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12/20/2010 - 12/26/2010

New Information on Herbicide Labels

By Bob Hartzler, Department of Agronomy

Herbicide labels now include a standardized system to inform users of the product’s mechanism of action (MOA). A box labeled ‘Herbicide Group’ is present near the top of the label. The number in the box represents MOA of the active ingredient, based on a system developed by the Weed Science Society of America. Premixes containing more than one mode of action will have multiple numbers listed. Following is an example of the new logo.

The intent of this information is to simplify development of herbicide programs that reduce the likelihood of selecting herbicide resistant weeds. In production systems relying largely on herbicides for weed management, using herbicides with different MOAs is the primary means of managing resistance. 

Generally, the greater number of MOAs used, the less selection pressure placed on weeds.  However, designing an integrated program is not as simple as randomly adding MOAs. The different MOAs used in the program must have good activity on the important weeds in the field to successfully reduce selection pressure. Following are a few examples where the inclusion of an herbicide in a system relying on glyphosate in Roundup Ready crops would provide little benefit in terms of managing resistance for specific weeds.

• A Group 2 herbicide would provide little benefit for waterhemp since most waterhemp is resistant to these herbicides.
• A Group 15 herbicide would provide little benefit for giant ragweed or other large-seeded broadleaves due to its poor activity on these weeds.
• Tank-mixing low rates ( less than 0.75 lbs) of atrazine (Group 5) with glyphosate or other herbicides.

The new labeling system eliminates the need for farmers, consultants and suppliers to learn the MOA of all the active ingredients used in Iowa agriculture. However, to use the information properly, users must still know the activity of the individual herbicides on the weeds present in the field to insure that the target weeds are being affected by multiple MOAs.


Use this link to reach the Weed Science Society of America Mechanism of Action document.


Bob Hartzler is a professor of agronomy with extension, teaching and research responsibilities.

Iowa State Research Farm Reports Available to Public

By Mark Honeyman,  ISU Research Farms
There are fourteen Iowa State University Research and Demonstration Farms in Iowa; nine owned by associations (local farmers) and five owned by the university. One responsibility of Iowa State to the associations is to provide an annual farm progress report on the agricultural research and related scientific agriculture activities conducted at the farm as a year-end summary. Those reports, that were made available in the past to the members and others in print form, are now available online to the public at in a new format.

The report articles are organized on the website by research farm , university departments, broad research categories and more specific topic categories. These reports will be of interest not only to crop and livestock producers, but turf grass managers, home gardeners, and those involved in local foods, grape and wine, organics and vegetable production.

The farm report website has a binder feature that allows articles to be sorted, selected and saved as a collection. Once included in the “My Binder” feature, the articles are organized, given page numbers and a table of contents is created. The personalized collection of articles can then be saved to a personal computer and printed if desired.

Offering research results electronically puts the research articles in the hands of more people in an efficient way. Having the reports online helps fulfill the Iowa State University Extension mission by generating information and getting it to people who want it and can use it.

This article was published originally on 12/27/2010 The information contained within the article may or may not be up to date depending on when you are accessing the information.

Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.