Improving the Consistency of Glyphosate-resistant Canada fleabane (Conyza canadensis) Control with Saflufenacil: Distribution and Control in Soybean (Glycine max)

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Date
2016-05-11
Authors
Budd, Christopher Murray
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Publisher
University of Guelph
Abstract

In 2010, glyphosate-resistant (GR) biotypes of Canada fleabane were first confirmed in Essex County, Ontario. From surveys conducted in 2010 to 2015, inclusive, GR Canada fleabane has now been confirmed in 30 counties and multiple-resistant biotypes (glyphosate and cloransulam-methyl) in 22 counties. Saflufenacil was recommended for GR Canada fleabane control in soybean, however variable control had been reported. The biologically effective rate (BER) of saflufenacil is 25 g a.i. ha-1 for 90% control eight weeks after application (WAA). At 8 WAA, the BER of metribuzin when tankmixed with glyphosate (900 g a.i. ha-1) plus saflufenacil (25 g a.i. ha-1) was 61, 261, and 572 g a.i. ha-1 for 90, 95 and 98% control, respectively. Tankmix partners with glyphosate (900 g a.i. ha-1) plus saflufenacil (25 g a.i. ha-1) were investigated, and the best three-way tankmixes were with either 2,4-D or metribuzin for full season control of multiple-resistant Canada fleabane. The optimal time of day (TOD) for controlling GR Canada fleabane with glyphosate (900 g a.i. ha-1) plus saflufenacil (25 g a.i. ha-1) was 09:00-21:00 h. GR Canada fleabane height and density were found to have a minimal effect on control with glyphosate (900 g a.i. ha-1) plus saflufenacil (25 g a.i. ha-1).

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Keywords
Soybean, Canada fleabane, Glyphosate-resistant biotypes, Saflufenacil, Biologically effective rate
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