Not Your Average Giant
Many species of glyphosate-resistant weeds are causing concern for more and more growers in states throughout the Midwest, but giant ragweed may be the biggest and baddest of all. With the ability to grow up to 15 feet when left untreated, this weed has the potential to wipe out an entire crop with only a small number of plants.
Giant ragweed has been spotted in Indiana, Ohio, Kansas and, most recently, Minnesota and Tennessee. Because of the weed’s unique ability to germinate as early as March and as late as July, it has growers concerned about its resistance to glyphosate and other herbicides.
Even in dry, less fertile soil, giant ragweed can reach up to seven feet tall and escape many soil-applied herbicides because of its coarse, rough stem and shallow, fibrous roots. Its large seeds enable it to retain more energy and nutrients for seedlings, increasing its life span.
Experts at Syngenta and Purdue University recommend combining a rotation of glyphosate with herbicides, using at least two or more pre- and post-emergence herbicide classes, as well as a multiple-year strategy. The Resistance Fighter website offers detailed information about giant ragweed and the Syngenta 2-1-2 system. To learn more about this fierce weed in Indiana, read Purdue’s Pest & Crop article "Lots of Weedy Fields".