GLYPHOSATE-BASED compounds are by far the most popular herbicides in use today, and there's good news and bad for Missouri farmers who use them.

On July 17, the University of Missouri Delta Center Weed Tour gives MU scientists the chance to share data from experiments involving herbicide tolerant cotton varieties and options for glyphosate-resistant weeds, said Andy Kendig, Extension weed science specialist with the MU Commercial Agriculture Program.

The free tour runs from 9:30 through noon at the Delta Center Lee farm, 8 miles Southeast of Portageville at the intersection of state routes T and TT. “This is your chance to see all of the latest weed control technology in corn, cotton, rice and soybeans at one time,” Kendig said.

Much of the current MU weed-control research centers on managing Roundup Ready cotton, which isn't as simple as Roundup Ready soybeans because farmers cannot spray over-the-top after the four-leaf stage, he said.

Roundup Ready Flex cotton will be featured. This cotton has the same over-the-top flexibility found in Roundup Ready beans and “should be available in about two years,” Kendig said. Delta researchers are also testing Liberty Link cotton, which offers the same over-the-top flexibility. “There's a very good likelihood that Liberty Link cotton could be available next year.”

The bad news is that another glyphosate-resistant weed might have arrived in Missouri from Tennessee, Kendig said. “We have not formally confirmed it, but there are a lot of indications we have the glyphosate-resistant horseweed.”

He said no-till programs that rely exclusively on glyphosate-based weed control have contributed to the problem. “If you use the same herbicide year after year, no matter what it is, you're eventually going to get a few resistant weeds. We do have some alternatives for the growers, but we're recommending they rotate herbicides when they can.”

Recent research also focuses on “a lot of interesting stuff in rice,” Kendig said. “Five years ago, choices for weed control in rice were very limited — almost cast in stone. Now, growers have got choices.”

For rice growers, “weed control is less expensive and better, but things are also more complicated,” he said. “Growers now have to scout and mix and match to achieve optimum weed control.”

The weed tour has an informal format, and guests are welcome to view the plots at their leisure and take notes, Kendig said. Besides MU scientist, numerous representatives from agricultural chemical companies attend the tour and often provide useful insight.

The tour is free and open to the public, but interested persons should pre-register by calling the Delta Center at 573-379-5431. Continuing education credit for Certified Crop Advisors should be available. For more information, go to http://www.psu.missouri.edu/deltaweeds.