Even for our latest cotton, given an average frost date of around October 15, this is the last week you can likely justify insecticide applications to cotton.
Based on average historical temperatures, the last effective bloom date was two week ago. A late flurry of bollworm moth activity has forced some sprays this week, and most folks are electing to go cheap (pyrethroid + acephate) because residual control in less important at this late date. With some exceptions, I agree with this strategy.
I’ve had a few complaints about Besiege or Prevathon, but the opposite is also true. In my tests, those products have performed as expected. I think expectations are set a little too high. We do not have foliar-applied insecticides that will provide flawless control of bollworm. Some worms are sneaky about staying in and under bloom tags or within a boll for a week if not longer at times. Although you will winnow some of them out over time, you will also find worms that you expected to be dead.
It’s understandable that people get annoyed by seeing survivors after application given the relatively high costs of these products. But we all know the underlying problem is the need to spray 2-gene cotton, sometimes twice, for bollworm control.
A reminder: “cut out” occurs when a field hits NAWF=5. Flowers present at this time represent the last bolls you are likely to pick. Several folks have mentioned wanting to protect the “top crop,” meaning blooms, squares, and very small bolls. If you are sitting at NAWF 3 or less, you can bet the farm any of those fruit will shed, or, in later cotton, have little chance of making it into the picker basket before a frost. Any applications now are meant to protect bolls that are at least 10-15 days old.