With respect to burndown before corn planting it is getting late early!  There has been very little burndown applied to date and this week looks to be a wash.  The likelihood of getting more than just a handful of days to apply burndown before the end of the month is not good.  Fortunately, we can apply atrazine in with the burndown. Gramoxone Inteon or glyphosate tankmixed with atrazine can provide a very effective burndown of even large existing weeds. 

Positives

1. A new herbicide premix from Bayer that consists of Laudis (similar herbicide to Callisto) and an ALS-inhibitor thiencarbazone.
2. In our research it has provided good post emergence control of most broadleaf and grass weeds.
3. It will provide good glyphosate-resistant horseweed and Palmer control.

Management Considerations

1. Can be applied up to V6 corn.
2. Tankmix atrazine in with Capreno to provide better control of large seeded broadleaf weeds. 

Halex GT (Dual II Magnum + Callisto + Glyphosate) Rate: 3.6 to 4 pts/A

Positives

1. Was the most commonly used premix used in Tennessee in 2010. 
2. Provides good all around weed control including horseweed control.
3. Most economical way to purchase Callisto.

Management Considerations

1. 3.6 pts/A rate provides 3 oz/A of Callisto.
2. Can be applied up to V8 or 30” tall corn.
3. Do not tankmix any foliar fertilizer or fungicide with a Halex GT application. 

Bicep (Dual II Magnum + Atrazine) Rate: 1.6 to 2.6 qts/A

Positives

1. Has been used on more corn acres then any other corn premix. 
2. Provides good all around weed control with good crop safety.

Management Considerations

1. 2 qts/A rate provides 1.55 lbs ai of atrazine.
2. The herbicide Expert is essentially Bicep premixed with glyphosate.

Harness Xtra 5.6, Degree Xtra, Breakfree ATZ (Acetochlor + Atrazine) Rate: 1.7 to 3 qts/A for Harness Xtra or 2.9-3.7 for Degree Xtra or 2.2 to 3 qts/A for Breakfree ATZ.

Positives

1. The non-encapsulated acetochlor formulations Harness and Breakfree have provided comparable pigweed and grass control to Dual II Magnum. 
2. Degree Xtra is an encapsulated formulation that releases slowly over time.  Limited research has shown about a week longer residual control of pigweeds than other acetochlor formulations.

Management Considerations

1. 2.1 qts/A rate of Harness Xtra provides 1.3 lbs ai of atrazine or 3.5 qts/A of Degree Xtra provides 1.17 lbs ai of atrazine or 2.5 qts/A of Breakfree provides 1.4 lbs ai of atrazine.

Lexar (Dual II Magnum + Callisto + Atrazine) Rate: 3 qts/A

Positives

1. Very good resistance management product with three modes of action for control of many broadleaf weeds.
2. Callisto can provide good glyphosate-resistant horseweed control.
3. 3qts/A of Lexar will provide 5.4 ozs/A of Callisto and is the most economical way to buy Callisto.

Management Considerations

1. 3 qts/A rate of Lexar provides 1.31 lbs ai of atrazine.

Regardless of whether the corn being managed is Roundup Ready or not, the best overall weed control will most often be achieved with some kind of two pass program.  One reason this works best is due to being able to apply more atrazine in two passes (2.5 lbs/A) compared to all in one application (2 lbs/A). A good approach is to either use Gramoxone Inteon or glyphosate mixed with 16 to 32 ozs/A of atrazine for burndown.  Then follow early post emergence (up to 12” corn) with glyphosate plus atrazine or even better with one of the premixes mentioned above.  Many folks do not realize that herbicides like Dual II Magnum, Harness, etc. can be applied post emergence to corn.  They can and I often recommend this method as those residuals are there when most needed.  The new product Capreno and the very popular Halex GT are really designed to use as the second application in a two pass program.  Because they do not contain atrazine they can be applied later than 12” corn.