Mid-South Monster Feared By Midwest Farmers

 

 

The news of herbicide-resistant weeds is nothing new to farmers across the country. With the declining effectiveness of glyphosate on certain weeds beginning about seven years ago in the Mid-South region, farmers began relying more on PPO inhibitors like Flexstar ®, Blazer® and Cobra®. But now, University of Tennessee weed scientist Larry Steckel, Ph.D., says a once-major fear, PPO resistance, is now reality for farmers. And it’s even more widespread than first realized.

 

“We are already seeing two-gene PPO resistance compared to the one-gene resistance we saw last year,” says Steckel. “Of all of the fields that we tested this season, weeds in 20 percent of them were found resistant.”

 

 

Now that weeds are showing resistance to both glyphosate and PPO herbicides, farmers in the Mid-South have very few remaining herbicide options left to control the tenacious weeds they face.

 

At the top of the list is Palmer amaranth, the devastating weed that can grow three inches in one day and produce up to one million seeds per plant.

 

“PPO-resistant Palmer amaranth can still be controlled,” says Steckel. “But we must apply herbicides responsibly, in combination with cultural practices, to slow resistance and control this weed moving forward.”

 

Responsible herbicide use includes using a pre-emergence herbicide and tank mixing multiple modes of action, such as metribuzin (group 5) or group 15 (the chloroacetamides like alacholor or metalochlor) herbicides. Incorporating these must-have herbicide procedures with cultural practices, like narrow-row planting or use of a cover crop, will diversify weed-management plans and potentially help slow the spread of PPO resistance.

 

 

It’s not only farmers in the Mid-South experiencing resistance to this class of herbicides. PPO-resistant waterhemp is already widespread in several soybean-producing states. University of Illinois Professor of Weed Science Aaron Hager, Ph.D., says farmers in his state are seeing more cases of PPO-resistant weeds each year.

 

Hager and other experts in the Midwest are encouraging farmers to use many of the same practices for PPO-resistant weed control in waterhemp as Steckel is in the Mid-South. Mixing multiple herbicide modes of action with a residual or pre-emergence herbicide application has proven effective on Illinois fields as well.

 

But as for Palmer amaranth, Hager says the main focus now is the early identification of the weed. If you’re unaware of what you have, Palmer could take over an entire area in just three short years he says.

 

“We know Palmer is already present in some areas of Illinois, and as more populations are showing up each year, resistance is only a matter of time,” says Hager.