It’s that time of year again. Time to start thinking about terminating our cotton crop and getting the plants and bolls ready for harvest.
Cotton defoliation is much easier when there is a good boll load and all of the available nutrients have been used by the crop. The timing of defoliation is critical to insure optimum yield and fiber quality. To determine timing, we use a combination of percent open bolls and nodes above cracked boll (NACB). To determine NACB you count nodes above the highest first position cracked boll looking for bolls that are expected to be harvested. To determine boll maturity bolls should be cut to expose seed. mature seed will have a brown or black coat with cotyledon leaves developed within. We are typically wanting 4 NACB before we make defoliation decisions.
Most growers that I work with are already using a 3-way mixture so the only thing we may need to do is make sure our rates are right for the weather or temperatures. As temperatures begin to drop into the 70’s it is time to start considering the addition of a combination of diuron + thidiazuron (ex. Ginstar) The diuron helps when temperatures are cooler and the recommended rate would be 6-8 oz/acre.
Thidiazuron tends to lose activity especially when night temps drop below 65.
As always ethephon (ex. Prep) needs to be in the tank with these products and you may want to consider using the high rate of 42 oz/acre.
Adding tribufos (ex.Folex) to the mixture is fine, but our specialists say, you can get excellent activity with thidiazuron + diuron +ethephon.
Looking at the 10 day forecast a standard 3-way mixture for this time of year would be 12oz/acre Folex, 6.4 oz/acre Ginstar and 42 oz/acre Prep. Not sure what Ian is going to do, but it looks like it will at least bring us some rain, hopefully not too much wind, and we can get back in the field quickly to start getting this cotton crop ready for the picker. To make the most of your application it is recommended that you use a minimum of 15 gallons of water per acre. It will take a little more time, but in the end, you want coverage of the entire plant, not just the top 1/2.
Contact your County Agent if you have questions.