Cotton Defoliation

I have been asked if I have seen any yet. I’ve seen a few fields defoliated this week, all dryland fields. Many fields are approaching defoliation. Here are some thoughts from UGA Extension Cotton Agronomist Dr. Jared Whitaker:

1. Timing – 60 – 75% open bolls OR 3 to 4 nodes above cracked boll.
   Growers want to wait until later, with this year could lose significant yield and quality if weathering occurs and lower positions rot or fall off. I’m always happier if we go earlier than later.
2. Defoliation mixes – There are a thousand RIGHT ways to do it. To keep from getting bogged down with the details and because it’s the most consistent effective treatment we have I always start with what I call the “3-WAY” idea.
   This 3-way includes ethephon (PREP), Thidiazuron (Dropp, TDZ, Freefall) and Tribufos (Def or Folex).
3. Adjuvants – (1) You don’t need one if you have Tribufos in the mix (2) if the label requires it, then its ok, the PPO herbicides (Aim, ET, Display, etc.) require them. (3) Adjuvants most always heat the mix up which can be ok later in the year in cooler conditions.
4. Water Volume – MORE WATER THE BETTER, I would love it if everyone use 20 GPA with defoliant applications. 15 GPA is ok, but it’s important for me to point out that I can use less product and be more effective if I use higher rates of water. Airplanes – they only go 2.5 to 5 GPA, but if done properly product is pushed into the canopy and often aerial applications can be just as good as ground applications.
5. MORNINGGLORIES – Our herbicide programs have become weak on MG’s and often we think about using something in the defoliation mix to help with harvest. A couple of thoughts on this. (1) the vines are the issue for cotton harvest and remember where they are when the canopy is full before defoliation (2) several products work with MG’s and all are PPO herbicides (which I consider to be very inconsistent with regards to defoliation this time of year compared to folex) (3) if I was going to include it in defoliation, I would use it in place of folex in the three way or (I like better) cut the folex rate back significantly. (4) MY THOUGHTS ON HOW TO HANDLE MORNINGLORY IN COTTON FIELDS THIS TIME OF YEAR — use a normal defoliation mixture and wait till at least the upper canopy is defoliated (5-8 days), then mix up your MG product and spray where needed. This will be much more effective on MG and also be a way to clean up what the first shot of defoliant missed.
6. PRICES – Cotton producers are facing situations with $ related to cotton prices. Often there are growers who want to defoliate the crop as inexpensively as possible. I truly understand their situation and realize that growing cotton isn’t cheap, but having said that I think we can defoliate most of our crop for less than $15 per acre, and more importantly less than $10 per acre this time of year (WITH the 3-way mixes in the presentation). I know that’s a lot of money, but we’ve gotten this far and its important to do a good job with defoliation. You can go cheaper with some other options, but most all of the time they are less effective and less consistent and really aren’t that much cheaper.