Agronomy Talk

Agronomy Update

Burndown Options, Planting Behind Anhydrous Ammonia and Black Cutworm

Published on Wednesday, April 12, 2017

As we prepare for planting, there are a number of things to keep in mind. From burndown to weed and pest control, there are factors to consider that will ultimately affect the season ahead.  

Winter Annual Burndown and Marestail Control

The warm fall and mild winter has left us with abundant marestail and winter annual weed populations that are taking off! As these weeds continue to grow and your herbicide applications are put on hold due to field conditions, consider the following recommendations.  

First, it’s important to remember that winter annuals are fairly easy to control. Glyphosate is still an effective herbicide for controlling weeds such as chickweed, purple deadnettle, and henbit. Marestail, on the other hand, is another animal. At this point, it’s safe to assume that glyphosate alone will NOT control marestail in your field. That being said, here are a few pre-emergent burndown options that will help you control glyphosate-resistant marestail and other winter annual weed populations in both corn and soybeans this spring.

Gramoxone® SL 2.0 at 2.5 to 3 pt.

  • Metribuzin at 4 oz.
  • Crop Oil Concentrate at 1 gal./100 gal. spray volume
  • Minimum spray volume of 15 to 20 gal./A.

Gramoxone results in very quick weed desiccation which allows soils to warm and dry out quickly. It’s also nearly half the price it has been in prior years, which makes it a very efficient and effective product for burndown purposes. For acres going to corn, substitute metribuzin with atrazine, as these products are PSII inhibitors and will increase the efficacy and enhance the herbicide activity of Gramoxone.

Liberty® at 29 to 32 oz.

  • AMS at 1.5 to 3 lb./A.
  • Minimum spray volume of 15 to 20 gal./A.

Liberty performs the best under full sunshine and with nighttime temperatures above 55°F. Target weeds less than 4 in. tall.

Sharpen® at 1 to 1.5 oz.

  • Metribuzin at 4 oz.
  • Glyphosate at 0.75 lb./A. a.e. (Example: 22 oz. Roundup® PowerMAX®)
  • MSO at 1 gal./100 gal. spray volume
  • AMS at 17 lb./100 gal. spray volume
  • Minimum spray volume of 15 gal./A.

Sharpen has a 14-day planting restriction to soybeans at 1.5 oz./A. use rate. There is no planting restriction for corn.

XtendiMax™ at 22 oz. or Engenia™ at 12.8 oz.

  • Glyphosate at 0.75 lb./A. a.e. (must be an approved tank mix glyphosate)
  • Approved water conditioning agent (NO AMS or ammonium-based additives)
  • Only for use in dicamba tolerant soybeans

2,4-D LV6 (ester formulation) at 1.33 pt.

  • Glyphosate at 1.12 lb./A. a.e. (Example: 33 oz. Roundup PowerMAX)
  • AMS at 17 lb./100 gal. spray volume
  • Relying solely on 2,4-D for marestail control

This program requires a 14-day planting restriction to soybeans. If planting corn, be sure to plant a minimum of 2 in. deep and ensure the entire seed furrow is closed.

For season-long weed control, each of these burndown programs perform best when applied in conjunction with a pre-emergent residual herbicide that aligns with the specific weed pressure you are experiencing. Remember, it’s much easier to control marestail prior to an established crop than it is post emergent.

Anhydrous Ammonia Applications and Corn?

One common question I hear this time of year is “how long do I have to wait after an anhydrous ammonia (AA) application to plant my corn?” The biggest risk in planting too soon after an AA application is if the corn seed falls within the ammonia zone or where the ammonia knife ran. To avoid seedling injury, separation in either time or space is important. Waiting three to five days before planting is usually enough time to reduce the risk of seedling injury. Under “normal” soil moisture conditions and proper application depth, there is minimal risk of seedling injury, even if planted on top of the application zone or right after AA application. However, it is important to remember that as you cross the field and drainage or soil types change, so does your application depth as well as soil moisture. That being said, waiting three to five days post application is your safest bet to ensure you don’t expose the corn seedling to injury and AA burn.

Black Cutworm

Be aware of black cutworm as it may rear its ugly head this spring for several reasons.

  • Winter annual weed pressure in many fields is extremely dense. Any field that currently has winter annuals present has the potential for black cutworm moths to lay eggs into its dense cover.
  • As cover crops have increased in popularity, so has the potential for black cutworm to be problematic. Typically cutworm moths are attracted to laying their eggs in the cover of the green vegetation.
  • Storms that come up out of the south could potentially bring black cutworm moths with them.

I will continue to provide updates on insect pressure as the season continues.

If you have further questions regarding any of the above or other agronomic concerns, please do not hesitate to contact myself or your local Beck’s representative for more information.








Gramoxone® is a registered trademark of Syngenta Group Company. Liberty® is a trademark of Bayer. Sharpen® and Engenia™ are trademarks of BASF. Roundup®, PowerMAX®, and XtendiMax™ are trademarks of Monsanto Technology.


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Luke Schulte

Luke Schulte

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