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Weed Management is a Strategy and not a Tactical Activity (09/23/21)

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Congratulations for navigating a challenging field season. It is the harvest season which is agricultures’ version of ‘erasing the board’ or ‘cleaning the slate.’ Stated differently, we erase the memory of spatial weed control challenges in fields when we harvest grain and clear the field for the next cropping season.

I remember when controlling weeds was a tactical activity. We observed weeds and timed their control with appropriate weather conditions. We assumed application would result in complete weed control if we followed label instruction and ensured weed sizes were correct at application. Well, as Bob Dylan once stated, ‘the times they are a-changin.' Weed resistance, unfortunately, has changed everything.

Harvest time is note-taking time and a continuation of our weed management strategy. Collect notes at harvest including documenting the most important and second most important weeds in fields and draw spatial maps document where weeds are most severe. Check your record keeping to ensure herbicides used in 2021 was documented. You can add details such as Site of Action (SOA) grouping over the winter. As one prepares for 2022, consider herbicide options ensuring rotation flexibility, and above all, ensuring diverse SOA groupings for your next crop and for future crops.

I talk a lot about an integrated weed management plan for weed control. An integrated weed management plan is the most important component of weed control and it includes multiple levels. It begins by combining mechanical, chemical, and cultural control options. If you are like me, your weed management plan probably is heavily weighted to herbicides. I try to incorporate tillage into my programs by ensuring no emerged weeds at planting. I also am a believer in inter-row cultivation. However, the foundation of my weed control programs are herbicides. Next, I structure my programs to have at least two effective herbicides soil-applied and postemergence for control against my most important weeds in fields. Finally, and most important of all, I use the crop rotation to extend the integrated weed management plan into the next season, introducing unique herbicides from different SOA groups, especially against troublesome weeds like pigweed. What crop provides the best opportunity to nail your most troublesome weed? Seize that moment but don’t let up; maintain weed control across the cropping sequence.

There was a time when weed control was a series of discrete operations that started and ended with each cropping season. Not anymore. Weed management must be a series of premeditated plans providing continuous control extending across the crop sequence. And don’t hesitate to change it up. As Stephen Powles, professor at the University of Western Australia stated, if your weed management plan is working then change it as you will want to ensure diversity in your programs and to protect against weed resistance.

 

Tom Peters

Extension Sugarbeet Agronomist

NDSU & U of MN