Although glyphosate provided superior weed control in the early years, most of the weeds in the dataset showed signs of adaptation to the chemical in just two to three years.

The study says the data show a rapid falling-off of glyphosate effectiveness against seven major weeds after the first couple of years. The authors conclude that intensive use of any one weedkiller like glyphosate year-after-year serves to speed up evolution in weeds to resist it.

Glyphosate-resistant horseweed, or marestail, remains one of the primary weed management challenges in no-till soybean production. Designing effective herbicide control strategies for horseweed is challenging because of its emergence patterns. Read more in this article from Penn State University Extension.