The barn door is open, the toothpaste is out of the tube, Pandora has left the building. Glyphosate resistance is now a fact of life.

Herbicide-resistant weeds will continue to challenge producers of cotton and other row crops to manage tools effectively to control resistant weeds and to prevent losing other weed control chemistries.

It will take a multi-pronged approach to bring agriculture back from the precipice of herbicide resistance, says David Shaw, Mississippi State University professor of weed science and past president of the Weed Science Society of America.

Shaw, addressing the opening session of the Beltwide Cotton Conferences in Atlanta, said growers do have options and that many agencies, organizations and individuals are working to find better weed control strategies to deal with resistant weed species.

It’s a problem many never anticipated. “Early predictions were that glyphosate resistance would not occur,” he said, “because of the material’s unique mode of action, the minimal occurrence of resistance in plants, the difficulty in selecting resistance for glyphosate-resistant crops and target site alterations lead to less fit plants.”

Oops. That assumption “ignored or could not foresee the intense selection pressure placed on agronomic systems,” Shaw said. “More than 90 percent of cotton and soybean acreage shifted to glyphosate-resistant crops. Price reductions made glyphosate the herbicide of choice in no-till systems and reduced rates of glyphosate became common.”

Which led to trouble.

Now, Shaw said, nine weed species in the United States have been confirmed as glyphosate resistant. These include: Palmer amaranth, common waterhemp, common ragweed, giant ragweed, hairy fleabane, horseweed, Italian ryegrass, rigid ryegrass and Johnsongrass.

A concerted effort is underway to identify how widespread the problem has become and what changes weed resistance is forcing farmers to make. “We are concerned that many farmers are going back to more tillage and away from conservation tillage systems,” Shaw said.

Consequently, the Weed Science Society of America, along with other partners, is developing education initiatives to help growers learn how to manage resistant weed species. They have developed a list of best management practices.

Crop rotation includes rotating to other chemistries and selecting crops with different growing seasons—wheat or canola instead of cotton, for instance.

Cultural practices such as changing planting dates or converting acreage to haying, grazing or burning may break the weed cycle.

“Start clean and stay clean,” Shaw said.