Tennessee Corn: Maturity Cutoffs for Herbicides

The corn across to Tennessee looks to be in pretty good shape.  The maturity of our corn crop has some variability do to some starting plating in early March while other fields were planted the last of April .

From rating corn weed control trials and walking a few corn fields this week it is very apparent that the pres that were applied in March to mid-April started breaking last week.  These PRE applications however, were not applied in vain as they have kept the weeds down until now. 

The corn in these fields can be cleaned up much easier as the weeds are very small.  Weeds in corn fields where no pre was applied have grown very large now and will be more difficult and expensive to control.

There have been some corn fields already treated most notably with Halex GT, Capreno, Armezon/Impact or Realm Q.  These herbicides like all corn herbicides work better when tankmixed with atrazine.  Unfortunately, for corn that is over 12” tall that is no longer an option. 

Do to the limited amount of days fit to spray there are a number of corn fields where the corn is well over the 12” height that will need to be sprayed.  One good substitute for atrazine on large corn to be tankmixed with some of the premixes is Status.    

These and other herbicides offer effective postemergence options even on large weeds, but there are cutoffs associated with all these.

Crop stage and/or crop height is used to determine the cutoffs for a given herbicide.  Often the label states the limits at whichever (crop stage or crop height) comes first.  Crop stage can easily be done by counting the number of collars that are fully open (ex.  4 open collars = 4 leaf).

Postemergence Corn Herbicides

Crop Height Cutoff

Crop Stage Cutoff

Accent

20 inches

6 leaf

Atrazine (Bicep, Degree Xtra, Acuron, etc.)

12 inches

8 leaf

Buctril

8leaf

Callisto*

30 inches (without atrazine)

Capreno*

7 leaf (without atrazine)

Corvus

2 leaf

Dicamba (Banvel, Clarity)

8 inches (1 pt/A) or
36 inches (1/2 pt/A)

5 leaf

Distinct

24 inches

Glyphosate – RR corn only

30 inches

8 leaf

Halex GT

30 inches

8 leaf

Hornet

24 inches

Armezon/Impact

8 leaf

Laudis

8 leaf

Liberty (Ignite) – LL corn only

24 inches

7 leaf

Diflexx

36 inches

6 leaf

Realm Q

20 inches

7 leaf

Resource

10 leaf

Resolve Q

20 inches

7 leaf

Status

36 inches

10 leaf

Steadfast Q

20 inches

7 leaf

Stout

16 inches

5 leaf

2,4-D

8 inches

*Note that if atrazine is added (to herbicides such as Callisto or Capreno for example), the cutoff would be reduced to 12 inches or 8 leaf.