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Heat units help can determine usefulness of pest treatment

Several steps leading to harvest are based on the of heat units after cutout.

First in a series of video from the 2021 University of Arkansas Cotton and Rice Field Day

When it comes to preparing a cotton crop for harvest, follow the research data, according to two University of Arkansas System Division of Agriculture Extension cotton specialists who spoke during a presentation at its virtual Corn and Cotton Field Day.

Dr. Bill Robertson and Ray Benson say it’s easy for growers to begin second-guessing their decision to terminate control of plant bugs in cotton, for example, after the recommended cutoff date of 250 heat units after nodes above white flower five.

Robertson, state Extension cotton specialist, and Benson, Extension staff chairman for Mississippi County in the northeast corner of Arkansas, were speakers for two sessions of the University’s Corn and Cotton Field Day, which was held virtually again this year due to Covid-19 pandemic concerns.

See more: Terminating irrigation may require multiple tools

Several steps leading to defoliating and then harvesting the cotton crop are based on the number of DD-60s or heat units after cutout, which is defined as when nodes above the highest white flower equal five.

“Our recommendations are 250 heat units after cutout or nodes above white flower five if the field is relatively clean of plant bugs, then we can stop worrying about them,” said Benson. “The thing people need to keep in mind is the plant is going to continue to grow and put young fruit on. And it’s going to attract plant bugs. You’re going to see a lot of them.”

“But that fruit’s not going to be making us money?” said Robertson. “Those aren’t the money bolls.”

“Correct – And in some ways it can attract them away from fruit that you can harvest,” said Benson. “So the visual appearance of all the insects you can see after this point, if you’re not careful, can make you second guess.

Solid research

“But I don’t know that we have tested anything anymore than this before. It’s got a solid research base, and I have all the confidence in it.”

“Dr. Rogers Leonard (former professor of entomology with the LSU AgCenter in Baton Rouge, La.) and others in the Southeast have looked at the termination of in sect sprays for plant bugs,” said Robertson. “And a lot of times they did that in a cage study where that was the only fruit they had the opportunity to feed on. Everybody’s really comfortable with 250, aren’t they.”

“Yes, they are,” said Benson.

“When you go in a field that’s 450 to 500 heat units after cutout, and you see plant bugs out there, they may be more friend than foe because they’re knocking off some of that fruit that is stealing energy from the bolls that are going to be making you money,” said Robertson.

He said that when growers observe cutout or the appearance of the last bolls that can make them money, they can visit GrowDegreeCalc.uada.edu and look at the number of heat units that are accumulating on a daily basis.

“We can look at that or information that is distributed by Arkansas Extension Specialist Amanda Free and determine when we’re 250 heat units past cutout,” said Robertson.

To learn more about cutout in cotton, visit https://www.cotton.org/journal/2001-05/1/upload/jcs05-001.pdf.

Next: Phantom bolls can cost growers real money

TAGS: Insects
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