Many cotton acres are nearing the true “laying it by” application timing. Given how Palmer amaranth just keeps coming this year these directed applications have become critical for consistent control of glyphosate-resistant (GR) Palmer amaranth.
Ten years ago a typical post-direct or hooded application would contain glyphosate plus another herbicide to provide a residual component. Times have changed and glyphosate is seldom added to these mixtures as in all most all cases the target is Palmer amaranth. Below are some of our thoughts on several post-direct mixtures.
Direx 12 to 24 oz/A + MSMA 2lbs/A – Cotton must be at least 6” 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 one percent 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 Application
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” tall.
Advantages: It will control horseweed up to 10” in height. Good control of many broadleaf weeds including Palmer amaranth and morningglory species. Liberty has a lot of surfactant already present so surfactant not needed. Most cotton now has good Liberty tolerance an 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: Need to be applied carefully! Use 0.25% COC for best results on large Palmer.