Weed Control Lessons for Local Farmers

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Article by Chris Snip
Crop Sales Specialist
AGRIS Co-operative, COTTAM

In 2019, I shared insights on weed control that are still relevant today, especially after another challenging spring. These lessons remain critical for effective weed management, and are worth revisiting.

1. Timing of Burndown Applications: Applying a burndown herbicide at the first opportunity doesn’t necessarily mean it’s early. A burndown in mid-June requires a different approach than one applied on May 1st. The timing impacts the weed growth stage and the herbicide’s effectiveness.
2. Weed Size Matters: Knee-high weeds may seem small compared to waist-high ones, but they are still beyond the optimal size for most herbicide labels. Expect less-than-perfect control when dealing with larger weeds.
3. Glyphosate Resistance is Everywhere: Every field in Southwestern Ontario has some level of glyphosate-resistant weeds. While some fields may have lower populations or different species, resistance is widespread.
4. Spring Herbicide Pass is Crucial: Your first herbicide application in the spring is your best chance to control weeds effectively. Make it count.
5. Fall Burndown is Worth It: A fall burndown is invaluable and worth every penny. It sets the stage for better weed control in the spring.
6. Rainfast Times Matter: When the label says two or four hours for rainfast, it means exactly that—and sometimes more. Glyphosate has spoiled us in recent years, as it often works if applied before rain. However, this doesn’t hold true for dicamba or Enlist, where rain events just three to four hours after application can lead to poor control.
7. Use the Highest Label Rates for Larger Weeds: If the label recommends higher rates for larger weeds, follow it. And if surfactants are suggested for better control, don’t skip them.
8. Water Volumes are Important: Some herbicides require higher water volumes for effective coverage. While cutting rates might work on smaller weeds, larger ones need more water to ensure proper control.
9. Multiple Modes of Action: Using tank mixes with multiple modes of action provides superior control of hard-to-kill weeds. In contrast, products that antagonize each other can reduce effectiveness. The more modes of action in your program, the less regrowth you’ll see in tough-to-control weeds.
10. Learn from Your Successes and Failures: If most of your fields have good weed control despite difficult conditions, be thankful. Reflect on what worked well and what didn’t, and use those lessons moving forward.
    

Herbicide-resistant weeds are here to stay. The best we can do is learn how to manage them effectively, regardless of the challenges Mother Nature throws our way.