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 |
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.
My bicep application has held on much longer than I thought it would. However, I noticed some Johnsongrass coming back today in my conventional corn. What’s the best controller for Johnsongrass in conventional corn? Thanks for your help.
Wendy
Steadfast or Accent would probably be the best choices.
Thanks for the question
Larry