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Glyphosate helpers

Johnnie Roberts is in the business of making herbicides work better. These days Roberts, the product development chemist at Helena Chemical, has been particularly focused on new adjuvant formulations for glyphosate. As the boom in Roundup clones continues, he sees a growing need for adjuvants that companies can add “in the can” or farmers can add “in the tank.”

The latest industry figures show that more than 40 differently named glyphosate products compete in the U.S. Already priced so low that few other products can compete, glyphosate now threatens to cannibalize its own market share, putting downward pressure on prices. But if you think it can't get any cheaper, look overseas.

Roberts points out that Australian farmers can buy glyphosate for even lower prices (nearly half the price paid in the U.S.) thanks to cheap supply from chemical plants in China and India. “That's good news for farmers, perhaps. But you won't get much technical service from a bargain-basement supplier selling on tight margin,” Roberts says. “And if the price goes too low, incentive for developing new and innovative glyphosate products might disappear as well. Higher pricing in the U.S. makes the development of more efficacious and easier-to-use products like Roundup Weathermax and Touchdown IQ more likely.”

Innovation and confusion

It's now an old joke in the chemical industry that the best adjuvant for glyphosate is more glyphosate. But the philosophy of “more is better” can only go so far. That's why chemists like Roberts continue to tweak and improve adjuvants and formulations. The current glyphosate market gives them little choice. “Few people realize it,” Roberts says, “but of all those seemingly unique glyphosate products out there, the majority of technical glyphosate used in the U.S. is sourced from one supplier, most often Monsanto. Improved adjuvants are the primary way to enhance performance and market to specific niches.”

Despite the dominant role of adjuvants, manufacturers continue to work on improving their glyphosate formulations. “Even though the active ingredient is the same in all glyphosate products, there are a number of different formulations based on different types of salts,” Roberts explains. “In many cases, these salts have an impact on things other than efficacy. Cold weather handling and spray mix compatibility, for example, can be different with each salt formulation. Farmers may see less foaming in the tank with some products.”

The EPA also recognizes the differences in active ingredients due to the different salt formulations, such as isopropylamine, potassium and ammonium. Some of the newer formulations pack more active ingredient per gallon.

Adjuvants are different

Roberts points to confusion with adjuvants as well. “Some farmers incorrectly interchange the words ‘surfactant’ and ‘adjuvant,’” he says. “A surfactant is just one type of adjuvant. Its primary function is to aid deposition, coverage and absorption of active ingredients. While some premium products include surfactants ‘in the can,’ they usually still require you to add additional adjuvants ‘in the tank.’ These might include drift reduction and deposition agents, liquid or dry ammonium sulfate [AMS], defoaming agents and marker foams.”

Helena, for example, offers more than a dozen categories of adjuvant products. In the entire industry, the last count for different adjuvant products being sold was 4,000 and growing.

No magic bullet

Although it's true that premium “high-load” glyphosates come with their own surfactant, not one of them can claim that you don't need to add adjuvants in the tank. At least not yet. “We know farmers prefer convenience and hate messing around with lots of tankmix components,” Roberts says. “The ultimate glyphosate product would be one that included all adjuvant functions [drift reduction, AMS, defoamer] in one can. Looking at the chemistry, we know it's possible. We just don't know how to do it yet without compatibility problems or having to use a high rate.”

Helena and other companies are getting closer to that ultimate goal. Some of their adjuvant products already perform multiple functions. They just can't be sold as a premix with glyphosate.

The right stuff

Bob Herzfeld, adjuvants business manager for Agriliance, says up to 70% of the effectiveness of a herbicide is driven by the adjuvant system, either when it is a tank additive or when it is part of the product formulation. “Choosing the right adjuvant to make your herbicide work can be complicated, especially when it comes to the growing number of glyphosate products on the market,” Herzfeld says.

He also emphasizes the importance of making the distinction between high-load and low-load glyphosate products. “A lot depends on which form of glyphosate you use,” he says. “It could be either a Weathermax or Ultramax, which we call a high-load. Or you might have a low-load and partial-load product such as Roundup Original or a private label Cornerstone.”

In simple terms, a low-load glyphosate has less stuff premixed into it. You have to add nonionic surfactants, and most growers also need to add something for drift control. High-load glyphosate products may still require adding AMS in the tank. Low-load products always require it.

Hard water

As new varieties of Roundup Ready (RR) soybeans move north, so goes glyphosate. But Herzfeld says that where the temperature is cold and the water is hard, the dry AMS product often won't dissolve well when you dump it in the tank. Sometimes it takes up to 35 minutes.

“Glyphosate is very sensitive to impurities in the water that can tie up the chemical,” Herzfeld says. AMS is cheap and readily available. But Herzfeld says handling those heavy bags adds up to a lot of work. “Liquid ammonium sulfate is a better option, but you typically need 2.5 to 5 gal./100 gal. in the tank. That's an awful lot of liquid to deal with,” he says.

