Occurrence of glyphosate and cloransulam resistant Canada fleabane (Conyza canadensis L. Cronq.) in Ontario

Abstract

Byker, H. P., Soltani, N., Robinson, D. E., Tardif, F. J., Lawton, M. B. and Sikkema, P. H. 2013. Occurrence of glyphosate and cloransulam resistant Canada fleabane ( Conyza canadensis L. Cronq.) in Ontario. Can. J. Plant Sci. 93: 851–855. Canada fleabane is the second documented glyphosate-resistant (GR) weed species in Ontario, Canada. In 2010, the first eight GR Canada fleabane populations were identified in Essex County. In 2011 and 2012, an expanded survey was conducted to identify the occurrence of GR and cloransulam-resistant populations in Ontario. Seed was collected from field weed escapes in the early fall and sprayed in the greenhouse with 900 g a.e. ha−1 of glyphosate at the 10-cm rosette stage. Ninety-three and 54 additional sites were confirmed in 2011 and 2012, respectively. There are now 155 sites with confirmed GR Canada fleabane in Ontario in the counties of Elgin, Essex, Haldimand, Huron, Kent, Lambton, Middlesex, and Niagara region. Twelve and seven sites were identified with multiple resistant Canada fleabane (glyphosate and cloransulam) in 2011 and 2012, respectively in Elgin, Essex, Kent, Lambton, and Middlesex counties. This is the first survey documenting the occurrence of glyphosate-resistant and multiple resistant (glyphosate and cloransulam) Canada fleabane in Ontario and its distribution.