There were many corn and soybean fields with prominent patches of giant or common ragweed, common waterhemp or volunteer corn during my travels in Minnesota, Wisconsin and Iowa this fall. These weed patches were likely the product of glyphosate herbicide overuse.
Now is the time to develop a plan and take control of herbicide-resistant weeds before they take control of you. Due to the long-term exposure to glyphosate in the corn and soybean cropping system, we are now in a situation where the probability of finding a glyphosate-resistant giant or common ragweed or waterhemp is high.
Currently, glyphosate-resistant weeds are a serious problem in the southern U.S., resulting in significant increases in herbicide and labor costs, and increased field applications. The situation isn’t as dire in the Upper Midwest now, but the trend with herbicide-resistant weed development in a field is a slow start that can grow exponentially by the next season.
To proactively address glyphosate-resistant weeds, you must reduce your total reliance on glyphosate and diversify your weed-management practices, with more emphasis on spring and early summer weed control and a more focused use of glyphosate in the crop where its weed control is of greatest value to you.
The following strategies are recommended by Extension Specialist Jeff Gunsolus based on experience and extensive research conducted by University of Minnesota Extension and other land-grant institutions:
In all fields:
In fields currently infested with glyphosate-resistant weeds
For more educational resources on crops production in Minnesota, visit University of Minnesota Extension’s crops website.