Glyphosate- or Auxinic-Resistant Kochia and Russian Thistle Prairie Surveys

Researcher(s): Shaun Sharpe, AAFC; Julia Leeson, Charles Geddes, AAFC; Chris Willenborg, University of Saskatchewan; Hugh Beckie, AAFC; Robert Gulden, University of Manitoba; Linda Hall, Keith Topinka, University of Alberta
Term: 5 years, ending Feb 1, 2023
Status: Completed
SaskCanola Investment: $20,000
Total Project Cost: $87,800
Funding Partners: AWC, MPSG, MCA, SPG, SWDC, WGRF

Grower Benefits

Kochia is a prolific seed producer so best management practices that limit biomass and reduce the soil seedbank by limiting seed return are advisable
Crops such as spring oats, field pea, canola and spring wheat are among the most tolerant to kochia interference
In Saskatchewan, glyphosate resistant kochia was found in 87% of samples and dicamba resistant kochia was found in 45% of samples. Assuming all kochia is resistant to ALS-inhibitors (Group 2), triple resistant kochia was found in 40% of Saskatchewan samples.

Project Summary

Short Report PDF: Glyphosate- or Auxinic-Resistant Kochia and Russian Thistle Prairie Surveys

Kochia is a problematic tumbleweed which infests agricultural and disturbed areas on the Prairies. Kochia has evolved resistance to several modes of action including ALS-inhibiting herbicides (Group 2), glyphosate (Group 9), and synthetic auxins (Group 4). The study objective was to survey glyphosate-resistant and dicamba-resistant kochia distributions in Manitoba, Saskatchewan, and Alberta. A randomized stratified survey was conducted post-harvest, starting in early October. Manitoba was surveyed in 2018, Saskatchewan in 2019, and Alberta in 2021. Samples were screened with discriminating doses of glyphosate (900 g ae ha-1) or dicamba (280 g ae ha-1). The incidence of glyphosate-resistant (GR) kochia increased substantially from previous surveys. GR kochia was found in 58% of Manitoba samples, 87% of Saskatchewan samples, and 78% of Alberta samples. Dicamba-resistant (DR) kochia was found at 1% of Manitoba sites, 45% of Saskatchewan sites, and 28% of Alberta sites. This documents the first instance of DR kochia in Manitoba. Assuming all kochia is resistant to ALS-inhibitors, triple-resistant kochia was present in 40% of Saskatchewan samples (n=255), <1% of Manitoba samples (n=300), and 10% (n=314) of Alberta samples. Additional screening showed 44% of Alberta samples were fluroxypyr-resistant and 25% were triple-resistant. Herbicide-resistant kochia has become more prevalent on the Prairies. Seedbanks should be depleted to reduce selection pressure on herbicides. Cultural methods to rapidly achieve canopy closure should be integrated with pre-emergence herbicides to prevent escapes after herbicide efficacy wanes. Kochia is present in many environments outside of cropped land so mitigation procedures for tumbleweeds are advised.