by: Aaron Hager, University of Illinois
The labels of most postemergence corn herbicides allow applications at various crop growth stages, but almost all product labels indicate a maximum growth stage beyond which broadcast applications should not be made, and a few even a state minimum growth stage before which applications should not be made. These growth stages are usually indicated as a particular plant height or leaf stage; sometimes both of these are listed. For product labels that indicate a specific corn height and growth state, be sure to follow the more restrictive of the two. Application restrictions exist for several reasons, but of particular importance is the increased likelihood of crop injury if applications are made outside a specified growth stage or range. The following table lists the maximum corn growth stage for broadcast application of several postemergence corn herbicides. Be sure to constult the respective product label for additional precautions or restrictions.
Table 1. Postemergence herbicide application timings based on corn growth stage(s).
| Herbicide | Maximum corn heights and/or growth stagesa |
| 2,4-D | Broadcast before corn exceeds 8” tall; use drop nozzles when corn is taller than 8”. |
| Accent Q | Broadcast up to 20” tall or through the V6 stage. Apply with drop nozzles when corn is 20–36” tall or before the V10 stage. |
| Anthem Maxx | Apply from corn emergence through the V4 (visible fourth leaf collar) stage. |
| Armezon Pro | Apply from corn emergence to the 8-leaf stage or 30” tall. Use directed applications when corn is 12–30” tall. |
| Atrazine | Apply before corn exceeds 12” tall. |
| Basagran | No height specified on label. |
| Basis Blend | Apply to corn from spike through 2 collar stage. Do not apply to corn having 3 fully emerged collars or over 6” tall. |
| Cadet | Apply until corn is 48″ tall or prior to tasseling. |
| Callisto/Callisto GT | May be applied to corn up to 30” tall or up to the 8-leaf stage. |
| Callisto Xtra | Apply before corn exceeds 12” tall |
| Capreno | Broadcast applications may be made to corn from the 1-leaf collar stage up to 20” tall. Do not apply if corn is more than 20” tall or exhibiting 7 or more leaf collars. |
| Clarity or Banvel | Apply between corn emergence and the 5-leaf stage or 8” tall; apply 0.5 pt/A rate when corn is 8 to 36” or if 6th leaf is emerging, or if 15 days prior to tassel emergence. Do not apply when soybean are growing nearby if: 1) corn is more than 24” tall, 2) soybean are more than 10” tall, 3) soybean have begun to bloom. |
| DiFlexx | Apply broadcast to corn from spike through V10 growth stage or 36” tall, whichever occurs first. |
| DiFlexx Duo | Apply broadcast to corn from emergence up to, but not including, V7 or 30” tall, whichever occurs first. Can be applied as a directed spray from V7 through V10, up to 36” tall corn, or up to 15 days prior to tassel, whichever occurs first. |
| Enlist One/Duo | Apply when corn is no larger than V8 or 30” tall, whichever is more restrictive. Directed applications can be made to corn up to 48” tall. |
| Glyphosate (glyphosate-resistant corn) | Apply broadcast through the V8 stage or until corn reaches 30” tall. Use drop nozzles for applications to corn 30–48” tall. |
| Halex GT (glyphosate-resistant corn) | Apply to corn up to 30″ tall or the 8-leaf stage. |
| Harmony SG | Apply to 2–6 leaf corn with 1–5 collars or up to 16” tall. |
| Harness Max | Apply until corn reaches 11” tall. |
| Hornet WDG | Apply broadcast until corn reaches 20” tall or V6 stage. Apply with drop nozzles to corn up to 36” tall. |
| Impact/Armezon | Can be applied up to 45 days before harvest. Do not apply Armezon past the V8 growth stage. |
| Impact Z | Apply before corn exceeds 12” tall. |
| Laudis | Apply up to the V8 growth stage. |
| Liberty (glufosinate-resistant corn) | Broadcast until corn at the V6 growth stage. Use drop nozzles for up to 36” tall. |
| Marksman | Apply between corn emergence and the 5-leaf or 8” height stage. |
| Moxy | Apply prior to tassel emergence. |
| NorthStar | Broadcast applications are made when corn is between 4 –20” tall (V2–V6). Use directed applications when corn is 20–36” tall. |
| Permit | Can be applied from spike through layby. |
| Realm Q | May be broadcast applied to corn up to 20” tall or exhibiting 6 leaf collars. |
| Require Q | Apply to corn 4–20” tall. Do not apply to corn exhibiting 7 or more leaf collars. |
| Resolve Q | Do not apply to corn taller than 20” or exhibiting 7 or more leaf collars. |
| Resource | Apply to corn from the 2-leaf through 10-leaf stage. |
| Revulin Q | Do not apply to corn taller than 30” or that exhibits 8 or more collars. |
| Solstice | May be applied broadcast up to the V8 growth stage or 30” tall. |
| Starane Ultra | Apply broadcast to corn with up to 5 fully exposed leaf collars (V5). |
| Status | Can be applied to corn between 4” (V2) and 36” (V8) tall. |
| Steadfast Q | Apply to corn up to 20” tall and exhibiting up to 6 leaf collars. |
| Stinger | Apply to corn from emergence through 24” tall. |
| Yukon | Apply broadcast or with drop nozzles to corn from spike to 36” tall. Drop nozzles are recommended when corn exceeds 20”. |
| Zemax | May be applied after corn emergence until plants reach 30” tall or up to the V8 stage. |
a When maximum application timings are indicated by two corn growth stages, follow the most restrictive of the two.