Touchdown or Roundup? About every form of ag media has featured stories and advertising “for” and “against” both herbicides.

Texas cotton grower Jackie Warren has heard and read them all, like most other farmers. He's a firm believer in Roundup Ready cotton and formulations of Roundup herbicide. Yet Warren decided to see for himself if a new product, Syngenta's Touchdown IQ, was comparable to Roundup UltraMax, the newest from Monsanto's Roundup Ultra family.

His tests on 640 acres of irrigated cotton showed excellent weed burndown in both cases, with no harm to cotton plants.

Warren farms primarily no-till cotton and peanuts near the west Texas city of Lamesa. He and his family have about 5,000 acres of dryland cotton that averages ½-¾ bales in yield, and about 800 acres of center-pivot irrigation that produces 1½-3 bales/acre, depending on water availability.

He's grown Roundup Ready cotton since it hit the market in 1996 and '97. And applications of the herbicide over-the-top and via banding have provided the weed control he needed. The days of hoeing crews are now mostly in the past, or mainly for escape weeds.

Why try Touchdown? It wasn't because he was dissatisfied with Roundup formulations. “I just feel like competition is healthy for our industry,” he explains. His decision to test Touchdown IQ, first labeled for cotton in 2000, came after he saw research results from trials through the Texas Agricultural Experiment Station (TAES) in Lubbock. He also received a guarantee from his Syngenta representative.

“I felt like we had a fair test,” says Warren. “We treated half the pivot circles with Roundup UltraMax and half with Touchdown IQ at the labeled amounts. I saw equal results in weed burndown. I saw no negative effect to the cotton plant.”

His results were similar to those from the TAES 2000 research, headed by weed scientist Wayne Keeling. Keeling and his associates compared Touchdown to Roundup Ultra in several separate studies. Applications were mostly ¾ lb/acre at both the two-leaf and four-leaf stage. The plots were evaluated for weed control and crop damage on June 22, 2000, and July 3, 2000.

In nearly every case, Touchdown provided 100% control against pigweed and devil's claw, two weeds common to cotton in the region. Roundup Ultra showed virtually the same results. There was no injury to the cotton from either herbicide. Yields were also similar for plants that received a preplant irrigation in a dry, hot year.

“These tests show that Touchdown provides similar weed control to Roundup Ultra,” says John Everitt, who, along with LeAnna Lyon, is a research associate assisting Keeling in the weed control studies. “We looked at about a dozen plots and saw no differences in weed control.”

In normal field use, both herbicides can be applied twice over the top of Roundup Ready cotton. The two applications, however, must be at least 10 days apart; two nodes of new growth must have shown between applications; and the second application should be made before cotton exceeds the four-leaf stage.

Results from 2001 research on Touchdown, Roundup Ultra and Roundup UltraMax are still being read. But the researchers feel they will again see similar findings.

What's the difference? Both Touchdown and Roundup Ultra are registered brands of glyphosate. The difference is in the exact chemical makeup, says Randy Boman, Texas A&M cotton agronomist in Lubbock.

“Both herbicides contain the same active ingredient, only the salt formulation and surfactants are different. Roundup Ultra is an isopropylamine salt of N-phosphonomethyl glycine. Touchdown IQ is a diammonium salt,” says Boman.

He points out that there was early confusion about whether Touchdown IQ was legal for cotton. “Touchdown 5, which is yet another different salt formation (trimethylsulfonium, or TMS), was never labeled for Roundup Ready cotton,” says Boman. “Touchdown IQ, however, is labeled for cotton. And the herbicide differences between it and Roundup Ultra are generally very minimal.”

Warren says the cost of Touchdown in bulk, about $35.50/gallon, was a little cheaper than Roundup UltraMax, which was about $44.50/gallon. Roundup UltraMax has a more elaborate replacement incentive package than Touchdown. Both are well worth the application expense of $3.50-4.50/acre in a band-on application for dryland cotton, or $10-14 for solid broadcast applications on irrigated, he says. That's especially true when compared to a hoeing crew that costs $15-30/acre.

“I'm still considering whether to continue using Touchdown in the long run. One year's results are not enough to determine whether we will use it,” says Warren. “But if it continues to look good, and I have a guarantee, that takes a lot of the fear out of whether I use it instead of a product like Roundup.”

For further information on Touchdown, visit the Syngenta Web site at www.syngentacropprotection-us.com. More information about the Roundup formulations is available at www.farmsource.com/product_info/default.asp.