Why Isn't Weed Killer Working Anymore?

Weeds started fighting back.

Low Res Glyphosate Reactions Hr jpg
American Chemical Society

WASHINGTON — Farmers used to worry about weeds. Then, herbicides solved that problem.

At least for a while.

In 1997, there were 432 new patents for herbicides; by 2009, there were only 65. Developing broad-spectrum glyphosate and “Roundup Ready” crops worked so well that people basically stopped looking for new herbicides.

But then the weeds started fighting back.

Reactions is a video series produced by the American Chemical Society and PBS Digital Studios.

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