Why You Don’t Want Glyphosate-Resistant Giant Ragweed in Your Fields…

A recent study conducted by researchers at Purdue University explains one reason proactive resistance management can be worth it.

In the study, giant ragweed was planted into corn at a low density.  Since the effects of giant ragweed competition for water and sunlight are already well-documented, this particular study focused on the effects of nitrogen competition.  The study found that even in a low density population, giant ragweed is still highly competitive with corn for nitrogen.  In fact, the study found that when the giant ragweed was not eradicated during the season, it reduced the corn yield by 19 percent.

With corn currently being such a valuable crop, a 19 percent yield reduction translates to a significant loss. While this study emphasizes the need to control weeds early to preserve yield potential, it also demonstrates the need for options to control difficult weeds. Glyphosate-resistant giant ragweed continues to spread to more counties in Indiana and Ohio. ALS-resistant giant ragweed is also widespread. With each new case of resistance, fewer options become viable, reinforcing the need for a multi-faceted management approach. And, the need to preserve the technologies we currently have available. 

This technical bulletin offers further management recommendations for glyphosate-resistant giant ragweed.  Additionally, Purdue University and the Glyphosate, Weeds and Crops Group collaborated on an informative brochure focusing on giant ragweed management. 

What has been your experience with giant ragweed? Have you had trouble controlling it? What practices have been successful in your fields? Do you believe you have resistance?