University of Nebraska-Lincoln Extension, Institute of Agriculture and Natural Resources

May 2, 2008

Parameters for Using Preemergence Herbicides on Emerged Corn

With wet spring conditions in many parts of Nebraska, producers may be pressed to make adjustments to their intended herbicide programs. Each year questions arise on the limits of using pre-emergence herbicides on emerged corn. Table 1 lists a number of commonly used pre-mergence herbicides labeled for broadcast application after corn emergence, along with crop and weed stage or height information. This list is not comprehensive, however it does provide information on many of the commonly used products in the market place. If your herbicide choice is not listed in Table 1, be sure to check the label for use restrictions.

If the product you are using contains atrazine, the addition of a crop oil concentrate can enhance control. Atrazine is primarily translocated upward in the plant (xylem mobile). When a foliar application is made, atrazine behaves more like a contact herbicide.

If you are utilizing glyphosate-resistant corn, tank mixing glyphosate with one of the pre-emergence herbicides will improve total weed control, especially if weeds are larger than you had anticipated. If you tank mix glyphosate with a pre-emergence product in this situation, adding 17 lbs/100 gallons of AMS will improve its performance. The same will apply to tank mixing Liberty on Liberty Link corn varieties, however, you will want to use 3 lb/ac AMS (1.5 lb/ac if tank mixing with Lumax or Lexar).

Remember, applying pre-emergence herbicides with a liquid nitrogen carrier is not advised. Unacceptable crop injury will occur.

Lowell Sandell
Extension Educator, Weed Science
Mark Bernards
Extension Weeds Specialist

Table 1.  Pre-emergence herbicides that can be applied post-emergence in corn.

Herbicide

Active Ingredient(s)

Crop Stage

Weed Stage

Aatrex/Atrazine

Atrazine

0-12"

1.5"G

Bicep II Magnum/Cinch ATZ

S-metolachlor, Atrazine

0-5"

2-leafG&B

Bicep II Lite Magnum/Cinch ATZ Lite

S-metolachlor, Atrazine

0-5"

2-leafG&B

Bicep II Magnum FC

S-metolachlor, Atrazine

0-5"

2-leafG&B

Bullet

Alachlor, Atrazine

0-5"

2-leafG&B

Callisto *

Mesotrione

0-30"

0-5"B

Camix *

S-metolachlor, Mesotrione

0-12"

0-3"B

Degree

Acetochlor

0-11"

unemerged

Degree Xtra

Acetochlor, Atrazine

0-11"

2-leafG&B

Dual Magnum

S-metolachlor

0-5"

unemerged

Dual II Magnum/Cinch

S-metoloachlor

0-5"

unemerged

Dual + Atrazine

S-metolachlor, Atrazine

0-5"

2-leafG&B

Expert *, **, ***

Atrazine, S-metolachlor, Glyphosate

0-12"

weeds < 6"

FieldMaster **, ****

Acetochlor, Atrazine, Glyphosate

0-11"

weeds < 6"

Fultime

Atrazine, Acetochlor

0-11"

unemerged

G-MAX Lite

Dimethenamid, Atrazine

0-12"

1.5"G&B

Guardsman Max

Dimethenamid, Atrazine

0-12"

1.5"G&B

Harness/Confidence

Acetochlor

0-11"

unemerged

Harness Xtra/Confidence Xtra

Acetochlor, Atrazine

0-11"

2-leafG&B

Hornet WDG

Flumetsulam, Clopyralid

0-20"

2-6"G&B

Keystone/Breakfree ATZ

Acetochlor, Atrazine

0-11"

unemerged

Keystone LA/Breakfree ATZ Lite

Acetochlor, Atrazine

0-11"

unemerged

Lasso

Alachlor

0-5"

2-leafB

Lasso + Atrazine

Alachlor, Atrazine

0-5"

2-leafG&B

Lasso + Banvel

Alachlor, Dicamba

0-3"

2-leafB

Lightning (IMI corn)

Imazethapyr, Imazapyr

corn < 8 leaf

weeds < 3"G&B

Lumax/Lexar*

S-metolachlor, Atrazine, Mesotrione

0-5"

0-3"B

Marksman

Atrazine, Dicamba

0-8"

0-4"B

Me-Too-Lachlor II

Metolachlor

0-40"

2-leafB

Outlook

Dimethenamid

0-12"

unemerged

Pendimax/Prowl

Pendimethalin

0-24"

1"G

Prowl H2O

Pendimethalin

0-30"

1"G

Prowl + Atrazine

Pendimethalin, Atrazine

up to 2-leaf

up to 2-leaf

Stalwart C

Metolachlor

0-40"

2-leafG

Stalwart Xtra

Metolachlor, Atrazine

0-5"

2-leafG&B

SureStart

Acetochlor, Flumetsulam, Clopyralid

0-11"

1-2"G&B

Surpass/Breakfree

Acetochlor

0-11"

unemerged

Topnotch

Acetochlor

0-11"

unemerged

Trizmet II

Atrazine, Metolachlor

0-5"

2-leafG&B

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

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

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

**** Apply this product to Roundup Ready corn only.

G Grass

B Broadleaf

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