Success sometimes comes with a price.

Glyphosate has been a very effective herbicide and its use also has environmental benefits, such as simplifying weed control in reduced-tillage farming. It has allowed growers to switch from conventional-tillage practices to no-till systems that reduce labor costs, improve soil quality, and help curb soil erosion.

Glyphosate’s popularity, and the common practice of using it with no other herbicides, has led to the emergence of a dozen glyphosate-resistant weeds. Growers who stop using glyphosate often go back to tilling their soil, reversing the improvements in soil quality seen over the past decade.

“Widespread use of glyphosate, often to the exclusion of other herbicides, ensured that weeds capable of surviving the material would thrive. Now that we’re seeing that happen, we need to address it,” says Dale Shaner, a plant physiologist who recently retired from the Agricultural Research Service Water Management Research Unit, in Fort Collins, Colo.

Shaner is working as a collaborator with Monsanto to develop a kit that growers could use to determine whether weeds in their fields are glyphosate resistant. Thomas Potter, an environmental chemist at the ARS Southeast Watershed Research Laboratory in Tifton, Ga., is evaluating a herbicide that some cotton growers are using as an alternative.

Value of early detection

One key to addressing the threat posed by glyphosate resistance is early detection. 

“If resistant weeds are detected early, you can minimize the problem by either using another herbicide or, in the case of Palmer amaranth, one of the most difficult weeds to control, getting into the field to pull it out.” Shaner says.