Post-Direct or Hooded Options for Layby Weed Control
July 6, 2017 By Larry Steckel, University of Tennessee Extension Weed Specialist
Many cotton acres are nearing the true “laying it by” application timing. Given all the drift issues, going back to an “old school” layby is a very good plan.
Liberty has displaced glyphosate as the most common herbicide in a post-direct or hooded application in recent years. Below are some thoughts on several post-direct mixtures:
Post-direct Applications
Direx 12 to 24 oz/A + MSMA 2lbs/A – Cotton must be at least 6 inches tall for the Direx 12 oz rate. Surfactant is not needed if the MSMA used has a surfactant included.
Advantages: Economical. Direx + MSMA can provide control of emerged horseweed and Palmer amaranth less than 6” tall. Direx, depending upon the rate, will provide residual control of horseweed and Palmer amaranth.
Considerations: Direx will settle out in the tank when mixed with many formulations of glyphosate and MSMA, so aggressive tank agitation is necessary. Sloppy post-direct of Direx will burn cotton leaves.
Suprend 1.25 lbs/A – Equivalent to 32 ozs of Caparol + 0.15 ozs of Envoke/A. Add 1% crop oil for better control.
Advantages: Good control of many grasses and broadleaf weeds, including pigweeds and morningglories. Caparol is one of the better residual herbicides for pigweed control. This premix in our studies has suppressed growth of small horseweed.
Considerations: This premix will not control grasses. The addition of MSMA 2.67pts/A of 6L formulation or glyphosate at 0.75 lbs ae/A will control grasses.
Hooded or Post-Direct Applications
Liberty 32 ozs + Direx 16 oz/A or Caparol 32 oz/A or Valor 1.5 ozs/A or Zidua 1.25 ozs or Dual Magnum 12 ozs. Cotton must be at least 6 inches tall.
Advantages: It will control horseweed up to 10 inches in height. Good control of many broadleaf weeds, including Palmer amaranth and morningglory species. Liberty has a lot of surfactant already present, so surfactant is not needed. Most cotton now has good Liberty tolerance, and sloppy post direct is an option when tankmixed with Zidua or Dual Magnum.
Considerations: In order to protect from resistance developing, consider using a paraquat product if Liberty has already been applied over the top.
Hooded only Applications
Paraquat (Gramoxone Inteon 32 oz/A) + Direx 16 oz/A or Caparol 32 oz/A or Valor 1.5 ozs/A. Cotton must be at least 12” tall.
Advantages: This is the most consistent mixture to control large Palmer (>12”).
Considerations: Needs to be applied carefully! Use 0.25% COC for best results on large Palmer.
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