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Burning questions about burndown herbicides in corn

April 20, 2016

There are currently lots of concerns and questions around burndown applications because there are lots of variables to take into consideration: weather, weeds present, cover crops, size of the weeds, intended crop to be planted, and timing, among others. Any plant present in a corn field should be considered a weed, and it’s never a good idea to let them get out of control.

  1. What is the best option for terminating cover crops?

It is important to understand what is in the cover crop and then what is the best method. There are many good university publications on this topic. Purdue’s general guidelines can be found here with specifics about annual ryegrass here.

Despite the overwhelming desire and interest to “plant into green,” it’s better to terminate weeds before they get too big. That being said it’s also better to wait until there are more consistent daytime temperatures in the 50s for translocated products to work. Gramoxone® SL 2.0 herbicide works better than glyphosate under cooler conditions. Best practices for Gramoxone SL 2.0 can be found here.

  1. Can residual herbicides and burndowns be sprayed together?

A lot of factors go into this, especially planting timing. The earlier the residual application is made, the amount of days of residual left after planting may be decreased. When there is a cover crop or large amount of weeds present, it’s always a good idea to apply the burndown early with 2,4-D or Sharpen® herbicide and come back with residual herbicides close to or right after planting. When applications are combined later, soil and herbicide contact is compromised and small germinating weeds like marestail may not get covered under the taller weeds and cover crops.

  1. Should you add anything to Acuron®, Lexar® EZ, or Lumax® EZ herbicides in your no-till burndown?

These products are labeled on a number of winter annual and early emerging annual broadleaves. However it is recommended to add glyphosate or Gramoxone SL 2.0 to applications specifically when grass is present and weeds are greater than 3”.  Specific technical recommendations can be found below:

These weed management options can help reduce the weed seed bank, maximize herbicide diversity and ultimately help grow more corn.

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