Resistance Has Crossed The River
March 2, 2009 When did glyphosate resistance become noticeable? Three years ago?
When did it become a problem? Two years ago?
In west Tennessee, it’s five years ago to both “when” questions.
“It’s been at least five years in Tennessee and I knew it was just a matter of time before it crossed the river,” said Dyersberg, TN, consultant Billy Beegle, as he stood in a Missouri Delta Research Center cotton plot near Portageville, during a Syngenta-sponsored field day in March. And “it crossed the river” means resistance has spread to the Missouri Bootheel and the adjacent north Arkansas Delta. Beegle consults on both sides of the Mississippi River.
So what tipped Beegle off five years ago? “When you spray Roundup and everything out there is dead but one particular weed, you have to say, ‘uh, oh. I have a problem,’” he said.
Beegle added, so far at least, glyphosate resistance in his area has been limited to mostly marestail and not Palmer amaranth (pigweed), which has become a significant problem in the Southeast, particularly in Georgia. “I haven’t seen any that are resistant, but I have had some that took two applications of glyphosate to control,” he said.
Dr. Andy Kending of the Research Center has been taking a hard look at fall-applied herbicides to fight resistance. “We are looking at both Envoke and Valor,” he said. “The treatments were applied in December, but we got a 12-inch rain (before application). Our normal target would be November ideally.”
“We are treating these plots as pure no-till; there was no fall tillage,” Kending said. “What you are seeing in the checks is marestail. We have been working with fall applications of Envoke for two years and so far it has done a very good job in providing residual marestail control.”
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