Herbicide Strategies for Control of Glyphosate-Resistant and -Susceptible Kochia (Bassia scoparia) in Chemical Fallow and Spring Wheat

  • Author / Creator
    Torbiak, Alysha
  • Kochia [Bassia scoparia (L.) A.J. Scott], the first known glyphosate-resistant weed in western Canada, is an abundant and troublesome summer annual tumbleweed. Yet, knowledge gaps exist in kochia management, specifically as to what herbicide and herbicide mixes are effective to control glyphosate-resistant (GR) and glyphosate-susceptible (GS) kochia in chemical fallow and spring wheat (Triticum aestivum L.). Kochia’s tolerance to saline soils, drought, and heat, as well as its ability to emerge early with multiple flushes, rapid growth, and late maturation, all contribute to its reproductive success and geographical expansion. This thesis research consisted of two field studies conducted in Alberta, Canada, from 2013 to 2015 and aimed to discover effective herbicidal control for GR and GS kochia in chemical fallow and spring wheat in western Canada. The most consistent control in chemical fallow (≥80% visual control in all environments with ≥80% biomass reduction in 2014) was observed with glyphosate + dicamba, glyphosate + dicamba/diflufenzopyr, glyphosate + saflufenacil, and glyphosate + carfentrazone + sulfentrazone. Reduced efficacy was observed for several herbicide mixtures when they were applied to GR compared with GS kochia accessions. Effective modes of action mixed with glyphosate include synthetic auxins (group 4), a combination of a synthetic auxin and an auxin transport inhibitor (group 19), or protoporphyrinogen oxidase inhibitors (group 14). The most effective and consistent treatments for kochia management in spring wheat included sulfentrazone applied pre-emergence and fluroxypyr/bromoxynil/2,4-D or pyrasulfotole/bromoxynil applied post-emergence. All of these treatments resulted in ≥90% visible control in all environments and ≥90% kochia biomass reduction compared with the untreated control in Lethbridge 2014 and 2015.

    MCPA/dichlorprop-p/mecoprop-p, dicamba/2,4-D/mecoprop-p, and dicamba/fluroxypyr resulted in acceptable control among environments (≥80% visible control in all environments and ≥80% kochia biomass reduction in Lethbridge 2014 and 2015); however, the latter two options caused unacceptable (>10%) wheat visible injury in Coalhurst 2014. Confirmations of auxinic herbicide-resistant kochia in western Canada, partly due to their increase of use on GR kochia in spring grains, will limit these herbicide options. If designed appropriately, an integrated herbicide program for kochia including mixing, rotating, and layering alternative herbicide modes of action could help mitigate further selection for herbicide resistance.

  • Subjects / Keywords
  • Graduation date
    Fall 2022
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.