Maximizing Defoliation with Limited Supplies of Thidiazuron

With defoliation either underway or at hand in the eastern Cotton Belt, reports about the limited availability of thidiazuron (TDZ) have caused growers to raise concerns about how the shortage could affect this season’s defoliation efforts.

Since thidiazuron is a key component of many cotton defoliation tankmixes and helps prevent regrowth after defoliation, Dr. Jared Whitaker, University of Georgia Extension cotton agronomist, and Mark Freeman, Extension agronomist in east Georgia, issued a white paper with thoughts and suggestions for growers to consider.


In general, they suggest that growers:

  • Use the TDZ they have wisely. If regrowth potential is low, then consider rates between 1.5 to 2.0 oz/A. If regrowth is expected and a lot of juvenile tissue is present, consider higher rates between 3.0 to 4.0 oz/A.
  • If no TDZ is available, mixtures of ethephon + Ginstar (TDZ + diuron) can be very effective at removing juvenile tissue and preventing regrowth. An 8 oz/A rate of the Ginstar products has 2.0 oz of TDZ (a 4 lb ai/A TDZ product) and 1.0 oz of diuron (4 lb ai/A diuron product).
  • If TDZ isn’t available and Ginstar products are not used, be aware that regrowth can be more troublesome and harvest as timely as possible.
  • If no TDZ is available and regrowth potential is lower, the mixture of ethephon + tribufos (Folex) can be very effective.
  • Mixtures of ethephon + PPO herbicides (ET, Aim, Display, etc.) can also  be effective. However, these mixtures are sometimes less consistent than mixtures of ethephon + tribufos (Folex) and, in general, are more consistent later in the defoliation window.