By Dr. Camp Hand
First, this week it’s gonna be cool. Once we get past Wednesday, highs hardly come out of the 60s and lows are going to be in the 30s to 40s. As we all know, cotton growth and development is based on DD60s, with growth occurring mainly between temperatures of 60 to 94 degrees F. Once temperatures get below 60, cotton growth and development are minimal. This is important to keep in mind when considering when to defoliate.
Not only does the temperature impact crop growth and development, but as I have harped on, it also affects product efficacy. This week, I would probably take Dropp out of the mix. Below 65 F you don’t get much out of it. Increased rates of Folex will be necessary (right around a pint/acre), and then I would go with the highest labeled rate of Prep. As mentioned in the last email, I am a big fan of what I have seen out of Ginstar and would consider that as an option as well. Surfactants will likely increase uptake and efficacy in cooler situations like we are seeing, so I would consider adding one to the mix.
Another thing we need to start thinking about is first frost dates. In my opinion, we need to be ahead of the first frost to get as much benefit as possible out of our defoliants. Generally, you want to defoliate 2 to 3 days ahead of a frost to get those defoliants working before the plant shuts down. I looked at a few locations on the UGA Weather Monitoring Network to get averages on first frost dates for what I consider fairly representative locations across the state:
SW GA – November 29 (Tifton)
SE GA – November 20 (Statesboro)
NE GA – November 12 (Watkinsville)
NW GA – November 3 (Rome)
Keep in mind that these are averages over the past 17 years meaning it could be earlier or later, just depends on the year.
I have had a couple of conversations with agents and consultants this week about when our crop is “done”. In my mind, we are quickly approaching the point at which we aren’t gaining much be leaving the leaves on our cotton crop. Even if it is a late planted crop and only 30 to 40% open, I would consider trying to spray it this week. I know for many that logistically may not be possible as most folks are still finishing up peanuts, but as mentioned earlier, you want to defoliate when you are still getting activity out of your defoliants.