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Herbicide resistant weeds costing farmers millions in lost yield, increased expense


The biggest problem in dealing with the herbicide-resistant weeds that have become the bane of Mid-South farmers isn’t weeds or herbicides, says Larry Steckel.

“Rather, it’s human nature,” he said at the annual conference of the Mississippi Agricultural Consultants Association at Mississippi State University. “It’s denial by the grower — I’ll wait one more year; I’ll get by one more year.

“You just cannot do that. You’ve got to manage the problem from the very first day you see these weeds in your field; otherwise, before you know it you’ll be behind the numbers curve, with resistant weeds everywhere, and you’ll have a battle royal on your hands.”

That can cost money two ways, says Steckel, who is associate professor/row crop weed specialist in the University of Tennessee Department of Plant Sciences at Jackson.

“First, you lose money from the yield you don’t get because of competition from the weeds, and second, from the cost of the herbicides you throw at the weeds that won’t work. Once Palmer pigweed gets above 6 inches tall, there’s no herbicide that will control it.

“We had a grower who spent $75 per acre on herbicide trying to control pigweed that had got away from him in a 220-acre field. The herbicide didn’t faze the weeds. He ended up not even putting a combine in the field.”

The speed with which resistant Palmer pigweed has spread “is amazing,” he says. “It was first identified in Macon County, Ga., in 2005. We found it a year later in three west Tennessee counties. It’s now in over 200 counties across the South. In middle Tennessee, we now estimate 50 percent of the crop acres are infested and in west Tennessee, 90 percent.”

UT specialists have estimated the economic impact of resistant weeds on Tennessee agriculture, Steckel says.

“In soybeans, we estimate it now costs $35 per acre for herbicides above what growers would have spent when they could control weeds with Roundup. That’s $56 million in additional herbicide costs. Increased herbicide application costs add another $8 million. With a 17 percent yield loss for average 35-acre soybeans, that’s another $40 million.

“That’s a loss of $104 million for soybeans alone, and that’s a conservative estimate. Add about that much more for losses in cotton, and you’re talking more than $200 million — an absolutely staggering figure as a result of herbicide-resistant weeds. Those numbers would be even greater in Mississippi, which has a lot more row crop acres than Tennessee.”

The $200 million-plus doesn’t include the $35 to $100 per acre some growers have spent on hand weeding of resistant weeds, Steckel notes.

“That in itself is an ironic commentary, considering all the advances that have been made in agriculture — site specific management, wonderful new genetics in cotton, corn, and soybean varieties, more effective fungicides and insecticides — yet, in a real sense we’ve been set back 25 years in terms of weed control.”

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