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Corn growth stage cutoffs for postemergence herbicide application

Sachin Dhanda, Weed science postdoctoral researcher, Sithin Mathew,  Weed science graduate student, and Debalin Sarangi, Extension weed scientist

Figure 1. Corn field planted in mid-May requires
 postemergence herbicides for weed control.
Photo: Debalin Sarangi
This season’s erratic weather has resulted in very few good spray days in Minnesota, leaving some corn acres without a postemergence herbicide application. Many fields received postemergence treatments very early in the season, prompting farmers to consider a second application to control problem weeds like waterhemp. Herbicide labels typically specify growth stage or crop height cutoffs (whichever comes first) for herbicide application, and the preharvest intervals (PHI) indicate the minimum time required between the last herbicide application and crop harvest. The restrictions are crucial to prevent potential crop injury, herbicide carryover, environmental or food safety issues, and other potential concerns. When tank mixing herbicides, the most restrictive label determines the cutoff. Always consult herbicide labels before application to ensure compliance. Below is an updated table (as of July 3, 2024) summarizing corn growth stage or height cutoffs and PHI for commonly used postemergence herbicides.

Table 1. Commonly used postemergence herbicides in corn with their application restrictions.
Herbicide Active ingredient Corn height/
growth stage cutoff
Preharvest interval
2,4-D 2,4-D Less than 8"; direct spray
to 8" to tasseling
7 days
AAtrex 4L atrazine 12" 60 days for forage
Accent Q nicosulfuron 20"/V6; use drop nozzle for
corn up to 36" tall or V10 stage
70 days for grain and 
45 days for forage
Acuron atrazine +S-metolachlor
+ mesotrione
12" 60 days for forage
Acuron Flexi S-metolachlor +
mesotrione +
30"/V8  60 days
Acuron GT (only
Roundup Ready
S-metolachlor +
glyphosate + mesotrione
+ bicyclopyrone
30"/V8  45 days
Aim EC carfentrazone-ethyl V8; use drop nozzle up to V14 -
Anthem Maxx fluthiacet methyl +
V4 70 days for grain and 
30 days for forage
Armezon PRO topramezone +
30"/V8 45 days
Basis Blend rimsulfuron +
6"/V2 30 days
Bicep II Magnum atrazine + S-metolachlor 12" 60 days for forage
Cadet fluthiacet-methyl Up to 48" but before tasseling -
Callisto mesotrione 30"/V8 45 days
Callisto Xtra atrazine + mesotrione 12" 60 days
Capreno thiencarbazone-methyl
+ tembotrione
20"/V7; V5 stage for seed corn 45 days for forage
Clarity, Banvel dicamba 8"/V5 stage (1 pt/A rate); 36" 
or 15 days before tassel 
emergence (0.5 pt/A rate)
DiFlexx dicamba 36"/V10 45 days for forage and 
grain harvest can be done
when crop reaches milk
DiFlexx Duo dicamba + tembotrione 36" or up to (but not including)
V7; directed spray V7 to V10 
or up to 36" tall or up to 15
days prior to tassel
45 days for forage and
grain harvest can be done
when crop reaches milk
Dual II Magnum  S-metolachlor 40" 30 days for forage
Enlist Duo (for 
Enlist corn)
2,4-D + glyphosate 30"/V8; use drop nozzles from 
30 to 48"
50 days for forage
Enlist One (for
Enlist corn)
2,4-D 30"/V8; use drop nozzles from 
30 to 48"
30 days for forage
Halex GT (for 
Roundup Ready 
S-metolachlor + glyphosate
+ mesotrione
30"/V8 45 days
Harness Max acetochlor + mesotrione 11" 60 days
Hornet flumetsulam + clorpyralid 20"/V6; use drop nozzles from
20 to 36"
85 days for grain and
45 days for forage
Impact topramezone - 45 days
Impact Z atrazine + topramezone 12" 45 days
Katagon tolpyralate + nicosulfuron 20"/V5 70 days
Kyro acetochlor + clopyralid
+ topramezone
24" 45 days for forage
Laudis tembotrione V8 45 days for forage
Liberty 280 SL
(for LibertyLink
glufosinate V6; Use drop nozzles up to
36" height
70 days for grain and 
60 days for forage
Maverick pyroxasulfone + mesotrione
+ clopyralid
18"/V6 30 days
Outlook dimethanamid-P 12"; direct application should 
be made from 12 to 36"
40 days for forage
Perpetuo flumiclorac + pyroxasulfone V6 28 days for forage
Realm Q rimsulfuron + mesotrione 20"/V6 70 days for grain and
45 days for forage
Resicore XL acetochlor + mesotrione 
24" 45 days
Resolve Q rimsulfuron + thifensulfuron 20"/V7 30 days for forage
Resource flumiclorac pentyl  V10 28 days for forage
Revulin Q nicosulfuron + mesotrione 20"/V6; Use drop nozzles from
20 to 30"
70 days for grain and 
45 days for forage
(for Roundup 
Ready corn)
glyphosate 30"/V8; Use drop nozzles from
30 to 48" tall
50 days
Shieldex 400SC tolpyralate 20"/V6 45 days for grain and 
21 days for forage harvest
Sinate (for 
LibertyLink corn)
topramezone + glufosinate 24"/V7; Use drop nozzles from
24 to 36" corn
70 days for grain and 
60 days for forage
Status dicamba + diflufenzopyr 36"/V8 72 days for grain and 
32 days for forage
Stinger clopryalid 24" 40 days for forage
Storen bicyclopyrone + mesotrione
+S-metolachlor +
V8 45 days
Surestart II acetochlor + flumetsulam
+ clopyralid
11" 85 days
Tough 5EC pyridate V8 68 days
Warrant acetochlor 30"; Use drop nozzles for
24 to 30"
40 days for forage
WideMatch clopyralid + fluroxypyr V5 90 days
Yukon halosulfuron-methyl +
20"; Use drop nozzles for 
20 to 36"
30 days for forage
Zidua SC pyroxasulfone V8 -

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