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How best to approach late-season cotton management?

How best to approach late-season cotton management?

Last effective bloom date. Fruit retention and plant height management.  

As of Aug. 13, the Mississippi cotton crop was close to the last effective bloom date.

“In Tunica County, based on 30 or 40 years of weather data, the last effective bloom date is about Aug. 14,” said Darrin Dodds, Mississippi State University Extension cotton specialist, at the Late-Season Crops Field Day at the Delta Research and Extension Center in Stoneville. “As you move south (towards Stoneville), it’s Aug. 20 to Aug. 22. Farther south, it may be Aug. 25, depending on the weather.

“So, say it’s Aug. 22, that’s basically telling you that there’s a good chance that a bloom on the plant will make it into the picker basket. As the season progresses a week, or two, past that the chances get progressively lower to get that bloom harvested.”

The reason that matters, said Dodds, is “it can help you tailor some of your management decisions. We have a crop that’s a little late because of planting date. We tended to plant around three or four windows because of the rain, wind and weather.” 

To illustrate several things, including the importance of fruit retention, Dodds held up two plants freshly pulled from test plots. “The only difference between these two plants is the way they were managed for plant bugs. There’s about an eight-inch high difference. (The untreated plant) has less fruit compared to the (treated plant), which is running 80-plus percent fruit retention versus (the untreated) at 20 to 30 percent. That shows you what a good fruit load will do with respect to height management in cotton.”

Recently, Dodds has fielded many questions about late-season cotton. “Folks are asking, ‘What do I need to do with plant growth regulators to try and stop this crop?’ I’ve been telling them that at this time of year you don’t need any more vertical growth on that plant. All that will do is make a switch at the top of the cotton plant. … If there’s one thing people hate to see in a cotton field is a switch at the top of a plant. It makes people mad to even see it.

“However, my phone has been ringing about what to do with this crop. When you get into some of the more aggressive type varieties -- Phytogen 499 or DPL1321 to some degree, even a Stoneville 4946 -- and you take the fruit retention down, it makes it that much harder to control from a vertical standpoint.”

Knocking off leaves

Dodds held up the treated plant again. “This one is much easier to control. It has a good fruit load and is somewhat regulating itself because of that. It won’t be much trouble to control the plant height.”

There are several reasons to keep the vegetative height under control. First, said Dodds, is better penetration of herbicides and insecticides. “Jeff (Gore, MSU entomologist) could probably write a book about how much more difficult it is to kill plant bugs in cotton that’s big and tall and rank and lush versus shorter, more compact plants.”

Another consideration is harvest efficiency. “Think about cotton that’s 50 inches tall versus 40 inches tall. You’re probably going to go through the shorter cotton quicker with your picker and make up ground. We’re always trying to make up ground in the fall because we know, at some point, rain is coming.”

Dodds received the first picture of a cracked boll in the state two days earlier. “That can relate to irrigation management. Historically, when we’re watering down the row and talk about cutting water off is when the first cracked boll shows up. With pivots, it’s a bit later just because of the amount of water being delivered.

“This year, because of the rains, we may not need to water again. I hope we don’t. Some of the rains we’ve had were advantageous. It’s been a pretty decent year for us.”

As producers near the decision to knock leaves off the crop, “I encourage you to walk into the field and pull some plants back. What I feel tends to happen is some drive by in the truck and look to see how much cotton is actually open in the field. I feel we tend to underestimate how much is actually open in the field. A lot of times, we’re defoliating at 70 to 80 percent open thinking it’s 50 to 60 percent…

“Walk out into the crop, make a few counts. If you’re 50 to 60 percent open, I’d go ahead and get the leaves off the crop. … Always carry a sharp knife in your pocket. Go to the uppermost boll you think will be in the picker and cut it. If you see well-formed cotyledons, dark seed coats, not a lot of wet-looking lint, it’s probably ready to go.”

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