Diversity of Tactics is Key to Weed Management

“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 to save 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.