[UPDATED: Jan. 14, 2021] Q: Should weed populations in my field affect my canola decision?
A: When selecting canola varieties for your operation in 2021, yield potential and pod integrity are front of mind. However, different varieties utilize different herbicide-resistance traits, and this, too, should be considered.
Canola varieties utilizing glufosinate (LibertyLink or LL), glyphosate (Roundup Ready or RR), sulfonylurea (SU) and Clearfield imidazolinone (IMI) traits can be an agronomic fit depending on your operation and the weeds present in your fields.
Glyphosate, especially TruFlex varieties, are a great tool for growers who have significant late-flush weeds or grassy weed populations. TruFlex varieties can be applied later into the season, from cotyledon up to first flower, ensuring late-germinating weeds will not establish late and set seed. For fields with significant grassy weed and wild oat pressure, glyphosate-tolerant varieties are an excellent agronomic fit.
Varieties tolerant to glufosinate have yielded exceptionally well across Western Canada. For optimal control, glufosinate should be sprayed in the heat of day with increased water volumes. Though some growers will be tempted to reduce spray volumes to stretch acres applied during the busy spray season, applying spray solution with at least 15 gallons per acre will help to maximize herbicide efficacy.
*Glufosinate is a Group 10 herbicide that works by contact, and adequate coverage is important. Spraying at reduced volumes can limit coverage and could require a followup application to control missed weeds, reducing yield and is an added cost for an additional pass.
IMI-resistant varieties are often used as a rotational break for fields with significant volunteer RR or LL canola populations. These varieties also carry non-GMO oil contract premiums that can be priced into your operation.
Though an agronomic fit to control volunteer canola, if your operation has a history of Group 2-resistant weeds, other herbicide-resistance systems are a better fit. Sulfonylurea varieties are relatively new to Western Canada, use different Group 2 herbicide-resistance traits and are also non-GMO. For both IMI and SU varieties, ensure plants reach proper staging before applying to reduce crop injury.
When selecting varieties for your operation, it is important to consider the yield potential, herbicide tolerance and agronomics of the varieties as part of a multi-year management strategy. Consider local trial data when selecting the right variety for your farm and always use registered tank mixes with additional active ingredients, when possible, to reduce selection pressure for herbicide resistance on your fields.
*Update: The article previously stated glufosinate as a Group 14 herbicide.
Derek Flad, CCA, is a manager of agronomic services for Nutrien Ag Solutions in southern Alberta.