Culpepper said just two plants per 20 foot of row can reduce yield by 23 percent. “It’s also a harvest efficiency disaster.”

He said cotton farmers have to learn how to control seed production from Palmer amaranth “or get out of cotton. A female plant produces a lot of seed, 300,000 to 500,000 per year. With that production, you only need one or two years before the weed becomes impossible to control economically. I prefer to get it in year one.”

He said plants also spread with pollen movement.

Culpepper said that even with excellent control as high as 99 percent, resistant Palmer amaranth seed production “will overwhelm us. We can’t do better than 99 percent.”

Ignite can be effective but has to be applied on a timely basis. If not, plants may be just stunted and will come back. “If you don’t get it the first time with Ignite, you probably will not,” he said.

So far, Texas has avoided the devastating resistance problems that have hammered Southeast and Mid-South cotton fields, but Culpepper recommends caution.

“Texas cotton farmers should accept the seriousness of the situation,” he said. “Georgia farmers took four years and now they are trying to catch up. Listen to your weed control specialists.”

He advises farmers to “pounce on small areas in a field” where suspected resistant weeds show up. “Pull them up. Don’t let them go to seed.

“Don’t expect new chemistry to save you. That’s not the answer. New ones will help but it will still take an aggressive program with Palmer amaranth. Rotate chemistry and develop integrated programs.”

Deep tillage

He said deep tillage may be a key. Palmer amaranth emerges from a shallow depth, he said, and seed life is not as long as once thought. “Seed require a lot of light to emerge so deep tillage, putting the weed seed 4 inches deep, will help.

“Make smart decisions over the next few years.”

Culpepper said “not one acre of Georgia cotton will be planted without an incorporated herbicide in 2010.

“We’re also using hooded sprayers. We can tank-mix Roundup and Diuron or Caparol. Every acre in the state will get a directed spray or hooded sprayer application,” he said.

Culpepper did a little math exercise to show how fast the problem can develop into a nightmare.

The first year, consider that five Palmer amaranth female plants escape and produce 2 million seed, of which 50 percent germinate. The following year an aggressive weed control program takes out 99 percent of the Palmer amaranth population, leaving 1,000 plants at harvest and 400 of them female. That means 160 million seed, which, at 50 percent germination, leaves 80 million.

Assuming another aggressive weed control program and another 99 percent success rate, 80,000 plants survive the next year, with 50 percent germination.

The next generation would be 1.28 multiplied by 10 to the tenth power, which equals – disaster.

rsmith@farmpress.com