Helping Late Cotton Finish Strong

By Larry Stalcup
beef2lar@suddenlink.net

China "I'm afraid we're going to need the whole season."

Those are Mark Appling's words to describe the finishing of his West Texas cotton crop. Like most cotton in the region, Appling's crop has faced, rain, more rain, cool weather ... and then even more rain over a freakish High Plains spring and summer. "We had received over 18 inches of rain by early July, and that's about our average for the year," says the Crosbyton, TX grower.

Appling and others in the region normally see the first bloom July 4-10, but it was the third and fourth weeks of July before that occurred this year. From about May 1 to mid-July, the crop received under 1,000 heat units, compared to over 1,300 for that same period in 2006.

Even if September and October see normal temperatures and rainfall, managing late cotton will likely require a new set of rules than were used in a dry 2006. In more than one incident, downpours "filled up the rain gauge and spilled over the top," says Dr. Randy Bowman, Texas Cooperative Extension cotton agronomist in Lubbock.
But he points out that even though the abnormally wet summer delayed a lot of cotton, it also helped growers cut back on irrigation needs and created the potential for a good dryland crop in the region.

Critical Decisions

"If growers want to obtain the best possible finish to their crop, harvest-aid selection will be critical," Bowman says, and he encourages growers to pay close attention to harvest-aid tank mixes, because late-season growth is very possible in the many picker varieties planted in the West Texas/Panhandle region this year. "Picker varieties can yield better and have higher quality fiber, but many typically mature later," he adds.

Late growth can be difficult to terminate with traditional applications of paraquat-based defoliants. Typically, desiccants - including Gramoxone Inteon, Firestorm and other tank mixes containing paraquat-based chemicals - are generally applied when 80% of productive bolls are open. That is usually 2-3 nodes above cracked boll. Paraquat applications generally work well to desiccate cotton with minimal juvenile growth.

However, Bowman says "protoporphyrinogen oxidase, or PPO inhibitor" defoliant compounds may be needed to help growers obtain a solid plant termination in some years. Newer PPO inhibitors include Blizzard, Aim 2EC, ET 2.5%EC and Resource. "These PPO inhibitors can shine when late rainfall and warm conditions result in juvenile growth."

Defoliants, which include Ginstar and Def/Folex, can be safely applied when 50%-60% of the bolls are open, and the remaining bolls are of sufficient maturity to obtain desired yield.

These defoliants should complement treatments of ethephon - "the backbone of our harvest aids," says Bowman. Ethephon is a boll opener, available in Prep and a growing number of generics. Generics include Ethephon 6, SuperBoll and Boll'd. Boll opener-defoliants include Finish 6 Pro and FirstPick, which are ethephon-based products with additional synergists, such as cyclanilide and AMADS, respectively, says Bowman.
Of course, the exact treatment will all depend on whether September and October are normal, or wet and cool. "We can expect to see some higher rates of ethephon in our late cotton," says Bowman. "But growers and consultants will have to consider various tank mix combinations, depending on the type of fall we have."

When boll openers and defoliants are used, a follow-up application - with paraquat or other product with desiccant activity - is often required to sufficiently condition the cotton for stripper harvest in the High Plains region.

"Although this adds more expense to the overall harvest-aid program, it is necessary in order to complete the season-long investment the producer has made," says Bowman.

Fiber Development
Bowman stresses that just because a harvest-aid program is used, it cannot increase fiber development in a crop.

"Harvest-aid chemicals cannot increase the rate of fiber development," he says. "Only additional good growing weather - including open skies and adequate heat units - combined with (the presence of) functional leaves, can mature cotton bolls."

Determining the maturity of a crop can be accomplished by using a sharp knife to cut into the bolls. "If the boll is watery or jelly-like on the inside, then it's immature and needs more heat units," says Bowman. "If boll development is to where the knife cannot slice through the lint, then the boll is nearly mature.

"Close inspection of the seed will give further indication of boll maturity. If the seed coat is turning tan and the seed leaves (or cotyledons) are fully developed, the boll is mature."