No. 3 Article 6/April 8, 2005

Proliferation of Premix Products

It's no secret that while the introduction of novel herbicide active ingredients has slowed (i.e., reduced some inventory problems) recently, a plethora of premix packages has proliferated (i.e., added some inventory challenges). For the past several years, we have published an article in the Bulletin that describes herbicide premix products that are commercially available for corn and soybean production systems, and we continue again this year. The basic text hasn't changed much over time, and we hope it remains useful to our readers.

Updated tables of corn and soybean premixes always accompany the article and are described in detail within the following text. One limitation of the tables is that a single application rate of each product is presented, with product active ingredients and equivalents calculated based on that rate. If you would like to know product active ingredients and equivalents for a rate different than the one presented, the text provides examples of how to do the calculations. We are working on an online herbicide premix calculator, where you can input your rate of interest and the calculator will determine all active ingredient application rates and product equivalents. When finished, this calculator will be accessible at the University of Illinois weed science Web site.

Herbicide premixes can often be confusing with respect to components, product equivalents, application rates, and so on. Table 1 lists many of the corn herbicide premixes used in Illinois, while Table 2 is a similar list of soybean herbicide premixes. Let's examine the information in these tables in a little more detail.

The first column lists the commercial or trade name of the herbicide and its formulation. The commercial or trade name is the name most familiar to folks. Another list of names (arguably less familiar than the names in the first column) appears in the second column; these are the common names for each herbicide component of a premix. For example, in Table 1 we see that Axiom (trade name) 68DF (formulation) is composed of the active ingredients flufenacet (common name) and metribuzin (common name). Common names are useful because they always refer to the same active ingredient; trade names don't always refer to the same active ingredient.

Think back a few years to a herbicide with the trade name Option. This product contained the active ingredient fenoxaprop (common name) and was used for postemergence control of grass species in soybean. The Option (trade name) herbicide now on the market contains foramsulfuron (common name) and is used for postemergence control of grass species in corn. Needless to say, you don't want to apply fenoxaprop to corn or foramsulfuron to soybeans, hence the benefit of knowing herbicide common names.

The second column also provides the amount of active ingredient or acid equivalent of each component per gallon or pound of formulated product.

The third column lists an application rate for each premix. We tried to select application rates that were representative for Illinois, but you may want to select a different rate and redo the calculations in the fourth and fifth columns. The fourth column indicates how much of each active ingredient is applied at the rate listed in the third column. Going back to the example of Axiom, we see that 19 ounces of Axiom provides 0.646 pounds of flufenacet active ingredient and 0.162 pounds of metribuzin active ingredient. Note here that while rates of commercial products are usually expressed in ounces, pounds, pints, quarts, and so on of product per acre, active ingredients are usually expressed in units of pounds of active ingredient or acid equivalent per acre.

Finally, the last column lists product equivalents for each premix component when applied at the rate listed in the third column. So the 19-ounce rate of Axiom provides the same amount of flufenacet and metribuzin that is contained in 17.23 ounces of Define 60DF and 3.45 ounces of Sencor 75DF, respectively.

The application rates listed in the tables are meant to be used as a reference. For some of these herbicides the application rates will vary depending on soil texture, organic matter, weed species and size, and such. Always consult the respective herbicide label for appropriate application rates. If you are interested in a rate different from that listed for a particular herbicide, it's relatively simple to do the calculations for your rate of choice. We'll work through an example to make it a little easier to understand.

The application rate of Harness Xtra 5.6L listed in Table 1 is 2.5 quarts per acre. Instead of 2.5 quarts, you want to know how much acetochlor and atrazine are applied at a 2-quart rate of Harness Xtra 5.6L.

--Aaron Hager and Dawn Nordby

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