“Be proactive and manage herbicide resistance before it becomes a major problem” was the main message delivered by Dr. Mike Owen, ISU Extension Crop Weed Specialist, during a field day Sept. 16 in Alexander, Iowa.
Diversity of tactics is key to consistent weed management and high crop yields. In fact, Dr. Owen says the correct management of weeds will make a farmer more money every year than managing any other pest complex. He should know. Dr. Owen has held his current position since 1982, and over the past 15 years, he’s placed even greater emphasis on studying herbicide resistance in weeds.
Owen says herbicide-resistant weed populations – especially common waterhemp, marestail and giant ragweed – are increasing in Iowa due to farmers’ management decisions. Because weeds are adaptable, Dr. Owens says it’s important to take these steps tosave the use of glyphosate herbicide for the future:
Use more than one tactic or herbicide to control weeds.
Use tank-mixes of herbicides with different modes of action (MOAs) that will control the weeds of concern. Tank mixes are better than rotation of MOAs.
Scout early in the spring and throughout the season. Weeds exist in un-tilled fields and will cost you money if you do not manage them prior to or immediately after planting.
Use a soil-applied residual herbicide on all acres regardless of crop or trait. Whether or not you plan to till the fields, include a residual herbicide that controls weeds that will germinate first, are most populous, and are of greatest concern.
Know what herbicides you are using, what they control (and do not control), what replant restrictions exist and if there is significant potential for crop injury.
Glyphosate has been called the world’s greatest herbicide because its overwhelming use and acceptance has made it the most widely used product on the market today. Dr. Stephen Powles, world-renowned expert on weed resistance, takes it one step further by saying that glyphosate is to weed control in agriculture as penicillin is to disease and infection treatment in medicine. Both are considered miracle products and given the distinction of being a “once-in-a-100 year discovery.”
So what can be done to help preserve the use of this wonderful chemistry? According to many weed scientists in the Upper Midwest, there are some basic steps that every farmer should take to prevent the onslaught of glyphosate-resistant weeds:
Know your weeds and know your fields. Closely monitor problem areas with tough-to-control weeds or what may be considered escapes or misses.
Start with clean fields. Use tillage, residual herbicides and/or burndown applications of herbicides to control all emerged weeds before planting.
Apply herbicides correctly. Proper application methods and rates are crucial to season-long control. The three most important factors are timing, timing and timing!
Control weed escapes. Because of the long-term ramifications of this problem, farmers can no longer be satisfied with “economic thresholds” of weed control.
Reduce the seed bank. Surviving weeds must not be allowed to set seed and thereby become the dominant weed species.
Clean equipment. Prevent the spread of these resistant weeds at all cost.
No single tactic will protect the potential crop yield nor deter the evolution of herbicide-resistant weed populations, said ISU Extension Crop Weed Specialist Mike Owen, in a blog article he posted earlier this season. Be proactive and manage herbicide resistance before it becomes a major problem. Diversity of tactics is the key to consistent weed management and high crop yields.
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