HPPD inhibitors have been the hot ticket in controlling tough weeds for the past few years.

Now, Syngenta is making that ticket even hotter with its new Acuron corn herbicide. Acuron combines s-metolachlor, mesotrione and atrazine with a new HPPD inhibitor – bicyclopyrone.

University of Illinois weed scientist Aaron Hager says the four active ingredients give growers three different sites of action in one product. Bicyclopyrone and mesotrione are both group 27 herbicides. Atrazine is group 5. And, s-metolachlor is group 15.

New Acuron herbicide includes three modes of action

The big news, of course, is the addition of bicyclopyrone – a completely new active ingredient. Tom Kelley, a Syngenta agronomic service representative, notes bicyclopyrone significantly boosts control of numerous weeds, including vine species, grasses and small-seeded broadleaves.

"A lot of growers have been using Callisto (mesotrione only) for years," Kelley notes. "Vine species have always been an Achilles heel for Callisto. Acuron fills in that gap nicely."

Acuron's bicyclopyrone has also proven quite effective on giant ragweed. Kelley says in his east central Illinois coverage area, this has been one of the biggest benefits of the new herbicide.

See it in action
Acuron is now registered for use in the U.S. Kelley says suppliers were able to get product in the hands of growers as of May 1.

With limited supply available for 2015, Kelley says Syngenta is encouraging growers to conduct their own comparison testing. Contact a local Syngenta rep for more information as it becomes available during the growing season. In addition, Syngenta will showcase Acuron in their numerous Grow More Experience plots across the U.S.

In Kelley's coverage area, which is composed primarily of flat, black dirt, the recommended application rate is three quarts per acre as a pre-plant herbicide. If used as a foundation product, in combination with another herbicide, the recommended rate is two quarts per acre.

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The application window for Acuron is 28 days pre-plant up to corn that is 12 inches tall. Kelley recommends spraying weeds no taller than four inches – the height at which weeds begin stealing yield.

Know your MOAs
Even though Acuron has three different sites of action working against weed populations, Hager warns it doesn't necessarily mean all three are effective.

It's no longer enough to know if there's a population of herbicide-resistant weeds on the farm. Hager says growers must know exactly which chemistries are ineffective. Without that knowledge, a product with multiple modes of action may be reduced to one effective ingredient.

"Triazine resistance is fairly common in waterhemp in Illinois," Hager notes. "If a population is resistant to both HPPD inhibitors and atrazine, then you're down to one mode of action in some of these products."

Also, Hager warns growers that extremely high doses of product could mask a resistance problem. PPO-inhibitor-resistant weeds can often be controlled by overwhelming the resistance mechanism with the relatively high doses used with soil-applied PPO inhibitor herbicides.

Lastly, Hager says it's critically important for the farmer to know and understand resistance issues on the farm.

"What we're learning about weed resistance continues to evolve," Hager explains. "Everyone involved with weed management should follow these developments as closely as possible."