenzoquat (700). Experiment 2 included the same herbicide treatments in factorial combinations with two application times; crop growth stages of two to three leaf (2–3 lf) and four to five leaf (4–5 lf). Experiments were conducted at Indian Head, Scott, and Saskatoon, SK, in 2001 to 2003. In exp. 1, difenzoquat caused up to 30% crop injury when combined with MCPA+clopyralid at the 2× rate, but improved crop yield relative to other herbicides because it reduced yield interference from wild oat infestations at Indian Head in 2002. In exp. 2, the 2× rate of florasulam+MCPA resulted in the greatest visual injury, with higher levels recorded at the 2–3 lf; however, seed yield reduction was greater when applied at the 4–5 lf. In summary, annual canarygrass was tolerant to combinations of MCPA, clopyralid, and fluroxypyr, herbicides which control important weed species in prairie fields.