THEY SAY cotton defoliation is as much an art as a science. But that doesn't mean a little science won't help. PPO-inhibitors came on the market as cotton defoliants three years ago. Aim was the first to arrive. Then, ET was introduced last year.

The defoliants work by inhibiting photosynthesis and have given cotton growers yet another item to include in their tank mixes.

Right now, growers can choose between defoliants, desiccants, harvest aids, and boll openers. Each has a specific use, and the conditions that growers face are so diverse that the art of defoliation varies across the Cotton Belt.

“Cotton defoliation varies so much across regions. One tank mix or one system might work great in one area, but not so great in another,” says Jack McDaniel, technical sales rep for Nichino America. “It varies state by state, even county by county.”

In the Delta, growers hope to defoliate in one pass, but often have to go back a second time to clean up a field. Other growers simply go into defoliation expecting to make that second pass and incorporate it into their plans, says Charles Snipes, project coordinator for the Cotton Defoliation Work Group at Mississippi State University.

Snipes has had ET in his Beltwide trials the past two years. “I like it sequentially and especially as a second application if a grower needs to clean up his fields,” reports Snipes.

“ET seems to work best with Dropp, but it can also be mixed with Def or ethephon. If you want your bolls opened, you could tank-mix ET with ethephon, followed by ET alone. If you want to control regrowth, you could tank-mix it with Dropp, followed by ET alone.”

“PPO-inhibitors are good for drying leaves quickly and still obtaining a rapid and acceptable defoliation,” says Billy Warrick, Extension agronomist at Texas A&M University. “They make a good tank-mix partner, and both Aim and ET are good at controlling regrowth. That means a lot to growers here.”

Before Aim and ET, cotton growers in the Delta would typically use Dropp, followed by sodium chlorate and paraquat, says Snipes. “The PPO-inhibitors do as good a job as sodium chlorate and paraquat and are priced comparably, plus you're talking ounces per acre versus gallons,” says Snipes. “It used to be 1.5 gallons of sodium chlorate and a few ounces of paraquat per acre, and that gets to be a lot of material to handle over a large area.”

ET was available in limited quantities in its first season of production, but will be fully available in 2004.

“We had a hard time getting hold of ET last year,” says Snipes. “A lot of people wanted to try it and couldn't get it. I'm sure they'll be looking for it this year.”