Agriliance is bringing new adjuvant products to market that can reduce handling and volume for both high-load and low-load glyphosate products.

Big potential

In the Midwest, RR soybeans account for 70% of the market. Herzfeld says growth of glyphosate in corn could take off just as soybeans start to level off. “There's only so much market share to go around on beans,” he says. “But based on what I'm hearing in the field about Roundup Ready corn, I'd estimate up to 35% of corn acres could go to glyphosate in the next two years.”

That's not as big as the percentage for beans, but it's still a substantial amount. Additionally, Herzfeld sees potential for fallow acres in the West to rival soybean glyphosate acreage in the East. “Preharvest and postharvest burn down also could be a huge market for lower-priced low-load glyphosate herbicides,” he says.

If Herzfeld is right, the boom in glyphosate acreage isn't even close to leveling off. And competition among the various companies that sell it is going to get fierce. Although farmers can hope for price wars, it's also likely that each company will continue to pursue product differentiation and higher prices by adding different adjuvants.

Changing markets

“We're seeing several different markets emerge,” Herzfeld says. “And each will require a different adjuvant strategy.” In the Midwest, high-load premium products that are more forgiving of weather conditions will be popular on RR corn and soybeans.

“There also will be a growing need for drift control where you see RR crops next to conventional crops and suburban areas,” Herzfeld says. “Lower-priced low-load products will dominate in the West where burn down and fallow weed control are the objectives.”

Helena's Roberts anticipates a similar future. “We're seeing a couple of things happen to our adjuvants business that are a direct result of what's going on with the glyphosate market,” he says. “While surfactant sales decreased 20% in 2001, they came back a bit in 2002. Overall, almost 70% of our dealers reported an increase in adjuvant sales, with the biggest increases coming from drift control and AMS products.”

Volunteer corn

University researchers are already sounding an alarm about the idea of planting RR soybeans after RR corn. But as they worry about herbicide resistance, convenience-minded farmers are thinking more about how to control RR volunteer corn in RR beans.

Herzfeld leans more toward the farmer. “It's unrealistic to ask farmers to spend more money on herbicides when what they are doing now works,” he says. “The glyphosate resistance issue is real, but for most farmers it is not an urgent problem. The big issue that we see is that if you follow RR corn with RR soybeans, how are you going to control your volunteer RR corn in RR soybeans?”

Herzfeld points to products such as Select postemergence grass herbicide that can be tank mixed with glyphosate to take both weeds and volunteer corn out at the same time. But he says adjuvant choice gets trickier when you start mixing herbicide modes of action.

“Normally, Select needs a methylated seed oil or a crop oil,” Herzfeld says. “But if you add crop oil or methylated seed oil to that tankmix with Roundup, you lose your grass control from the glyphosate.

“If you go with too low of an adjuvant system, too weak of a rate of an nonionic surfactant, you lose your volunteer corn control from the Select,” Herzfeld continues. “So you have to balance that adjuvant system to get the most out of both components. This is a problem we hope to solve with a new adjuvant system that will enhance both herbicides in the same tankmix. We expect to have an adjuvant that complements both glyphosate and Select in test market by next year.”

Are glyphosate salts the same?

Farmers may remember last season's war of words between Monsanto and Syngenta about whose formulation of glyphosate is better. The argument lost some of its thunder when Iowa State University researcher Bob Hartzler weighed in to say that no third-party research could confirm any difference between Roundup Ultra and Touchdown IQ. Statements from other university people support Hartzler's position. Below is a summary of points made in “Sorting Through the Glyphosate Jungle,” a paper by Alan York of North Carolina State University


Touchdown 5, formulated as a trimethylsulfonium salt, is primarily a burn-down product. It was also registered for application to Roundup Ready soybeans. There was minor injury (basically chlorosis or foliar burn) to the soybeans, but the effect was only cosmetic. This response was due to the trimethylsulfonium salt, not the active portion of the molecule. Touchdown 5 was not registered for postemergence application to Roundup Ready cotton or corn because these crops were much more severely damaged by the trimethylsulfonium salt.

The new Touchdown IQ, introduced in 2001, is formulated as a diammonium salt. University research has shown little or no difference in response of weeds, Roundup Ready corn, cotton or soybeans to Touchdown IQ and the various brands containing the isopropylamine salt of glyphosate.

The salt is held to the glyphosate molecule by weak bonds. Because of this, once the product is added to the spray tank, the salt ion is easily dissociated from the glyphosate parent molecule. Thus, the glyphosate that reaches the leaf surface is often not associated with the salt it was formulated with. Weeds really don't know the difference among the various brands and salt formulations.

Differences in weed control with the various products, if observed, are much more likely to be caused by differences in the adjuvants included in the formulated products rather than the salt used in the formulation.

Read the full text of York's paper at

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