In southeast Indiana we are recommending that producers do not plant no-till soybeans into fields with live horseweed plants. Control the horseweed before planting with 2,4-D, 2,4-D + Classic, Canopy or glyphosate, or Gramoxone + Sencor + 2,4-D. We are recommending that all burndown applications in southeast Indiana contain 1 to 2 pts/A of 2,4-D. As horseweed size increases to 8 in or greater the higher rate of 2,4-D is recommended. Producers will need to have this application made one month to two weeks prior to their targeted planting date or reduce rates to 1 pt/A, which has to be applied at least 7 days prior to planting (check each formulation label for specific plant-back restrictions).

In southeast Indiana , horseweed will continue to emerge well into the summer. Several herbicides can be used at planting to provide residual control of horseweed and include FirstRate, Classic, Sencor, Python, Valor, and Authority. For postemergence control, the addition of FirstRate or Classic to glyphosate will really be the only effective on a widespread basis if the population is not resistant to ALS inhibitors. This points out the importance of getting this weed controlled before planting! Other management practices should include rotating continuous soybean fields out of soybean production for at least one year.

Additional management studies in corn and soybean are currently underway. Preliminary results will be posted soon.

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For more information regarding this web page please contact Vince Davis, Bill Johnson, or Glenn Nice.