Weekly Defoliation Recipe:
- 3.2 – 4 oz/acre thidiazuron (Dropp), using the higher end of the range where regrowth potential is greater
- 8 – 10 oz/acre tribufos (Folex/DEF), with higher rates on cooler days
- 32 – 42 oz/acre ethephon (Prep, Setup, SuperBoll)
The forecast looks favorable this week with little concern for rainfall, although there are some low chances of rain over the weekend. Keep that in mind as we approach the end of the week. A big part of deciding what to do from a defoliation standpoint is not just looking at the weather forecast, but also considering what happened over the last few days. Many of us received rainfall last week, which means that if any residual fertility remains in the field, this crop may start regrowing if it hasn’t already. Only one chemistry controls regrowth: a thidiazuron product (Dropp, Klean-Pik, Freefall, etc.). Given the rain we received last week and the potential for regrowth, I believe we need to increase the rate of thidiazuron. For the other products, including Folex and most PPOs, as well as Prep, Setup, and SuperBoll, rates generally increase as temperatures decrease. The plant is less active at lower temperatures and may need a little more help getting the message, so higher rates are often needed. One exception is ETX. If someone chooses to use ETX, I recommend using 1 oz/acre across the board along with a surfactant. Another exception is that thidiazuron activity drops significantly when temperatures fall below 65°F. When temperatures reach that level, I typically remove thidiazuron from the mix and may switch to a Ginstar-type product instead. Speaking of Ginstar, Diuron alone is not labeled for defoliation. The only legal way to use diuron as a defoliant is through labeled products such as Ginstar, Cutout, Adios, and similar formulations. In my experience, it doesn’t add anything beneficial, so I don’t see a reason to go through the trouble. Also, regarding surfactants or AMS with defoliants. Unless the label specifically requires them, I do not recommend them. With PPO products, the label directs users to include either a crop oil concentrate (COC) or a nonionic surfactant (NIS). However, if you are using the standard three-way mix, a surfactant is not required according to labeled directions.