By Stevan Knezevic, UNL Weed Extension Specialist
Weed resistance to herbicides is not a new thing. It began to occur as soon as man started using chemicals for weed control. Weed scientists predicted in mid-1950s that repeated use of any herbicide could lead to shift in weed species, and that herbicide tolerance in weeds can increase with repeated use of the same herbicide. Very soon after that (early-1970s) the first cases of weed resistance occurred in pigweed species showing resistance to atrazine. There is well documented literature about weed resistance. Worldwide about 368 herbicide-resistant weed biotypes reported to be resistant to 19 different herbicide modes of action. For example, 40 dicot and 15 monocot species are known to have biotypes resistant to triazine herbicides. Also, at least 50 weed species have been reported to have biotypes resistant to one or more herbicide families (www.weedscience.com). Repeated use of the same herbicide was always the main reason for weed resistance to herbicides worldwide.  Therefore the main objective of this workshop is to educate agricultural clientele and farmers about the importance of herbicide mode of action, and how to use the Site of Action Numbering System to reduce potential for weed resistance in Nebraska.
Workshop will be offered at four locations, including: Kearney on January 23 (host Educator Brent Plugge); Scottsbluff on January 24 (host Educator Jim Schild); Columbus on January 28 (host Educator Allan Vyhnalek); and Beatrice on January 27 (host Educator Paul Hay). Registration might be limited to only 30 participants.
It is a minimum 3-hour long workshop, which will start with several topics for discussions, and then an active involvement of attendees. Topics for discussion will include: Herbicide Tolerant Crops, Herbicide Mode of Action and Site of Action Groupings, How Weed Resistance Develops, Weed resistance in Midwest and Nebraska. Attendees will also have a chance to conduct Hands-On Exercises on Weed Resistance Problems (eg. Waterhemp, Giant ragweed, and Kochia).
Workshops speakers are members of the UNL-Weed Science Panel, including: Bob Wilson, Amit Jhala, Lowell Sandell and Stevan Knezevic (lead). This Workshop is sponsored by the educational grant from the United Soybean Board. For more information contact host county educator, or myself (sknezevic2@unl.edu), or my secretary, Wendy Winstead (wwinstead2@unl.edu).  


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