Glyphosate-resistant Canada fleabane (Conyza canadensis (L.) Cronq.) in Ontario: Distribution and Control in Soybean (Glycine Max (L.) Merr.)

• Main Author: Byker, Holly P.
• Other Authors: Sikkema, Peter H.
• Language: en
• Published: 2013
• Subjects: Canada fleabane; glyphosate; biologically effective rate of glyphosate; resistance; multiple resistance; cloransulam; dicamba; soybean; survey; preplant herbicides; postemergence herbicides
• Online Access: http://hdl.handle.net/10214/6582

Canada fleabane is the second glyphosate-resistant (GR) weed species to be confirmed in Ontario. In 2010, GR populations were identified at eight sites in Essex County. In 2011 and 2012, 147 additional sites across eight counties were confirmed to be resistant. Twelve and seven sites were identified with multiple resistance (glyphosate and cloransulam) in 2011 and 2012, respectively, across five counties. In soybeans, preplant tankmixes of glyphosate (900 g a.e.ha-1) plus saflufenacil (25 g a.i. ha-1), saflufenacil/dimethenamid-p (245 g a.i. ha-1), metribuzin (1120 g a.i. ha-1), or flumetsulam (70 g a.i. ha-1) provided greater than 87% up to 8 weeks after application (WAA). Glyphosate rates 21 to 48X the label rate (900 g a.e. ha-1) were required for 95% control. Postemergence tankmixes did not provide acceptable control. In dicamba-tolerant soybean, dicamba applied preplant at 600 g a.e. ha-1 provided the most consistent control of GR Canada fleabane. === Monsanto Canada Inc., Grain Farmers of Ontario, Agricultural Adaptation Council