Delayed PRE herbicide applications in corn
by Micheal D. K. Owen
blueline.jpg (1822 bytes)May 9 2008 -  Given the way the season has developed, the best intentions to apply an Early Preplant (EPP) herbicide application prior to corn planting has gone out the window and it appears that applying a preemergence (PRE) application immediately after planting is also becoming a slim chance.  Thus, many who intend to use a soil-applied residual herbicide treatment in corn may be forced to make the application early postemergence (EPOST) to the weeds and possibly the corn.  Below is a table containing herbicide options available in corn modified from an article that appeared in the University of Nebraska CropWatch newsletter (http://cropwatch.unl.edu).  The list likely does not include all options given the generic status of a number of these herbicide active ingredients.

 The concern about the delayed PRE/EPOST herbicide treatment, regardless of whether or not residual products are included, is making the application soon enough to protect crop yield.  It is typical that herbicides will kill weeds that are larger but often after potential yield has been lost.  Furthermore, some weeds (i.e. winter annuals) become extremely difficult to control as they grow larger and the potential for crop injury also increases as the crop gets larger.  Thus, the best option is to make the residual herbicide application immediately after planting.  If this is no longer an option, apply the treatment as soon as possible after planting.

 Please recognize that some herbicides are registered for application EPOST to the crop but do not have POST activity on weeds.  Also, many of these products can be applied to corn that is considerably larger than appropriate to protect the potential yield and weed control may be variable due to the uneven distribution of the spray on the weeds (the corn canopy interferes with the spray coverage).  Be sure to follow the label directions and understand the limitations of applications as the weeds and corn get larger.  Also, it is highly unlikely that any of the EPOST treatments will meet expectations as a “season long, one pass treatment”.  Scout the fields prior to application and use the correct product to control the weeds that are present.  Recognize that some of the labels are not clear about the size of weeds that may be controlled after they emerge. 

 

Herbicide

Active Ingredient(s)

Crop Stage

Weed Stage
 

Aatrex/Atrazine

Atrazine

0-12"

1.5"
 

Bicep II Magnum/Cinch ATZ

S-metolachlor, Atrazine

0-5"

2-leaf
 

Bicep II Lite Magnum/Cinch ATZ Lite

S-metolachlor, Atrazine

0-5"

2-leaf
 

Bicep II Magnum FC

S-metolachlor, Atrazine

0-5"

2-leaf
 

Bullet

Alachlor, Atrazine

0-5"

2-leaf
 

Callisto 1

Mesotrione

0-30"

0-5"
 

Camix 1

S-metolachlor, Mesotrione

0-12"

0-3”
 

Degree

Acetochlor

0-11"

Prior to emergence
 

Degree Xtra

Acetochlor, Atrazine

0-11"

~2-leaf
 

Dual Magnum

S-metolachlor

0-5"

Prior to emergence
 

Dual II Magnum/Cinch

S-metolachlor

0-5"

Prior to emergence
 

Dual + Atrazine

S-metolachlor, Atrazine

0-5"

2-leaf
 

Expert 1,2,3

Atrazine, S-metolachlor, Glyphosate

0-12"

weeds < 6"
 

FieldMaster 2,4

Acetochlor, Atrazine, Glyphosate

0-11"

weeds < 6"
 

Fultime

Atrazine, Acetochlor

0-11"

~2-leaf
 

G-MAX Lite

Dimethenamid, Atrazine

0-12"

1.5"
 

Guardsman Max

Dimethenamid, Atrazine

0-12"

1.5"
 

Harness/Confidence

Acetochlor

0-11"

Prior to emergence
 

Harness Xtra/Confidence Xtra

Acetochlor, Atrazine

0-11"

2-leaf
 

Hornet WDG

Flumetsulam, Clopyralid

0-20"

2-6"
 

Keystone/Breakfree ATZ

Acetochlor, Atrazine

0-11"

Prior to emergence
 

Keystone LA/Breakfree ATZ Lite

Acetochlor, Atrazine

0-11"

Prior to emergence
 

Lightning (IMI corn)

Imazethapyr, Imazapyr

corn < 8 leaf

weeds < 3"
 

Lumax/Lexar*

S-metolachlor, Atrazine, Mesotrione

0-5"

0-3"
 

Marksman

Atrazine, Dicamba

0-8"

0-4"
 

Me-Too-Lachlor II

Metolachlor

0-40"

2-leaf
 

Outlook

Dimethenamid

0-12"

Prior to emergence
 

Pendimax/Prowl

Pendimethalin

0-24"

Prior to emergence
 

Prowl H2O

Pendimethalin

0-30"

Prior to emergence
 

Prowl + Atrazine

Pendimethalin, Atrazine

up to 2-leaf

up to 2-leaf
 

Stalwart C

Metolachlor

0-40"

2-leaf

 

Stalwart Xtra

Metolachlor, Atrazine

0-5"

2-leaf
 

SureStart

Acetochlor, Flumetsulam, Clopyralid

0-11"

1-2"
 

Surpass/Breakfree

Acetochlor

0-11"

Prior to emergence
 

Topnotch

Acetochlor

0-11"

Prior to emergence
 

Trizmet II

Atrazine, Metolachlor

0-5"

2-leaf

1Severe injury may occur if Callisto is applied postemergence to corn that has been treated with Counter or Lorsban.  Do not tank mix with any organophosphate or carbamate insecticide.  Do not cultivate within seven days of application.

2Do not tank mix this product with any other herbicide when applied postemergence.

3Do not mix this product with complex fertilizer mixtures such as 10-34-0 or flowables.  Use only water or liquid nitrogen carrier.

4Apply this product to Roundup ReadyTM corn only.

 

 Prepared by Micheal D. K. Owen, extension weed management specialist, Department of Agronomy, Iowa State University

For more information contact:
ISU Extension Agronomy
2104 Agronomy Hall
Ames, Iowa 50011-1010
Voice: (515) 294-1923
Fax: (515) 294-9985
http://www.weeds.iastate.edu		 Submit questions or comments here.  

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Common chemical and trade names are used in this publication. The use of trade names is for clarity by the reader. Inclusion of a trade name does not imply endorsement of that particular brand of herbicide and exclusion does not imply nonapproval.