Touchdown looks good in weed tests

An analysis of the year 2000 weed control trials in Roundup Ready (RR) soybeans, RR corn and RR cotton, shows that new Touchdown herbicide with IQ Technology was a consistent performer when compared to Roundup Ultra and Roundup UltraMax herbicides.

The trials, performed by university and Syngenta researchers, indicated that new Touchdown delivered better weed control than Roundup 42 percent of the time; Roundup Ultra or UltraMax was better 30 percent of the time; and the competing products performed equally well 28 percent of the time.

The consistent performance edge can be especially important over the long-haul on diverse weed populations, said Chuck Foresman, technical brand manager for Syngenta Crop Protection, Inc. It could mean the difference between good results and great results.

“The performance gap was especially pronounced on certain tough weeds, for example, morningglory, pigweed and velvetleaf,” said Foresman. The following patterns emerged:

On morningglory, Touchdown out-performed Roundup 69 percent of the time, while Roundup Ultra or Roundup UltraMax was better just 25 percent of the time.

On pigweed, Touchdown was more effective in 52 percent of the trials, while Roundup was better 29 percent of the time.

On velvetleaf, Touchdown was the top performer 42 percent of the time, while Roundup Ultra or UltraMax took the lead 35 percent of the time.

The maximum level of yellow flash — crop response to over-the-top applications in RR soybeans — was 50 percent higher with Roundup compared to new Touchdown.“Obviously, these are both excellent herbicides,” Foresman said. “But trends found in the data show that the differences between Touchdown and regular glyphosate products like Roundup will show up in consistency of weed control.”

At Colorado State University in Ft. Collins, Colo., weed scientist Phillip Westra also saw significant differences between Touchdown and Roundup Ultra when the two herbicides were compared head-to-head in RR beans, without ammonium sulfate.

“When you looked at the two products by themselves, the new Touchdown was definitely more effective on the weed spectrum we looked at,” Westra said. Touchdown controlled 95.7 percent of the kochia in a RR soybean trial vs. 85 percent control for Roundup Ultra; Touchdown gave 100 percent control of pigweed vs. 90 percent by Roundup Ultra; and on hairy nightshade, the score was 98 percent control by Touchdown vs. 93.3 percent by Roundup Ultra.

“When you consider that many growers have been adding ammonium sulfate to enhance the activity of glyphosate herbicides for years, it makes perfect sense to start with diammonium glyphosate as the basis of Touchdown.”

Added Tim D'Amato, Westra's research associate who managed the trials, “We found that without ammonium sulfate, Touchdown was actually doing a little better job than Roundup Ultra — it burned down weeds a little quicker and a little more completely.” Though the differences weren't enormous, they were significant, D'Amato said, and the same pattern emerged when the two herbicides were tested on larger weeds a week later.

The difference, Foresman explained, starts with the glyphosate molecule itself. Roundup and generic glyphosate herbicides contain glyphosate isopropylamine (IPA), while the active ingredient in Touchdown is diammonium glyphosate (DA). Foresman said diammonium glyphosate is readily taken into treated weed tissue, and the ammonium molecule makes the cell membranes of treated weed tissue more permeable to glyphosate. Recognizing the importance of ammonium, the company's scientists linked it directly to the glyphosate molecule by creating diammonium glyphosate.

“When you consider that many growers have been adding ammonium sulfate to enhance the activity of glyphosate herbicides for years, it makes perfect sense to start with diammonium glyphosate as the basis of Touchdown,” he noted.

The diammonium glyphosate active ingredient is combined in new Touchdown with a corn-based, balanced adjuvant delivery system in a patented formulation Syngenta dubbed IQ Technology, said Foresman. Syngenta researchers tailored a blend of adjuvants to optimize uptake and movement within treated weeds, while minimizing crop response.

Westra noted that formulations can make a big difference in herbicide performance. “They can have a variety of effects, to increase the speed of uptake or enhance the amount of uptake. More of the material gets into the plant,” he said. “The Touchdown formulation chemists did a very good job.”

Knowing that a herbicide can give you an edge more often than not — that it consistently outperforms another herbicide — can be especially important in seasons where there's little margin for error, said Westra.

“It's real important in our environment, where weeds can be stressed,” he said. “They develop a thick cuticle because of hot, dry conditions. Also, if there are a lot of weeds competing, you might not get full coverage. Having a slightly more effective product in those cases can make a significant difference.

“We'd be hard-pressed to say right now that Touchdown is far superior, but these subtle differences are important,” said Westra. “Glyphosate is probably the single most widely used herbicide in the world. Anything we can do — even if it's just a one or two percent increase — is going to have a huge impact on weed control. This new Touchdown represents a step in that direction of more efficient weed control.”

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