Control of Herbicide Resistant Common Ragweed

by Adam Cordy, Sustainable Plant Systems major

Herbicide resistance of common ragweed has increased in recent years in Ohio. Typically, it is resistance to the Group 2, 9, or 14 herbicides (groups based primarily on the herbicide mode of action – in essence, how it acts to kill weeds). No cases of resistance to all three herbicides have been reported yet but at times there have been cases of a combination of these three herbicides.

There shouldn’t be much of an issue controlling common ragweed in corn. In soybeans it can be harder because of the herbicides available to use. An effective herbicide burndown of 2,4-D ester can be used in a soybean crop if it is applied 2 weeks before planting. The best thing to do is to have a combination of preemerge and postemerge herbicides with different modes of actions to battle the weed. Follow guidelines for recommended preemergence herbicides that can help control herbicide resistant common ragweed. Postemergence herbicides can also be effective on controlling common ragweed.

When spraying, weeds should be sprayed before they get much over 6 inches in height. Anything past that can be too mature to effectively be controlled with herbicides.

Tillage can also significantly increase control of the weed. One of the most overlooked aspects is crop rotation. A solid crop rotation and integrated pest management program are the best bet to control herbicide resistant common ragweed.


Loux, Mark M., Doug Doohan, Anthony F. Dobbels, William G. Johnson, Bryan G. Young, Travis R. Legleiter, and Aaron Hager. Weed Control Guide for Ohio, Indiana and Illinois. Columbus: Ohio State U Extension, 2015. Print.

This blog post was an assignment for Societal Issues: Pesticides, Alternatives and the Environment (PLNTPTH 4597). The views expressed are those of the author and do not necessarily reflect the views of the class, Department of Plant Pathology or the instructor.

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