Though not new to the ag industry, it’s new to Federated territory: Resistance in waterhemp to Group 14 herbicides.
“Part of managing this problem is understanding it,” said Kevin Carlson, Federated’s agronomy sales manager. “It’s a little technical,” he said, while describing how the mode of action is cell membrane disruptors, which are the ‘burners’ sprayed post-emerge. The site of action is chlorophyll synthesis inhibitors (PPO inhibitors) which work on the plant as a pre- or post-emerge herbicide, or both – such as Flexstar, for example (see representative list in photo).
“We’ve done the testing and found positive results for resistance to the Group 14 herbicide class,” he said. Weeds that survived herbicide applications are going to seed and their “progeny are passing the trait to the next generation,” Carlson added (see photos above of waterhemp gone to seed, discovered in Wright County this summer).
So what’s the bottom line of this finding in central Minnesota and western Wisconsin? “Take this chemistry class and set it on the shelf,” said Carlson, acknowledging that statement as “alarming,” but the reality is that “this class of herbicides will not work [on resistant weeds].”
“We can’t ignore the need to change our management plan in the future,” he said, “because the current [weed] management plan relying on that chemistry is no longer effective.”
Listen to this audio
from Carlson discussing PPO resistance this year, and what to consider for future years.
“If you have waterhemp that you sprayed with a PPO product, pre- or post-emerge, and it didn’t control it, we can test it to see if you have a resistant population in your field,” said Carlson. The cost is $50 for the test, plus postage. “It’s the cost of knowing,” said Carlson. (Photo above shows a sample report for resistance testing.)
