Post-Direct Applied Herbicide Applications In Cotton
DR. LARRY STECKEL
JACKSON, TENN.
Some of the earlier planted cotton fields will soon be entering the true “laying it by” application timing. Given that some in 2020 were not successful spraying the same Palmer amaranth or junglerice multiple times with glyphosate + dicamba going back to an “old school” layby is a good plan.
A drawback to a post-direct or hooded application is that they are much slower than using a 100’ boom. That is true, but post-direct applications can be more efficient than multiple unsuccessful POST applications.
Post-direct Applications
Direx 16 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. This tankmix should be effective on barnyardgrass and junglerice if coverage is adequate and grasses are less than 6” tall. Depending upon the rate, Direx will provide residual control of Palmer amaranth.
Considerations: Direx will settle out in the tank when mixed with many formulations of glyphosate and MSMA, so aggressive tank agitation is a must. Sloppy post-direct of Direx will burn cotton leaves.
Clethodim 0.15 to 0.25 lbs/A + MSMA 2lbs/A – Equivalent to 6 to 10 ozs of Section Three or 10 to 16 ozs of Intensity + 2.66 pts of a 6 lb MSMA. Add one percent crop oil for better control.
Advantages: This would be a good choice for barnyardgrass, junglerice and goosegrass that escaped a dicamba + glyphosate application/s and/ or is large (>12”).
Considerations: This mixture will not control Palmer amaranth.
Hooded or Post-Direct Application
Liberty 32 ozs + Direx 32 oz/A or Caparol 32 oz/A or Valor 1.5 ozs/A or Zidua 1.5 ozs or Dual Magnum 16 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 additional surfactant is not needed. Most cotton now has good Liberty tolerance and sloppy post direct is not as damaging when tankmixed with Zidua or Dual Magnum.
Considerations: In order to protect from resistance developing, consider using a paraquat product if Liberty (glufosinate) 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 (>6”). As always with paraquat, be mindful of mix order and water pH. ∆
DR. LARRY STECKEL: Extension Weed Specialist, University of Tennessee
Palmer amaranth escapes after sequential POST dicamba + glyphosate applications in 2020