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Defoliate by weather, not calendar

That may mean adapting your tried and true cotton defoliation strategies to the crop conditions in each of your fields, according to Extension and research specialists around the Delta.

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

According to LSU AgCenter 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 says. “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 the Stoneville-based Snipes suggests using whatever approach has historically worked best 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, and growers should pay close attention to defoliation timing with high micronaire varieties,” Miller says.

“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,” says 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 (Finish or other ethephon containing products), ET, Harvade and Aim. “Tailored to the appropriate situation, these partners do a number of desirable things to assist growers in a successful harvest,” he says.

Cotton producer Will Pitts of Indianola, Miss., says, “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 says, “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,” says 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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