Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
A lot of the early planted corn needs to be scouted to determine if you are having weed emergence. The corn throughout the state is growing slowly and is nowhere near the stage it typically is in late May. So there will be a number of considerations for postemergence herbicide applications. In general, early emerging weeds are a bigger issue than late emerging weeds because they cause more yield loss, tend to get taller and larger, which causes more problems at harvest, and they produce more seeds. The following table was developed to help making these decisions. If tankmixing herbicides, follow the most restrictive label. The addition of atrazine will improve performance of many of the following herbicides (in particular Callisto, Halex GT, Laudis, Capreno, Impact, or Armezon).
This table is only for comparison of selected herbicides, be sure to read and follow all labels.
| Herbicide | Constituent Products | Broadcast Application/ Drop nozzles |
Comments |
| 2,4D | <8 inches tall /
Drop nozzles up to 36” |
Some 2,4D formulations allow application up to tasseling.
Limited to no residual control |
|
| Accent Q | 20 inches tall (freestanding) or <6 collars (V6 stage) /
Drop nozzles up to 36” or V10 stage |
Limited to no residual control | |
| Aim | Up to 8leaf collar stage (V8) /
Drop nozzles up to V14 stage |
Excellent for velvetleaf, but other species must be small for effective control.
No residual control |
|
| Atrazine | 12 inches tall | Residual control depends on rate – generally fair to good residual control | |
| Banvel or Clarity | dicamba | 1 pt: 8 inches tall or 5 leaves
0.5 pt: 8–36 inches tall or 15 days before tassel emergence |
Do not apply Banvel or Clarity near soybeans if corn is >24 inches tall, or if soybeans are >10 inches tall or have begun to bloom.
Limited to no residual control |
| Cadet | Up to 48 inches tall /
Drop nozzles are permitted before tasseling |
Excellent for velvetleaf, but other species must be small for effective control.
No residual control |
|
| Callisto,
Callisto GT |
Callisto + glyphosate |
Up to 30 inches tall (or 8-corn leaf stage) | Improved control with the addition of atrazine.
Residual control depends on rate – generally fair to good residual control |
| Capreno | Laudis + thiencarbazone | Up to V6 (6 collars)
Drop nozzles up to V7 stage |
Improved control with the addition of atrazine.
Limited residual control |
| DiFlexx | dicamba + safener | Up to 36 inches tall (V6 stage) /
Drop nozzles up to V10 stage |
Limited to no residual control |
| Glyphosate products | Up to 30 inches tall (V8 stage) | Apply to Roundup Ready hybrids only
No residual control |
|
| Halex GT | Dual + Callisto + glyphosate | Emergence to 30 inches tall (8leaf stage) | Improved control with the addition of atrazine.
Residual control depends on rate – generally good residual control |
| Impact or Armezon | Up to 45 days prior to corn harvest /
Drop nozzles are permitted |
Improved control with the addition of atrazine.
Limited residual control |
|
| Laudis | Emergence up to V8 stage | Improved control with the addition of atrazine.
Limited residual control |
|
| Liberty 280 | Emergence to V5 (5 developed collars)
Up to 36” tall |
Apply to Liberty Link or GR corn hybrids only.
No residual control |
|
| Realm Q | Resolve + Callisto | Up to 20 inches tall but with no more than 6 collars | Residual control depends on rate – generally fair to good residual control |
| Roundup products | Up to 30 inches tall (V8 stage) | Apply to Roundup Ready hybrids only
No residual control |
|
| Status | dicamba + difluenzapyr + safener | 4–36 inches tall (V2–V10) | Do not apply within 15 days before tassel emergence
Limited to no residual control |
| Steadfast Q | Accent + Resolve | Up to 20 inches tall (6 collars) | Best if applied when corn is <12 inches tall
Generally fair to good residual control |
| Touchdown | Emergence through V8 stage | Apply to Roundup Ready hybrids only.
No residual control |
|
| Yukon | Permit + dicamba | Spike to 36 inches tall /
Drop nozzles are permitted |
Residual control is fair to good on limited species |