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Washington State University Adams County Extension director Aaron Esser calls BASF’s new product a “game-changer” for fighting wireworms.

A new seed treatment that helps wheat growers kill wireworms was recently approved by the Environmental Protection Agency, and a Washington expert calls it a “game-changer.”

Teraxxa, from BASF, uses the active ingredient Broflanilide, in a new class of chemistry, Insecticide Resistance Action Committee Mode of Action Group 30, according to a company press release.

The ingredient binds to the wireworm’s central nervous system, causing hyperactivity of nerves and muscles, ultimately killing the wireworm. Field trials showed 80-90% reduction in wireworms.

Aaron Esser, Washington State University Extension agronomist, has been studying wireworms since 2008. He’s tested many ways to reduce wireworm populations in the soil. He ran a five-year study with the new chemistry in Lincoln County, primarily on spring wheat.

A heavy infestation of wireworms can lead to a yield of zero, Esser said. He has seen areas that typically yield 70 bushels per acre drop to 7 to 11 bushels per acre.

Lack of a wheat crop can further lead to a severe weed population, he noted.

“It historically happens on your best ground,” he said. “When you start losing your best acreage and you end up with a weed infestation instead of a wheat, that’s a double-edged sword, that can hurt. They kind of sneak up on farmers.”

After using the new chemical, Esser said he found only two immature wireworms in traps the following year.

Other methods averaged 14 wireworms per trap, he said.

He primarily examined the new product’s effect on two species of wireworms, and hopes it will have a similar impact on other species.

“I’ve been doing this too long to say it solves all the problems,” he said. “It may end up creating a different problem. But as far as wireworms, I think it’s as close to a home run as I will see in my career.”

The Washington Grain Commission pushed the state Department of Agriculture for emergency registration for the pesticide on BASF’s behalf, after the process slowed down in the midst of the COVID-19 pandemic.

Any time someone would approach commission vice president Mary Palmer Sullivan with a possible wireworm treatment, she’d ask, “Will it kill them? Because that’s what we need.”

“This has been a long time coming,” Sullivan said.

Farmers haven’t had an effective treatment for wireworm since the chemical Lindane was banned for agricultural use in 2007, she said.

“The wireworm population has been building,” Sullivan said. “In some years, it’s been catastrophic for some growers. This last year was a great example of when conditions are right for growing good wheat, it’s also good conditions for wireworm infestations to become a problem.”

Using a combination of Teraxxa and neonicitinoids will help reduce the risk of wireworms developing resistance to either chemistry, Esser said.

He’d like to study the chemical on winter wheat more closely, and the effect on crop rotations when wireworms are eliminated. He hopes other researchers will examine the effect on wheat grown in irrigated cropping systems.

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