PGRs Crucial In A Late Crop

08-13CFcvrBy Andrea Jones
Associate Extension Cotton Specialist
University of Missouri

This year cotton planting in Missouri got started around May 10; therefore, we have a late crop. Hopefully, by now we’re managing our crop for earliness and have planned for a timely harvest for our late planted crop.

Plant growth regulators (PGR) are a good management tool for earliness. Field history and weather should be considered when making PGR decisions. PGR typically help control plant height, increase leaf area and increase square and boll retention. As I like to say, “PGR helps the plant to put its energy into making fruit instead of getting too tall.”

In Missouri, many producers are applying the fourth plant bug application this week. Controlling plant bugs is also important to control growth. If fruit shed rates increase more, PGR is needed to set the fruit; however, if there is little shed, the plant needs to be bigger in order to hold the fruit.

Defoliation Is Important

After a full season of high-quality effort for good management, don’t mess up with poor defoliation at the end of the season. We must be sure to harvest as much of the crop as possible and produce the best quality possible.

There are four choices of defoliation timing:

• When 60 percent of the bolls in the field are open.
• When four nodes are above the uppermost harvestable boll.
• Using the COTMAN method of 850 DD60s after crop cutout.
• Using the Hal Lewis method.

Research at the University of Missouri shows the Hal Lewis method to be most profitable. This method is based upon the micronaire of the four bottom first position bolls. This defoliation method maximizes yield but also manages micronaire for more profit.

The method requires a table-top gin to gin the samples and a micronaire tester. Several consultants in the area have a gin and tester. For good defoliation, use 15 gallons of water or even more in order to get good coverage. A high volume of water may prevent having to make a second application where the crop is not too tall and rank.

During the time of defoliation is not an occasion to save money. Choose harvest-aid products based upon performance in order to maximize income. Good defoliation results in higher yields, better quality and ultimately more profit.

Contact Andrea Jones at the University of Missouri’s Delta Center in Portageville, Mo., at (573) 379-5431 or

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