Insecticide Use Up in Rootworm Fight

LAWRENCE, Kan. (DTN) -- Many farmers are returning to the use of soil insecticides as rootworm resistance to Bt-corn hybrids surfaces more frequently across the Cornbelt.

Sales of insecticide and the planter boxes that distribute them have been on the rise for several years with no signs of slowing, chemical and equipment dealers told DTN.

"Ten years ago we were starting to sell more and more planters without insecticide (boxes), but in the last two to three years, it has reversed and most guys want insecticides so they are adding them or trading for a planter that does have insecticide (boxes)," said Tim Burgess, a salesman with Sloan Implement Company in Cuba City, Wis. "It has been a steady rise for the last two to three years."

At issue is the erosion of Bt-corn traits' ability to protect against the western corn rootworm. Since 2009, western corn rootworms have evolved resistance to two single Bt-traits, Cry3Bb1 and mCry3A. Much of the documented resistance has been concentrated in parts of Iowa and Illinois, where corn-on-corn planting placed a great deal of pressure on Bt-traited corn hybrids.

In a DTN 360 poll on insecticide use, the geographic range of rootworm problems was clearly illustrated. Twenty-nine percent of the 404 farmers who participated in the online poll indicated that they had plans to use soil insecticides in addition to corn hybrids with either single or stacked Bt corn rootworm-traits. In states where farmers are most struggling with rootworm resistance, that percentage grew: Around 40% of Iowa and Minnesota farmers and 30% of Illinois farmers who participated expected to add insecticides to their Bt-hybrids.

Growers from states with less rootworm pressure showed less interest in insecticides. Only 10% of Ohio farmers and 12% of Nebraska farmers indicated that they planned to use soil insecticides with hybrids containing Bt traits.

"We don't supply much insecticide because no one seems to see the benefit of adding that on, and they even wonder about using the (Bt) traits sometimes," noted Stan Geiser, from Crop Production Services in Upper Sandusky, Ohio. "West of here, yes there's a need for it. And we used it years ago, to put in planters, but I'll bet in the last 10 or 12 years, since (Bt) traits came out, we've hardly used any at all."

But in parts of Iowa, Illinois, southern Minnesota and western Wisconsin, rootworms are forcing growers back to older management tactics.

Ten years ago, you were crazy to order a planter with insecticide boxes, "There was a savings to not having it on there. Now, everybody's been retrofitting (planters), and now this last year, everybody's starting to price planters with it on."

Burgess estimated that three-quarters of farmers in his area in western Wisconsin are now equipped to use planting-time soil insecticides, up from 60% three years ago.

Although John Deere and Case IH declined to give sales figures on planters, equipment companies appear to be adjusting to the demand. Pat Ubben, store manager of Phelps Implement Company in Hubbard, Iowa, told DTN that although last year's supplies for insecticide boxes were tight, he's been able to meet customers' demands this spring. More planters, such as John Deere's Pro Series units, are coming out with granular insecticide boxes already installed, he said.

Like many equipment dealers, chemical companies and ag supply retailers noticed the change in insecticide demand around three years ago.

From 2011 to 2013, insecticide and Smartbox system sales more than doubled for the agricultural chemical corporation Amvac, Joe Short, the company's Midwest marketing manager, told DTN.

Much of that growth has been in top-corn producing regions of the Midwest, such as western Iowa, which Amvac sales manager Doug DeGraff oversees.

"Sales skyrocketed the last three years because (Bt) traits aren't the answer anymore in a lot of situations," DeGraff told DTN. "We're seeing glitches in first-year corn now with resistance to traits in Illinois, so I think the demand is going to continue to go up."

While the company has seen growth in both granular and liquid insecticide sales, Short said granular products such as Amvac's top-seller, Aztec, remain the best options for growers facing high corn rootworm populations.

Bob Rogers, the agronomy manager for Maplehurst Farms, told DTN that many farmers in his northern Illinois region are adding insecticides as a preventative measure, even if resistance isn't a problem for them yet. He said insecticide sales are up 20% this spring over previous years.

"We haven't seen that huge (rootworm) pressure they've seen in central Illinois, but guys are gearing up for it. They don't want it so they're actually starting to buy insecticide just to avoid it."

DeGraff estimates Amvac's insecticide sales will increase 10% to 20% in his region this year, but the final numbers won't be in until farmers finish making some tough decisions. "The biggest issue now is growers are slow making decisions," he explained. "The economics aren't there -- crop inputs don't look quite as attractive as they have in the past."

Emily Unglesbee can be reached emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

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