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Making adjuvants add up

Row-crop growers who add the correct adjuvant to their herbicide program this season can expect a $6 to $10/acre return on their investment, according to Southern Illinois University (SIU) research. The key word in this equation is “correct.” By nearly anyone's standards, adjuvant selection can be a confusing challenge, especially as new products enter the marketplace.

“Penciling a return on adjuvant use is sometimes difficult, but using the right one provides good insurance and a payoff,” says Bryan Young, SIU weed control specialist.

One dollar per acre is a typical investment for an adjuvant, although some of the top-end products cost up to $2.50 an acre. Newer adjuvants entering the marketplace for 2004 range from ammonium sulfate (AMS) replacement products to defoamers and herbicide/adjuvant markers.

“We used to have just a few classes of these products, but now we're breaking those classes down further to fit very specific needs. They're essentially what I refer to as designer adjuvants,” says Chris Stickler, manager of technical services and product support for Loveland Products.

Glyphosate driver

In most cases, the common denominator in new adjuvant product development is growers' ever-increasing use of glyphosate-based herbicides.

“That's certainly been my observation during the past two years,” Young says. “Most of the products introduced as new have been primarily modifications to products to make them more compatible with glyphosate.”

Bob Herzfeld, adjuvant business manager for Agriliance, estimates that 90% of postemergence herbicides on the market, such as glyphosate, call for the use of an adjuvant. However, only 60 to 70% of growers actually use one. That includes AMS, he notes.

The reasons some growers still don't use such products are that many still doubt whether adjuvant use provides a financial payoff, despite research confirming that fact; some are put off by the sheer number of products to choose from; and others are simply not aware of them and the benefits they offer.

Young manages an online informational tool, Compendium of Herbicide Adjuvants, which can help growers cut through company hype and determine if an adjuvant will help meet their weed-control needs. The site, which is updated annually, details nearly 450 adjuvant entries from 36 companies and is located at By accessing the site, growers can find product labels, adjuvant names and categories, manufacturer contact names and phone numbers, and even a glossary of terms.

Taking the first step

As with most other endeavors, education is paramount to success with adjuvants, and the information is available. “Read the label, and know what you're getting,” says Kent Woodall, director of marketing for Rosen's, based in Liberty, MO. “It takes a little effort, but you can be an educated buyer.”

Herzfeld advises, “Talk with your dealer about your options, look at independent research results, call suppliers and put side-by-side comparisons of at least one pass in your fields to assess results.” Such effort this year, he adds, will set you up for more success the next growing season.

Other advice from Herzfeld, Stickler and Woodall involves prepay herbicide dollars. “Know where they're going to be invested,” Woodall says.

Stickler says, “Retailers sometimes have a tough time relating the importance of adjuvant usage with prepay dollars. You inform the grower that he'll need to spend $15 to $20 an acre on a herbicide program. Then, oh, by the way, you'll need to add an adjuvant in there to help the product perform more effectively, which adds additional cost.” The result: Some dealers focus on the herbicide only during prepay and recommend the proper adjuvant closer to the time of application.

Plus, Herzfeld says, “a lot of dealers get bought in by program dollars rather than agronomic decisions. Growers need to assume responsibility, study about the products and call suppliers if they have questions.”

Replacing an old standby

Because of the extensive use of glyphosate-based herbicides, many companies are rushing to provide AMS replacement products to the market. Young says AMS historically has provided growers with two key benefits: It conditions hard water to minimize the potential negative impact from mineral deposits interacting with the herbicide, and it helps transport glyphosate across the surface membrane of the target weed, allowing for good coverage and plant uptake. Young's research, conducted on velvetleaf last year, shows that the addition of AMS in some instances is equivalent to increasing the glyphosate rate by one to four times. Although Young is not advocating that growers reduce glyphosate rates, he says the research demonstrates the one-two punch AMS delivers to help the delivery of glyphosate to weeds.

However, AMS is not without its challenges. For one, it is inconvenient to use. Stickler explains, “No one likes crawling up there [on top of a spray applicator] with a 51-lb. bag to dump into their tank. You'd much rather handle a 2.5-gal. jug.” In addition, AMS is time consuming to use; sometimes it clumps or hardens in the bag; and it takes up considerable storage space if not used promptly after its purchase.

Still, Young issues a challenge to suppliers marketing AMS replacement products: “They need to be all encompassing in their approach to what they're offering growers as a replacement. Not all AMS replacements add up to AMS.”

Herzfeld agrees. “You have to make sure your replacement product has enough ammonium ions in it to successfully transport the glyphosate,” he says. “Not every product does.”

Herzfeld says Agriliance worked diligently last year to show that its new product, Alliance, would stack up well compared with AMS. Alliance is a corn-based AMS replacement product formatted for high-load (premix) glyphosate-based herbicides. Herzfeld says that, sold in 2.5-gal. jugs, Alliance eliminates handling ammonium sulfate bags and minimizes the potential for sedimentation and nozzle plugging. He reports that Alliance was used on more than 2 million acres in its introductory year. More information on Alliance is available at

Helena Chemical Company introduces Strike Zone MxD. Designed to reduce drift and improve coverage, the product also is touted as an AMS replacement. It offers a crystalline composition that the company says mixes readily in water. More information is available at

Beyond glyphosate

Some companies, such as Rosen's, see the need to address adjuvant use for non-glyphosate-based herbicides. That's the case for its new product, Zenith, a surfactant system with AMS included. Zenith is labeled for use with non-glyphosate-based herbicides, such as Distinct and Northstar, and to improve product deposition, retention and plant uptake.

A new drift-control system called Shear Guard Technology is now available in Liberate, Valid, and Weather Gard products marketed by Loveland Products. According to Stickler, this new technology offers excellent drift control with minimal concern for pump shear or mixing issues. “Many drift-reduction agents are based on polymers that, after going through the pump, tend to break down and minimize their ability to reduce drift,” he says. More information about the Shear Guard Technology is available at


Glyphosate is notorious for foaming in the tank and causing application delays. To address this, Agriliance is introducing Foaminator Dry for the 2004 season. The product is sold in an 8-oz. container that Herzfeld describes as looking “like a parmesan cheese shaker.” He says one or two shakes of the container over the tank distributes sufficient product to result in an immediate reduction of foam. Foaminator Dry also is non-hydroscopic, meaning it does not harden but stays in its granular form.

Benchmark Foam HT is a new high-temperature-resistant foam marker from Kalo, based in Overland Park, KS ( It is targeted for postemergence herbicide applications and is formulated for successful results even in hard water.

Looking to the future

Manufacturers are beginning to offer more premixes to growers. Called high-load products, the term simply means manufacturers have combined the herbicide and adjuvant in one container. This can provide a time savings to growers while helping the manufacturer potentially maintain or increase market share.

Organosilicones, as an adjuvant component, offer another untapped market for suppliers and benefits that growers can reap at harvest, Stickler says. This class of products, used extensively in fungicide and insecticide applications in the European Union, allows for greater spreading ability of the spray droplets and, therefore, better coverage. Stickler notes that soybean aphid control in the United States represents one arena where organosilicones could be useful. Because this pest is generally distributed throughout the soybean canopy, any increase in coverage should improve control. The downside is that such products would cost growers between $0.50 and $0.75 more per acre.

Even so, Stickler says, “Quality adjuvants, used correctly, can greatly enhance pesticide activity, which results in a handsome return on the additional investment.”

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