Tennessee Corn: Maturity Cutoffs for Herbicides

Photo: University of Minnesota

Photo: University of Minnesota

Due to little time and very few good spray days some corn fields have yet to have their lay-by application. Corn is putting on a new leaf every 3 days with all the heat and water. Therefore time is short before it will be too mature to apply any herbicide safely over the top.



The most asked question “is how large can corn be before glyphosate could potentially cause injury”? The glyphosate label states it can be applied up through the V8 corn growth stage. My experience has been if glyphosate is applied to corn larger than that it can at times cause ears to be barren.  This phenomena is difficult to predict ahead of time as it can vary due to maturity of the corn at application, hybrid and weather.

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 leaf collars that are fully exposed (ex.  4 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

Roundup PM

8 leaf

Status

36 inches

10 leaf

Steadfast Q

20 inches

7 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.

Source URL: https://news.utcrops.com/2020/06/corn-maturity-cutoffs-for-herbicides-2/