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.

Herbicide tank mixtures to control co-existing glyphosate-resistant Canada fleabane and giant ragweed in soybean

“…This study builds upon previous work in our research group on the management of GR biotypes of Canada fleabane and giant ragweed in soybean with two-way glyphosate tank mixtures applied PP (Vink et al 2012a;Byker et al 2013aByker et al , 2013cFollings et al 2013a). However, due to the presence of multiple resistant biotypes in both species (Byker et al 2013c;Follings et al 2013b) and to observations of varying levels of 2,4-D tolerance in Canada fleabane (Ford et al 2014), we were interested in identifying three-way tank mixtures that could potentially delay further resistance development (Beckie 2011).…”

“…A total of ten field experiments (five separate locations with GR Canada fleabane and five separate locations with GR giant ragweed) were conducted over a two year period (2013 and 2014) on various farms in southern Ontario (Table 1) where GR biotypes of these species were known to be present (Vink et al 2012b;Byker et al 2013c;Follings et al 2013b). Treatments were arranged in a randomized complete block with four replications, with plots 2 m wide by 10 m long.…”

“…While at other locations, the control of these species was around 50% four WAT using glyphosate + cloransulam (Vink et al 2012a;Byker et al 2013a). The low level of control in these instances could be due to the presence of multiple resistant (glyphosate and cloransulam) biotypes of Canada fleabane (Byker et al 2013c) and giant ragweed (Follings et al 2013b), further complicating weed management decisions. As a result, Ontario soybean growers need more options for controlling GR Canada fleabane and GR giant ragweed.…”

“…Unfortunately, these species could be present in the same field (Westhoven et al 2008). In addition, multiple resistant biotypes are known to share roughly the same geographic area (Byker et al 2013c;Follings et al 2013b). Therefore, this research was conducted to evaluate two-and three-way PP herbicide tank mixtures that could control both GR Canada fleabane and GR giant ragweed if they were present in the same soybean field.…”

“…For example, in 2008, a giant ragweed biotype was found in Essex County that survived multiple glyphosate applications in soybean (Vink et al 2012b); in 2010, GR Canada fleabane was identified by screening plants grown from seed collected from weed escapes in Essex county GR soybean fields (Byker et al 2013c). Since these GR biotypes were first identified, subsequent field surveys have documented that GR giant ragweed is present in over 80 locations across seven Ontario counties (Vink et al 2012b;Follings et al 2013b) and GR Canada fleabane is present in at least 155 locations across eight Ontario counties (Byker et al 2013c).…”