Follow these '10 Commandments' of weed control for 2021

Thou shalt not let problem weeds compromise profitability.

Syngenta, university researcher advocate holistic approach to maximize yield potential and minimize future obstacles.

The “10 Commandments” of weed management provide a comprehensive framework for planning

Maximum income for minimal investment. That’s the goal for every farmer, every year. The challenge of weed control compromises that goal – especially as herbicide-resistant weeds gain ground. 

Stevan Knezevic, weed management specialist at the University of Nebraska, offers “10 Commandments” of weed management that growers can reference to make sure all their bases are covered this coming season. Knezevic and Mark Kitt, corn herbicide technical product lead for Syngenta, weigh in on weed management for corn growers. 

  • Commandment 1: Know your weeds and understand their life cycles and biologies. This is the foundation for all of the commandments. “A full understanding of the weeds in your region and how they may interact with your crops is an important step in managing an efficient and successful operation,” Knezevic says. 
  • Commandment 2: Rotate your crops. “Crop rotation is a key component in an effective weed resistance management strategy,” Kitt adds. “It will extend the range of available herbicides and agronomic practices.”
  • Commandment 3: Rotate your herbicide sites of action. “By having extra sites of action, you are widening the spectrum of weed control,” Knezevic says.
  • Commandment 4: Use premixes with multiple effective sites of action. Emphasis on “effective.” Products that contain modes of action already resistant to target weeds aren’t necessarily effective, and farmers who use them are essentially going to battle with less ammunition. 
  • Commandment 5: Use full labeled rates of herbicides. “Full label rates will provide a full length of residual activity that should cover the critical period of weed control,” Knezevic says. “By reducing the label rate, you’re in danger of not killing the weed, but only crippling it. A surviving weed that is growing after a herbicide application has a chance to potentially produce herbicide-resistant offspring.”
  • Commandment 6: Scout your fields. “Go out and scout those fields,” says Knezevic. “Look for survivors, and look for regrowth because that regrowth can most likely carry a resistance gene, so you will have problems next year.”
  • Commandment 7: Apply postemergent applications, ideally before new weed growth is discovered. Overlapping residuals can help prevent these weed escapes. 
  • Commandment 8: Use cultural practices to manage weeds, and don’t overlook your field borders. “This is where employing sound agronomic practices will prove to be especially beneficial, including tillage and crop rotation,” Knezevic says. “Any uncontrolled weeds will produce seeds. If you don’t control them well and let them drop seeds, you’re going to fight them for at least three to five more years into the future.”
  • Commandment 9: Use clean equipment, especially during harvest, to manage weed seed. “Over the last 10 years or so, we have seen a rapid spread of glyphosate-resistant waterhemp and Palmer amaranth, which were not spread by weeds, animals, or wind. They were spread by combines during harvest,” Knezevic warns.
  • Commandment 10: Know the cost of poor weed management. “The culmination of the commandments is that in managing cost vs. yield, understand that it is much more expensive if you spend less money and do not kill the weeds,” Knezevic says. “A general rule of thumb is that for every stage of delayed weed control, there is a 2% loss of potential yield.”
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