Weed control challenges for sugar beets in 2008

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.      

After a long wait, Michigan sugar beet growers will be growing Roundup Ready sugar beets for the first time this year. For most of us, the use of glyphosate (Roundup) in Roundup Ready sugar beets should make weed control simpler and more consistent. However, as with any change in production practices there will be a learning curve to using this technology. Additionally, there will be other challenges because most growers will also still have conventional sugar beets acres for which timely weed control will be important.

Precautions need to be taken when growing both Roundup Ready and conventional sugar beets

  • Keep good records of which fields are planted to the different sugar beet varieties. Because most growers will likely have both Roundup Ready and conventional sugar beet varieties on their farms this year, fields should be clearly marked so there are no mistakes in herbicide applications. There can’t be a worse feeling than spraying glyphosate (Roundup) on a field that does not contain the Roundup Ready trait. This occurrence was common when Roundup Ready soybean, corn, and cotton were first commercialized. One small mistake can cost several thousands of dollars, so it is important to check, double check and triple check that you are in the correct field before spraying glyphosate.
  • Make sure the sprayer is properly cleaned outwhen switching from spraying glyphosate in Roundup Ready sugar beets to conventional herbicides (micro-rates or standard splits) in non-Roundup Ready sugar beets. Without proper cleanout, glyphosate solutions or residues left in the tank will lead to tank-contamination that can cause death to sugar beets in non-Roundup Ready (conventional) sugar beet fields.
  • Be timelywith herbicide applications. One of the biggest differences in conventional weed control programs compared with Roundup Ready weed control systems is that conventional herbicides generally need to be sprayed when the weeds are less than 0.5-inch tall and glyphosate in Roundup Ready sugar beets can be applied when weeds are much larger. Keeping track of weed sizes by scouting both Roundup Ready and conventional sugar beet fields is extremely important.

Current recommendations in Roundup Ready sugar beets

  • Plant Roundup Ready sugar beets in a weed-free seedbed.
  • The first glyphosate application should be made when weeds are 2-inches tall. Subsequent applications should be made before additional weed flushes exceed 4-inches tall. Two to four applications will be needed for season-long weed control.
  • Glyphosate should be applied at a minimum rate of 0.75 lb ae/A (i.e., 22 fl oz/A Roundup WeatherMax or Roundup PowerMax). Higher rates up to 1.1 lb ae/A (32 fl oz/A Roundup WeatherMax or PowerMax) can be applied to harder-to-control weeds prior to 8-leaf sugar beet.
  • Ammonium sulfate (AMS) at 17 lb/100 gal should always be added to maximize glyphosate performance.
  • Maximum in crop glyphosate application rates include two applications prior to 8-leaf sugar beets totaling 1.9 lb ae/A and two applications after the 8-leaf stage until 30 days prior to harvest totaling 1.5 lb ae/A.
  • Dual Magnum or Outlook can be tank-mixed with later glyphosate applications to provide residual control of late-emerging grasses and pigweed. Sugar beets should have at least 4-true leaves.

Roundup Ready sugar beets will be an excellent weed control asset to Michigan sugar beet growers. But as we make this transition, keep several of these precautions in mind. It will also be important for growers to be good stewards of the Roundup Ready technology, so its benefits will be sustainable in the future.

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