Monsanto's genetically modified crops are no longer the only "Roundup Ready" plants growing in farmers' fields.
A New York Times article reports that at least 10 species of weeds in 22 states have built up resistance to the popular pesticide.
This is a problem because more weeds means either more pesticides or more manual labor to pull the weeds, according to farm experts.
And the super weeds could also lead to lower yields, increased pollution from pesticide runoff and ultimately higher prices at the grocery store.
Experts Not Surprised
Roundup-resistant weeds come as no surprise to some experts, many of whom predicted over a decade ago that the genetic mutations that lead to resistance are common, and could cause problems for genetically modified crops.
Marion Nestle, author of the Food Politics blog, writes that she met with Monsanto executives in the 1990s to discuss the problem of weeds developing resistance. They dismissed the issue as a "hypothetical" situation.
Now that it is a real situation, Nestle and others are once again calling for an increased emphasis on sustainable organic agriculture.