Johnsongrass becomes the 9th glyphosate-resistant species in the U.S.

Two areas in the southeast United States have confirmed Johnsongrass to be resistant to glyphosate herbicides. A recent article in Wallace’s Farmer said populations were confirmed in southeast Arkansas and near Clarksdale, Miss.

In both cases resistant weeds were in fields with a history of continuous Roundup Ready^® soybeans. A recent panelist for a Syngenta Webinar on glyphosate resistance for Southern retailers, Dr. Trey Koger, Mississippi State University, is actively working with the Clarksdale grower to control the population from spreading. Koger mentions in the article that they are managing the situation with other chemistries and equipment inspections. He notes that the field has responded well to graminicides.

Johnsongrass is the third weed, after Italian ryegrass and horseweed (marestail) to become resistant in Mississippi. In Arkansas, it is the fourth glyphosate-resistant weed, behind horseweed, common ragweed and Palmer pigweed.

How worried are you about Johnsgrass developing resistance in your area? What about other grass species, such as foxtail? Are there other weeds exhibiting symptoms of glyphosate resistance?

For more information about other weeds to watch click here.

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