Match defoliation to crop condition

If there's one thing producers will remember about the 2003 cotton crop it's the extreme variability of crop maturity and crop conditions from one area of the Cotton Belt to another, and even from one field to the next.

That required adapting tried and true cotton defoliation strategies to the crop conditions in each field.

Cotton specialist Charles Snipes at the Delta Research and Extension Center in Stoneville, Miss., said that because of crop variability this year he suggests growers take an average boll opening across the field. “Your average should be 60 percent open bolls across the field, with at least 40 percent open bolls minimum in greener areas of the field.

“We'd be in a three-bale area if we could keep half of the fruiting squares we lose every year,” he said.

According to Louisiana weed scientist Donnie Miller, research in that state has shown that maximum yields are possible when defoliants are applied anywhere from 42 to 81 percent open bolls, depending on crop maturity and fruit distribution.

“Depending on fruit distribution on the plant, maximum yield can be obtained when defoliation occurs prior to 60 percent open bolls,” he said. “In cases where a large fruiting gap occurs and a large percentage of bolls are less mature and set in the uppermost region of the plant, optimum defoliation timing may occur later than 70 percent open bolls.”

Deciding which harvest aid products to use can seem tricky, but Snipes suggests using whatever approach has worked best in past years on your farm, tailored to the given situation.

Miller agrees, saying, “There is no one-size-fits-all recommendation for cotton defoliation.”

Each different harvest-aid treatment has its merits and limitations, with proper timing critical no matter which product is used to do the job. Make your harvest-aid application too early and you could end up with reduced efficacy and yield. Delay your defoliation treatment too long, and you could see decreased lint quality, high micronaire values, and reduced efficacy because of cooler temperatures.

“In 2002, 51 percent of the Louisiana crop was discounted for high micronaire. Some of these discounts can rightfully be blamed on delayed defoliation. Growers should pay close attention to defoliation timing with high-micronaire varieties,” Miller said.

“Dropp or FreeFall certainly is a good choice if the hot, dry weather conditions we're experiencing continue. At a rate of one-to-eight, Dropp/FreeFall in combination with crop oil concentrate and ammonium sulfate is a cheap $10 treatment that works really well under present conditions,” said Snipes. “If you get good coverage, it does a nice job.”

Snipes recommends tank-mixing Dropp or FreeFall with another defoliant if the situation warrants or conditions become less favorable for Dropp activity. Good choices for tank-mix partners with Dropp or FreeFall include Def, ethephon (or ethephon containing product), Harvade, ET and Aim. “Tailored to the appropriate situation, these do a number of desirable things to assist growers in a successful harvest,” he said.

Cotton producer Will Pitts of Indianola, Miss., said, “In this day, when you are putting 10,000 acres on a picker, we can't afford to scrap. At one-to-eight, Dropp held pretty well for us last year, even through two hurricanes.”

For those growers faced with removing plant regrowth, Snipes said, “Ginstar at a rate of 1-to-30 is the preferred treatment, but paraquat, ET and Aim do a good job as well.”

“Crop and weather conditions drive how much time is needed between making a harvest aid application and driving your cotton picker into the field to begin harvest. They always have and they always will,” said Snipes. “Don't let anyone tell you that you can put a product out and count on harvesting 10 days later.”

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