Warm weather defoliation mixes (1 and 2 shot) with and without thidiazuron

Author: Tyson Raper, Cotton & Small Grains Specialist No Comments

Our forecast for the next 7 days contains ideal conditions for defoliating and opening bolls.  In this blog, I cover my current 1 and 2 shot go-to mixes and briefly describe how I would approach defoliation without thidiazuron.  

Since Friday (Sept 14), night temperatures have held well-above 65F, daytime temperatures have spiked over 90F, and the sun has decided to shine.  According to our current forecast, these conditions should hold for the next week.  Convincing our cotton crop to pitch leaves and open bolls under these conditions is much easier than in colder conditions- but you have to be cautious as to not over-shoot rate.  Recall that the development of abscission zones (the area at the base of the petiole which causes the leaf to shed from the plant) and boll sutures (the splits on each boll that cause them to open) are physiological processes; leaf shed and boll opening doesn’t occur in dead tissues.  Plants must be active for defoliation and boll opening to occur. Since the plants are very active under our current conditions, light defoliant rates will allow us to achieve defoliation.  Rates too high- particularly with our herbicidal products- will kill the leaf before the abscission zones can form.   

Several product combinations are fairly predictable under these conditions.  I’ve listed my 1 and 2 shot go-to mixes for our current conditions below.  As temperatures drop or rain/clouds enter the forecast, these will change.  Additionally, I’ve listed a few comments on how I would address defoliation if you cannot get thidiazuron.

1 shot (target 15-20 GPA with flat fan or hollow cone nozzles- coverage is critical)

Thidiazuron (Dropp, Daze, FreeFall) at 2-3 oz

Ethephon + cyclanilide (Finish, Terminate) at 16 oz

Ethephon (BollBuster, Prep) at 16 oz

*Under our current conditions, a Dropp + Finish + Ethephon mix will likely not need any tribufos (Folex) to achieve adequate defoliation.  However, if you have areas which were drought stressed or you would prefer to heat-up this mix, I would consider spiking with 2-4 oz Folex.

2 shot

Application 1:

Thidiazuron (Dropp, Daze, FreeFall) at 2-3 oz

Ethephon + cyclanilide (Finish, Terminate) at 16 oz

Application 2:

Tribufos (Folex) at 6 oz OR Aim/Display/ET at low rates**

Ethephon (BollBuster, Prep) at up to 26 oz (max season rate of 6 lb product is 42 oz)

**I prefer Folex in this mix if mostly large, mature leaves remain on the plant.  If you are addressing re-growth or juvenile leaves, consider Aim/Display/ET.  Keep in mind you will need an adjuvant for Aim/Display/ET, and low rates of adjuvant (and these products) should be applied under hot conditions to prevent desiccation.

Without thidiazuron

Our best regrowth control comes from thidiazuron.  Unfortunately, much of our crop this year has tremendous regrowth potential and thidiazuron is becoming more difficult to find.   Many have indicated they may try to get regrowth control from pre-mixed thidiazuron + diuron products (Ginstar, Adios, Cutout). Unfortunately, it takes 4 oz of Ginstar/Adios/Cutout to get the same rate of thidiazuron as 1 oz of Dropp/Daze/FreeFall.  Attempting to get the same rate of regrowth control with Ginstar/Adios/Cutout is extremely risky, since many have noted high rates of dessication with diuron at our current temperatures.  Subsequently, I prefer to hold Ginstar/Adios/Cutout out of my mix until temperatures begin to drop.

1 shot without thidiazuron

Tribufos (Folex) at  4-6 oz

Ethephon + cyclanilide (Finish, Terminate) at 16 oz

Ethephon (BollBuster, Prep) at 16 oz

2 shot without thidiazuron

Application 1:

Tribufos (Folex) at  4-6 oz

Ethephon + cyclanilide (Finish, Terminate) at 16 oz

Application 2:

Tribufos (Folex) at 6 oz OR Aim/Display/ET at low rates***

Ethephon (BollBuster, Prep) at up to 26 oz (max season rate of 6 lb product is 42 oz)

***Again, I prefer Folex in this mix if mostly large, mature leaves remain on the plant.  However, there is a good chance you will likely need to address re-growth and/or juvenile leaves if thidiazuron is not included in the first application.  Subsequently, you will likely need to consider Aim/Display/ET in the second application.  Keep in mind you will need an adjuvant for Aim/Display/ET, and low rates of adjuvant (and these products) should be applied under hot conditions to prevent desiccation.

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