Agronomists name herbicide-resistant weeds as top threat

Glyphosate-resistant kochia is everywhere on the Prairies, glyphosate-resistant waterhemp has arrived in Manitoba and gyphosate-resistant downy brome was found in southern Alberta. While herbicide resistance has been an issue for decades, resistance to glyphosate – an important tool for minimum tillage and for herbicide-tolerant canola – has elevated the economic risk.

In a Canola Council of Canada (CCC) survey of agronomy providers in August 2022, respondents ranked herbicide-resistant weeds number one when asked, “What canola agronomic risk factors are likely to be the greatest concerns for your farmer customers over the coming five years?” They could make more than one selection from a long list. Overall, 68 per cent chose herbicide-resistant weeds. It was the top selection in Alberta and Saskatchewan by a wide margin. Manitoba agronomy providers had it in second place, behind increased insect pressure.

As a result of the survey, CCC agronomy specialists will focus more on herbicide-resistant weeds prevention and management messages in 2023. Agronomy providers and farmers can already find many resources on integrated weed management to reduce the risk and spread of herbicide-resistant weeds, and a good first stop is “Integrated weed management: Best practices” in the weeds section at canolawatch.org/fundamentals.

Room for improvement

The survey asked an open-ended question, “In general, what agronomic practices are canola farmers most likely to get wrong?” Out of the 330 agronomy providers surveyed, 104 gave answers that fit the nutrient management theme which was the most common response.

Many just said “fertilizer” or “fertility”. Some were more specific. Here are a few answers:

• “At least in my area, soil testing and using fertility recommendations based on the results is not
  common practice.”
• “Knowing how much of what fertilizer is needed to grow a 60-bushel crop.”
• “Unbalanced fertility programs. Too much focus on nitrogen and not enough on phosphorus, potassium, sulphur or micros in some circumstances.”

Plant establishment was another common theme, especially related to seeding rate, depth or date. The ultimate goal is five to eight plants per square foot emerging uniformly. Based on survey responses, agronomy providers see opportunities to improve.

Support for CCC agronomy priorities

The survey asked 330 agronomy providers to share their views on the Canola Council of Canada’s five agronomy priorities.

Canola diseases need more attention

Canola diseases, especially sclerotinia stem rot, blackleg and clubroot, remain major yield robbers. They are, for the most part, manageable with fungicides (especially for sclerotinia stem rot and somewhat for blackleg), crop rotation (especially for blackleg and clubroot) and cultivar resistance (for blackleg, clubroot and somewhat for sclerotinia stem rot). Yet CCC agronomy specialists were surprised how little the issue came up in the survey. For the risk factors question where herbicide-resistant weeds ranked first, increased disease pressure ranked fourth.

In the open-ended question about what farmers are most likely to get wrong, only 26 of 330 respondents mentioned anything related to disease management. When asked “What canola seed traits do you make a point of recommending for farmers in your area?”, respondents were allowed to check as many as they wanted from the list. Pod shatter was tops at 84 per cent. Days to maturity specific to the local season was second. Use clubroot resistance was third, with 66 per cent, and rotate blackleg R genes was fifth, with 42 per cent.

When asked an open-ended question, “What is one change farmers can adopt to make the biggest improvement in their canola yield?”, over half the answers had to do with nutrient management, crop rotation or plant establishment. Disease management was way down the list, with five per cent saying fungicide use and another five per cent saying disease management, in general.

“The role disease has on yield may be undervalued,” says CCC agronomy specialist Ian Epp. “Diseases take the top end off yield in many canola fields.”

Harvest loss management can be hard

As part of the survey, the CCC wanted to know what agronomy providers thought of the five CCC agronomy priorities:

• Use 4R nutrient management
• Choose the best canola seed traits for each field
• Achieve a uniform five to eight plants per square foot
• Identify and management the top yield robbers in each field
• Harvest all seeds and deliver them at No.1 grade

When asked which ones they actively promote to customers, the first four scored high – three in the 70s and one, yield robbers, at 80 per cent. However, only 49 per cent actively promote harvest loss management. And when asked to choose a number between one and five to indicate how easy each priority is to apply at the farm level, harvest loss management ranked the lowest at 3.3. (See the table.)

For the question about one change that would have the biggest improvement in yield, reducing harvest loss rarely came up.

“I think we may have a huge disconnect on harvest management,” says Curtis Rempel, CCC vice president.

Setting combines to reduce loss is complicated by various influencing adjustments – sieve spacing, concave spacing, header settings, rotor speed, fan speed, ground speed – done in response to changing harvest conditions. This does take some extra time. The CCC agronomy team, when interpreting the results, acknowledge a need for more on-farm expertise in this area, which could provide a consulting opportunity for agronomists beyond their typical services.

CCC the source for canola agronomy

When asked “Who provides most of your canola agronomy information,” the most common answer was the CCC. Agronomy providers could choose more than one option from a long list, and 79 per cent chose the CCC. Next were “my employer/my business” at 52 per cent and “CCA credited events and courses” at 43 per cent.

However, when asked more specific questions about CCC products, only 46 per cent knew about the online Canola Encyclopedia. And while a high percentage had heard of Canola Watch, only about 60 per cent were subscribers. This will inspire some focused Canola Watch promotion in 2023, and extra attention to raise awareness of valuable CCC agronomy resources. (See the sidebar.)

Agronomy wins

Respondents showed good alignment with key best practices:

Target stand: The CCC recommends a stand of five to eight plants per square foot. Some seed companies recommend five to seven. Ninety-three per cent of respondents recommend one of those two options.

4R designation: When asked, “Do you have the 4R designation through either the CCA program or Fertilizer Canada program?”, 44 per cent said yes and another 39 per cent said they plan to within the next two years.

Swath timing: The CCC recommends swathing once main stems show at least 60 per cent seed colour change. This timing is important for yield and quality. In the survey, 68 per cent of respondents say they recommend 60 per cent or more. Of the six per cent who chose “other”, most specified an even later cut time. Fifteen per cent recommend 51-59 per cent seed colour change.