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post-emerge-corn-herbicides.jpg University of Nebraska-Lincoln
Corn at the two to three leaf stage in a field near Carleton, NE. Many residual herbicides can be applied after corn emergence. See Table 1 for more details.

Which residual herbicides to use on emerged corn?

Consider growth stage, weed height and tank-mixes when applying post-emerge herbicide on corn.

Application of soil residual herbicides is important because they deliver a few weeks of residual weed control and aid in weed resistance management by incorporating additional site(s) of action in herbicide program. Several residual herbicides can be applied after corn emergence without injury to corn. A Few important factors should be considered when addressing weed control with residual herbicides applied after corn emergence:

  • Corn growth stage
  • Weed height
  • Tank-mix partner

Except some premix products such as Acuron, Harness Max, and Resicore with multiple herbicide active ingredients, these products generally do not have foliar activity and will not control weeds present at the time of application. Therefore, they should be tank-mixed with foliar active herbicides labeled in corn for control of existing weeds. Some of the herbicides, including Acuron, Anthem Maxx, Bicep II Magnum, Breakfree ATZ Lite, Degree Xtra, FulTime NXT, Keystone LA NXT, and Volley ATZ NXT contain active ingredients (such as atrazine) that has foliar activity. When applied at the correct weed growth stage, they will provide burndown activity (Table 1). Growers should consult product labels for additional information, such as the need for tank-mix partners or spray additives to improve control of existing weeds. For example, the post-emergence activity of atrazine can be increased by including an oil additive, yet additives should not be used if applying Balance Flexx or Corvus after corn emergence (Table 1).

Tank-mix partners may cause other effects regardless of the application timing. Follow application timing and other restrictions of tank-mix herbicide partner(s) as noted in the herbicide label. Table 1 has specific information for residual herbicides that can be applied after corn emergence with regard to corn stage and weed height. Length and effectiveness of residual activity from in-crop herbicide application will vary depending on:

  • Weed species present
  • Application rate of herbicide
  • Rainfall or irrigation following application (minimum of 0.5 inch within a week of application is ideal to activate residual herbicide)
  • Density of the weed and crop canopy at the time of application
  • Length of subsequent weed germination events

 

Table 1. Corn growth stage and maximum weed stage when residual herbicides can be applied post-emergence.

Herbicide

Corn Stage

Maximum Weed Stage

Aatrex / Atrazine

0-12”

1.5”

Acuron

0-12”

3”

Anthem MAXX

V4

2”

Armezon PRO

0-30” Or V8

4”

Balance Flexxa

V2

1.5”

Bicep II Magnum / Cinch ATZ

0-12”

2-leaf

Bicep II Lite Magnum / Cinch ATZ Lite

0-12”

2-leaf

Bicep II Magnum

0-12”

2-leaf

Breakfree

0-11”

unemerged

Breakfree ATZ

0-11”

unemerged

Breakfree ATZ Lite

0-11”

unemerged

Callistob

0-30”

4”

Corvusa

V2

1.5”

Degree

0-11”

unemerged

Degree Xtra

0-11”

2-leaf

Dual Magnum

0-5”

unemerged

Dual II Magnum / Cinch

0-40”

unemerged

Expert

0-12”

6”

FulTime NXT

0-11”

unemerged

G-MAX Lite

0-12”

1.5”

Guardsman Max

0-12”

1.5”

Harness Maxx

0-11”

3”

Harness Xtra / Confidence Xtra

0-11”

2-leaf

Hornet WDG

0-20”

7”

Instigate

V2

3”

Keystone

0-11”

unemerged

Keystone LA NXT

0-11”

unemerged

Lumax EZ / Lexar EZ

0-12”

3”

Outlook

0-12”

unemerged

Prowl H2O

0-30”

1”

Python

0-20”

6”

Resicore

0.12”

2”

Resolve

0-12”

3”

Surpass NXT

0-11”

unemerged

Stalwart C

0-40”

2-leaf

Stalwart Xtra

0-5”

2-leaf

SureStart / TripleFLEX

0-11”

2” broadleaves

TopNotch

0-11”

unemerged

Warrant

0-30”

unemerged

Zemax

30” or V8

5”

Zidua

V4

unemerged

a If Balance Flexx and Corvus is applied after the corn has emerged; do not add crop oil concentrate.
b Injury may occur if Callisto is applied post-emergence to corn that has been treated with Counter. Do not tank-mix Callisto with any organophosphate or carbamate insecticide. Do not cultivate within seven days of application.

Originally posted by University of Nebraska-Lincoln.

TAGS: Weeds
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