Georgia cotton farmers who were kept out of their fields by wet conditions are now waiting for their late-planted crop to mature. University of Georgia cotton expert Guy Collins estimates 30 percent of the crop still needs to be harvested.
Before cotton can be harvested, the plant’s leaves must be removed through a process called defoliation. Knowing the precise moment to defoliate can enhance yield potential and avoid profit losses.
To speed up this natural process, farmers spray a mix of various chemicals on cotton plants, Collins said. Just like trees, cotton leaves change color and fall off. “If the plant is close to doing that on its own, we speed it up for them,” said Collins who is based on the UGA-Tifton campus.
Farmers scout fields to determine when to defoliate. Collins says scouting should involve covering all areas of a field if different variables are involved, such as one end of the field is taller with more immature bolls toward the top.
Normal defoliation methods are used during warmer weather. But, many of these methods are less consistent in cooler weather, he said.
And boll development slows down considerably in cooler temperatures and usually ceases when a frost occurs. Collins said this happened in Georgia a couple of times in November.
“If the plant’s not ready, we can’t make (maturity) happen,” Collins said. “We can get the leaves off but you might prevent some bolls from opening.”
Defoliation is typically done two weeks before harvesting. Sometimes the wait is as short as 10 days, but it can take as long as 21 days for the leaves to fall off the plant. And bolls require more time to open. In some cases, a second spray is necessary to remove all the foliage.
Cotton farmers have three objectives when defoliating cotton: (1) Remove the leaves from the plant; (2) Open the bolls or accelerate the boll-opening process; (3) Remove or prevent regrowth or young juvenile growth.