02 Jun Tips for Applying Residual Herbicides after Corn Emergence
Reference: http://www.agriculture.com/crops/pesticides/herbicides/tips-f-applying-residual-herbicides_179-ar49027
Cool weather and wet soil conditions throughout areas in the Midwest have disrupted the normal sequence of early season field operations. One of those happens to be pre-emergence herbicide applications.
The application of soil residual herbicides is important because usually they deliver several weeks of weed control, cover a broad spectrum of weeds, and aid in weed resistance management by incorporating additional site(s) of action, say Amit Jhala, Extension weed management specialist at the University of Nebraska-Lincoln, and Lowell Sandell, Extension weed science educator.
“This year many Nebraska cornfields were planted, but due to wet soil conditions, pre-emergence herbicides were not applied,” the experts say. “We have received phone calls from corn growers about options for applying soil residual, pre-emergence herbicides after corn emergence.”
If your applications have been delayed until after corn emergence, there are still several options available for you to use.
There are several residual, pre-emergence herbicides such as Breakfree, Dual II Magnum, Harness, Keystone, Prowl H2O, Warrant, Zidua that can be applied after corn emergence without injury to corn, they say. But remember, these products won’t kill weeds present at the time of application.
“These products do not have foliar activity and will not control weeds present at application,” say Jhala and Sandell. “Therefore, they should be tank-mixed with foliar herbicides labeled for corn. Some of the herbicides, including Anthem ATZ, Bicep II Magnum, Breakfree ATZ Lite, Confidence Xtra, Degree Xtra, FulTime NXT, Keystone LA NXT, Lumax EZ / Lexar EZ, Stalwart Xtra, and Volley ATZ NXT contain active ingredients (such as atrazine) that have foliar activity.”
Consult the label
When applied at the correct weed growth stage, they will provide burndown activity. Check the label for additional information, such as the need for tank-mix partners or spray additives to improve control of existing weeds. Also, application timing and other restrictions of tank-mix herbicide partners as noted in on the label.
“Attempting to save a trip across the field by applying an herbicide with a liquid nitrogen fertilizer solution, such as 28% urea ammonium nitrate (UAN), as the carrier is not advisable if corn has emerged,” say Jhala and Sandell. “Tank-mix partners may cause other effects regardless of the application timing.”
When applying residual herbicides after corn emergence, consider these factors:
Crop stage
Weed height
Tank mix partner
For weeds such as glyphosate-resistant marestail, giant ragweed, common waterhemp, and kochia residual herbicides have been reported to be an effective tool for control, say Jhala and Sandell. However, the length and effectiveness of the residual active will vary based on:
Weed species
Application rate
Rainfall following the application
Density of the weed and crop canopy at the time of application
Length of subsequent weed germination events
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