Jim Burton of North Carolina State University’s Horticultural Science Department is studying the genome of herbicide-resistant Palmer amaranth in hopes of learning more about the genetic adaptation that has allowed the plant to resist herbicides like glyphosate.

Burton, who specializes in weed science and herbicide behavior in plants, believes that learning more about Palmer’s resistance could lead to the creation of crops that can adapt to other hardships, including drought, and could ultimately help farmers better deal with resistant weeds.

For years, farmers have relied on the convenience of genetically modified crops to easily manage the problem of weeds in their fields. Roundup Ready crops like cotton, soybeans and corn allowed growers to manage weeds by spraying entire fields with the herbicide glyphosate without damaging crops. But heavy reliance on Roundup Ready crops has led to the emergence of weeds that are resistant to Roundup and other herbicides.

“Roundup has proven to be a very effective weed management tool. But if you use only one tool in your toolbox, when it comes to weeds, you’re going to shoot yourself in the foot,” Burton said.

Roundup-resistant weeds, like the voracious Palmer amaranth, have left growers with few tools to keep weeds out of their fields. In some cases, these resistant weeds are so invasive they even cut into crop yields. North Carolina State weed scientist Alan York estimates that about half of all Palmer amaranth populations in eastern North Carolina are resistant to glysophate, and about half show resistance to another class of herbicides, ALS (acetolactate sythase) inhibitors. A quarter of all Palmer is believed to be resistant to both types of herbicides.

Currently, better management strategies show the most promise for controlling this resistant weed, and North Carolina State weed scientists are working to educate growers. “In my opinion, the overall level of control growers are achieving is better now than it was three or four years ago,” York said. “The problem is not going away; it is just something growers will have to deal with from now on.”

When Roundup Ready crops first became available, scientists believed it would be difficult for weeds to develop resistance to glyphosate, so they were surprised when resistant strains of Palmer began showing up in fields of the Southeast.

“In 1980, people said, ‘Herbicide resistance is never going to be a problem.’ But with resistance, if you don’t manage for it, you’re lost.”