Two-Pass Herbicide Applications In Corn Provides More Consistent Weed Control
DR. LARRY STECKEL
JACKSON, TENN.
Corn planting started in West Tennessee this past week. With corn planting in mind, I keep seeing an advertisement on TV about one-pass programs providing season-long weed control. This advertisement might be true in some places but not in our neck of the woods.
In our research time and time again the most consistent weed control in corn is acquired with some type of two-pass approach. Indeed last summer many folks found that they needed to apply a “rescue” herbicide application after the PRE-applied played out in their corn. The problem was many found out too late that the PRE was gone and were calling asking how to control 18 to 24” Palmer amaranth in their big corn.
Given the rain we typically get in March and April it is not surprising that PRE applied herbicides may give out well before the corn can shade the row middles. Last year, for example, in our corn weed control research at Jackson, 1.5 lbs/A rate of atrazine or 2 qts/A of Bicep provided about 2 to 3 weeks of residual control. Even the more robust pre applied premixes like Lexar, Corvus or even Fierce were breaking with weeds about 4 weeks after application.
Springs that have wet periods are more the norm than the exception. That is why a two-pass corn weed control program in 9 out of the last 10 years has provided more consistent weed control than a single pass program. This could be one of those years that is the exception, but the odds are pretty long.
As far as what herbicide/s to be applied PRE in a two-pass program the list is fairly extensive. However, many hate to lock themselves in to corn if they don’t get a stand and it gets too late to replant. With this in mind, herbicides that can be used PRE in corn with the option to come back to replant grain sorghum or soybean would be Dual Magnum, Sharpen, Verdict and Warrant.
As far as managing those large Palmer in large corn a combination of Halex GT plus Status, or Capreno plus Status, or Realm Q plus Status has provided >90 percent control. The corn height restriction for Halex GT is 30” and the corn maturity restriction for Capreno is 7-leaf corn and the height restriction for Realm Q is 20” or 7-leaf corn. Status can be applied to corn from the V2 to V10 (or 36” tall) corn height stages. ∆
DR. LARRY STECKEL: Extension Weed Specialist, University of Tennessee