Don't Forget the Burndown in No-till
Chris Boerboom, Ext. Weed Scientist
The recent warm weather and rain is bringing a good crop of winter annual weeds to life and early summer annual weeds will be right behind. In no-till fields, it is important to apply an effective burndown treatment to control these weeds at planting, even if the crop being planted is Roundup Ready. Studies have shown that Adelayed burndown@ treatments (eg. waiting until the crop has emerged) are often not adequate to remove the damage caused by these early season weeds. Field observations of the problems caused by delayed burndown applications should convince most people this is not the best practice, especially with some weeds like giant ragweed.
There are several effective burndown herbicide programs that can be used before corn or soybeans and I have made a few summary comments below.
Corn burndown options
Glyphosate - 0.38 to 0.75 lb ae/a depending on weed species and size
Glyphosate may be the burndown treatment of choice, but it lacks residual activity. Consider if a tank mix with a residual herbicide will provide the necessary control or improve flexibility if postemergence herbicides are planned. See the horseweed article for additional comments that justify the addition of 2,4-D as a glyphosate-resistance management practice.
Gramoxone Inteon - 2 to 4 pt/a depending on weed size
Gramoxone is effective on annual weeds, but may only burn the top growth off perennials and has no residual activity. Tank mix partners that include atrazine will increase burndown activity because triazines synergize Gramoxone. Plus, the atrazine then provides residual activity. Gramoxone is a contract herbicide so good spray coverage is important.
2,4-D ester - 1 pt/a
2,4-D is often a good tank mix partner in many burndown treatments to increase broadleaf weed control. Adding 2,4-D to glyphosate generally improves dandelion control. There is some risk of injury to shallow planted corn if applied close to planting. Some labels recommend that applications are made 7 days before planting.
Basis - 0.33 to 1 oz/a
Basis is a premix of Resolve and Harmony GT. It provides burndown and some early residual control of many annual grass and broadleaf weeds, especially when tank mixed with atrazine + 2,4-D
Resolve - 0.75 to 1 oz/a
Resolve provides burndown of several (small) annual grasses and broadleaf weeds. The addition of atrazine or glyphosate will improve control of several common broadleaf weeds. It will provide early season residual control on foxtails and several broadleaf weeds. If comparing the residual of Basis and Resolve, 1 oz of Resolve contains half as much rimsulfuron as 1 oz of Basis.
Distinct - 2 to 6 oz/a
Distinct is labeled for preplant applications and may be useful when tank mixed with glyphosate to kill old hay fields.
Field Master - 3.5 to 4 qt/a
Field Master is a premix of glyphosate, Harness, and atrazine that provides burndown from the glyphosate and residual. However, the atrazine rate is generally too high for Wisconsin.
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Field Master =
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glyphosate +
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atrazine +
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Harness
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2 qt
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0.28 lb ae
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0.75 lb
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1.1 pt
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2.6 qt
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0.36 lb ae
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1.0 lb
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1.5 pt
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4 qt
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0.56 lb ae
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1.5 lb
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2.3 pt
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Soybean burndown options
Glyphosate - same comments as above.
Gramoxone Inteon - same comments as above except Sencor or Lorox can be tank mixed to synergize the Gramoxone and provide residual activity.
2,4-D ester - same comments as above except there is a minimum 7 day interval between spraying and planting soybeans.
Extreme - 3 pt/a
Extreme is a premix that provides the equivalent of 4 fl oz/a of Pursuit and 0.56 lb ae/a of glyphosate at a discounted price. This is a good combination of burndown activity with fair to good residual on several grasses and good residual on several broadleaf weeds.
Sequence - 2.5 to 4 pt/a
Sequence is a premix of Dual II Magnum and glyphosate so it provides burndown and residual grass control. The 2.5 pt/a rate provides 0.7 lb ae/a of glyphosate and should be adequate in most burndown situations. This rate also provides 1 pt/a of Dual II Magnum, which gives good early season grass residual.
Canopy is now labeled for southern Wisconsin (south of I-90 west of Madison and south of I-94 east of Madison), but only at the lowest rate. At 2.25 oz/a, Canopy provides the equivalent of 1.9 oz/a of Sencor and 1 oz/a of Classic. Canopy can be tank mixed with glyphosate to improve burndown of broadleaf weeds like dandelion and add some residual control.