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Jun
4
Posted by:
WCM Staff
6/4/2009 12:14 PM
In driving through the state this last week, most corn fields look like they have a preemergence program that has controlled early season weeds well. However, there are some corn fields with modest densities of weeds emerging. These fields will soon reach the time when postemergence herbicides need to be applied to protect corn yields. Time for Postemergence Corn Herbicides
Chris Boerboom, Extension Weed Scientist
In driving through the state this last week, most corn fields look like they have a preemergence program that has controlled early season weeds well. However, there are some corn fields with modest densities of weeds emerging. These fields will soon reach the time when postemergence herbicides need to be applied to protect corn yields. In terms of yield protection, remember that it is better to err on the early side when it comes to weed control. It may be tempting to delay an herbicide application until all the weeds are up so they can all be killed. Unfortunately, they will have competed with corn for too long and have cut into yield by this time. An early herbicide application before weeds are 4 inches tall or the corn is about at the V3 stage will remove weeds before they inflict much damage. Even though some weeds might emerge after this timing (if a non-residual herbicide was used), the yield loss from their competition for the whole rest of the season will be far less than allowing early weeds to compete.
If later herbicide applications need to be made to control problem weeds or in rescue situations, be sure to make the applications before the maximum labeled growth stages to avoid corn injury or illegal residues in the harvested corn.
Common corn herbicides that can be applied postemergence and their labeled growth stages.
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Herbicide
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Corn stage
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Accent
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0-20" or V6; to 36" or V10 with drop nozzles
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Atrazine
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0-12"
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Basagran
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no restriction
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Basis
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0-V2
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Beacon
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4-20" or V6; to tasseling with drop nozzles
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Buctril
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4 leaf to before tasseling
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Cadet
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V2 to 48”
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Callisto
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0-30" or V8
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Celebrity Plus
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4-24" or V6
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Dicamba (Clarity, etc.)
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0-8" or 5 leaf; to 36" with drop nozzles
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Glyphosate (Roundup, etc.)
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0-30" or V8; to 48” with drop nozzles on RR2 hybrids
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Halex GT
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0-30” or V8
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Hornet WDG
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0-20” or V6; 20-36" with drop nozzles if harvested for grain
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Impact
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emergence to 45 days before harvest
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Laudis
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0-V8
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Ignite
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0-24" or V7; 24-36" with drop nozzles
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Marksman
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0-8" or 5 leaf
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NorthStar
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4-20" or V2 -V6; to 36" with drop nozzles
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Option
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V1-V6; to V7 with drop nozzles
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Permit
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0-36"
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Priority
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0-V8
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Resolve Q
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0-V6 or 20”
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Shotgun
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0-8"; to 12" with drop nozzles
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Status
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4-36” or V2 to V10
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Steadfast
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0-20" or V6
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Stinger
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0-24"
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Stout
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0-16” or V5
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Unity
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V1-V5 or 16”
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Yukon
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0-36"
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2,4-D
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0-8"; to before tasseling with drop nozzles
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Herbicides listed below can be applied postemergence for soil residual herbicide activity. They do not provide postemergence control of grass weeds.
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Bicep Lite II Magnum
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0-5”
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Camix
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0-30" or V8
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Dual II Magnum
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0-40"
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G-Max Lite
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0-12"
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Harness, Surpass, etc.
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0-11"
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Harness Xtra, Keystone LA
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0-11”
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Lumax
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0-12"
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Outlook
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0-12"
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Prowl
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0-30" or V8
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SureStart
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0-11”
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In the chart, “V” refers to “V-stage”, which describes the number of leaf collars on a corn plant. The leaf collar is region where the leaf blade joins the leaf sheath, which wraps around the stalk.
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