When is applying herbicides to corn no longer viable?

Posted on 01/05/2017 in Featured, Sprayer, Video tips.

Herbicides can be applied to corn at many crop growth stages, though most labels identify a maximum—and sometimes minimum—growth stage at which herbicides should not be applied.

These non-application stages often depend on plant height or leaf stage—and are sometimes determined by both. If both growth stage indicators are included on product labels, the rule of thumb is to follow the more restrictive application instructions of the two.

There are many reasons for herbicide application restrictions, though some carry more significance than others. Particularly, when herbicides are applied to corn outside of their indicated growth period, there is a higher likelihood of crop injury.

See the maximum corn heights and growth stages, as recommended by the following herbicide brands:

Herbicide Maximum corn heights and growth stages*
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
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
Beacon Broadcast when corn is 4–20” tall. After corn is 20” tall or exhibits more than 6 collars use directed applications up to tassel emergence
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 must be made to corn from the 1-leaf collar stage through the 5-leaf collar (V5) stage
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/DiFlexx Duo Apply broadcast when corn is at the spike through 6-leaf collar (V6) growth stage, or 36” tall, whichever occurs first
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.
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.
Laudis Apply up to the V8 growth stage
Liberty (glufosinate-resistant corn) Broadcast until corn is 24” in height or in the V7 growth stage (7 developed leaf collars). Use drop nozzles for corn 24–36” 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
Shotgun Broadcast applications to corn up to 4 leaves or 8” tall; directed applications for 5-leaf or 8–11 ¾” tall corn
Solstice May be applied broadcast up to the V8 growth stage or 30” tall
Spirit Broadcast applications to corn 4–20” tall. Use drop nozzles when field corn is 20–24” tall or exhibits more than 6 collars (V6)
Starane Ultra Apply broadcast to corn with up to 5 fully exposed leaf collars (V5)
Status Do not apply to corn taller than 36” or past the V10 stage
Steadfast Q Apply to corn up to 20” tall or exhibiting 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

Source: University of Illinois June 9, 2016 by Aaron Hager
Corn&Soybean Digest June 10, 2016