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The 2009 ASHS Annual Conference

Managing Weeds with Reduced Herbicide Inputs

Monday, July 27, 2009: 4:50 PM
Laclede (Millennium Hotel St. Louis)
Harlene M. Hatterman-Valenti, Plant Sciences Department, North Dakota State University, Fargo, ND
Many researchers have coined terms such as sustainable production, natural systems agriculture, organic production, and pesticide free production to describe methods that alter what we have come to know as conventional production.  Most have reduced or eliminated one or more inputs in a production process.  Some have eliminated synthetic inputs in an attempt to mimic a natural system.  However, all have the goal to develop an environmental and economical production practice for producers.  The same can be said for weed management.  Researchers continue to assess alternative methods for weed control with the goal that these methods are viable both environmentally and economically.  Most of these methods require increased management: specific weed assessment, understanding economic thresholds, knowing the critical period for control; knowing the competitiveness of the crop; and understanding an herbicide’s biologically effective dosage.  These factors were all considered when investigating onion weed management strategies.  Incorporating the micro-rate technology developed for weed management in sugarbeet worked well because both crops had similar characteristics during the early stages of growth and development.  Both crops are also more prone to herbicide injury during and shortly after emergence, than later growth stages.  Lastly, both crops had post-emergence herbicides registered for use.  Micro-rate technology takes advantage of differential metabolism between the target weeds and the crop.  Thus, the onion seedlings metabolize or inactivate the herbicides faster than the target weeds so that by the second herbicide application, the targeted weeds continue to accumulate the active herbicide in their systems. The subsequent applications increase the activity of the herbicide in the weeds resulting in improved control without increased crop injury.  Utilizing the micro-rate technology, we have been able to develop a weed management strategy that not only reduces the amount of herbicide used each season; it also improved weed control during the critical period for control.