Effect of Herbicides on Field Violet (Viola arvensis) in Direct-Seeded Spring Wheat

Abstract

The agrestal field violet, a pervasive weed in Europe, has been identified in reduced-tillage cereal fields in Alberta. The efficacy of herbicides in direct-seeded spring wheat was assessed on natural field violet infestations in Alberta in 2002 and 2003. Only fluroxypyr + 2,4-D, applied postemergence, provided control of field violet in 2002 when rainfall was limiting. Over both years, this herbicide combination reduced biomass by 59 to 69% and plant density by 83 to 91%, relative to nontreated plots. The herbicides metsulfuron, sulfosulfuron, and thifensulfuron + tribenuron only suppressed weed growth under drought conditions in 2002 but controlled the weed in 2003 when rainfall was greater, reducing plant density by 82 to 92% and rendering remaining plants sterile. Suppression was also observed with MCPA + mecoprop + dicamba in 2002 and 2003 and with metribuzin only in 2003. Effective control of field violet was conferred by a pre–crop emergence application of glyphosate at 445 g ae/ha in 2003, the only year that this treatment was evaluated. Activity of herbicides on three- to four-leaf seedlings was also evaluated in a greenhouse dose– response assay. All herbicides had greater efficacy in the greenhouse, and those that provided control in situ reduced field violet dry weight by 85% at less than the recommended rate used in field experiments. Management of field violet is possible with herbicides registered for use on spring wheat in Alberta. However, the weed does not appear to cause significant crop production losses; hence, herbicide selection should be based on knowledge of all weed species present within the field.

Phenological development of natural populations of European field pansy (Viola arvensis) in a semi‐arid Mediterranean environment

“…A similar behavior of European field pansy in wheat and oilseed rape has been reported in the literature (Degenhardt et al . , ).…”

“…In addition, the European field pansy is considered a rather easy weed species to tackle, particularly with the use of herbicides (Huggenberger & Gueguen ; Degenhardt et al . , ; Becker et al . ; Koo & Caseley ; Richardson & Zandstra ); thus, perhaps further research was not justified.…”

“…) and also in Canada (Degenhardt et al . , , ). The available information on the biology of this species, with particular reference to phenological and demographic behavior in relation to environmental parameters, remains insufficient, probably because the species is considered to be a minor threat in agroecosystems (Degenhardt et al .…”

“…The European field pansy (Viola arvensis) has occurred with increasing frequency over the last few years in Orestiada, Greece (Damalas et al 2014). According to the literature, this species is an annual weed mainly of various cereals and oilseed rape in northern Europe (Vanaga et al 2010;Salonen et al 2011;Andreasen & Stryhn 2012;Hanzlik & Gerowitt 2012), in New Zealand (Bourdôt et al 1998) and also in Canada (Degenhardt et al 2005a(Degenhardt et al , 2005b(Degenhardt et al , 2005c. The available information on the biology of this species, with particular reference to phenological and demographic behavior in relation to environmental parameters, remains insufficient, probably because the species is considered to be a minor threat in agroecosystems (Degenhardt et al 2005c).…”

“…The available information on the biology of this species, with particular reference to phenological and demographic behavior in relation to environmental parameters, remains insufficient, probably because the species is considered to be a minor threat in agroecosystems (Degenhardt et al 2005c). In addition, the European field pansy is considered a rather easy weed species to tackle, particularly with the use of herbicides (Huggenberger & Gueguen 1987;Degenhardt et al 2005aDegenhardt et al , 2005bBecker et al 2008;Koo & Caseley 2008;Richardson & Zandstra 2009); thus, perhaps further research was not justified. Information on the phenological development of this weed in response to common abiotic parameters could be useful to explain its occurrence in common production systems under usual farming practices.…”