Weed control options should factor into cropping plans

Q & A with an expert

Q: What do I need to think about when planning for weed management?

A: It is this time of year when acres are being locked into place for the upcoming growing season. With commodity prices currently on an upward trajectory, many different cropping options are being considered. Crops like flax, field peas and soybeans have generated more interest among growers than in other years. Weed control options should be considered when making changes to cropping plans based on commodity prices.

The following are five easy points to consider for the upcoming year:

1. Do I have any chemistries that I applied last year that may place restrictions on what crops I can grow this year? Pull out your spraying diaries from last year. Ask your crop protection provider for last year’s purchase records. The rule of thumb is five to six inches of usable rainfall is required between date of application and September 10 to ease the re-cropping restrictions on most labels. The caveat here is when a thunderstorm rolls through and the field receives two to three inches—or more—in a single rainfall. Only the first inch of rain is generally counted toward your usable rainfall. If you have questions, reach out to a crop production advisor or weed management expert.

2. Do I have any weed control surprises from last year I need to be concerned about? Did a weed species escape and set seed? The one weed that should always be considered is volunteer canola. Even the best set combine will lose at least one bushel of canola at harvesting. This works out to close to 90 to 100 canola seeds per square foot distributed back into our soils. Research has shown most of these seeds will germinate over the next two to three years. Consider, did a large percentage of these seeds germinate last fall? Will these seeds come this spring? What is the plan of attack if they do germinate before seeding? What happens if I seed early and this growth comes in crop? What type of volunteer canola am I trying to kill? How tight is the canola rotation?

3. What resistant weeds do I have? It’s important to identify these. On my farm, I have Group 1-, 2-, and 8-resistant wild oats and Group 2-resistant chickweed. Research has shown around 80 per cent of all fields within Western Canada have at least one resistant weed biotype on them. This is also the time to identify tough-to-control weeds such as Canada thistle, foxtail barley and dandelions.

4. Do I have a solid weed plan for the upcoming year? Create more than one weed plan. Have a weed control plan where you have a pre-seed option and a plan where you do not have a pre-seed option. A pre-seed option can be as simple as a cultivation, but if the weeds have not germinated yet, it will not be effective.

5. Do I want to use mature or newer chemical options? Growers should use a combination of traditional products like Group 3 and Group 8 chemistries along with newer options in Groups 13, 14 and 15. All of these chemistries have short- and longer-term residual options available.

Weed management is one of the most important factors in maximizing yield potential every year and is becoming more complex. Your crop production advisor or agronomy expert is there to help.

Gary Topham, PAg, CCA is the manager of agronomic services for Nutrien Ag Solutions in Manitoba.

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