Managing Resistance with Residual Weed Control in Your Rice Crop

Weed pressure isn’t news to rice growers. Barnyardgrass, specifically, is one perennially troublesome weed that remains an issue across rice production systems. Herbicide resistance adds to the challenge.

“We're running out of postemergence options for barnyardgrass,” says Mallory Scott, field market development specialist for Valent U.S.A. “But we have trusted Bolero.”

Bolero® Herbicide fits conventional drill-seeded, water-seeded and Clearfield® rice applications and provides residual control – key for managing yield-impacting weeds.

Frank Carey, senior manager of field research and development for Valent U.S.A., calls barnyardgrass the Palmer amaranth of rice production. He notes that the crop-competitive barnyardgrass has developed resistance to several modes of action. For most soil-applied herbicides, he says there is a barnyardgrass population somewhere in the Mid-South that has likely developed resistance to that mode of action.

While it may require a change in mindset for some growers, applying Bolero as a delayed preemergence herbicide three to five days after planting may help boost barnyardgrass control.

“Delayed preemergence applications are made between preemergence and early postemergence, after your seed has been planted and your rice seed has imbibed moisture and germinated,” Scott explains. “You let your rice seed get started, and it may not have really taken off above ground yet but go ahead and apply that Bolero. It’s a little different scenario than what people may be used to, but it sure is worth it.”

Whether a herbicide application is made preemergence, delayed preemergence or postemergence, having available moisture in the soil is key to achieving optimum performance. “It doesn't have to be soppy, doesn't have to be super muddy, but it needs to maintain moisture throughout,” Scott advises.

Compared to some competing herbicides, a differentiator for Bolero is its ability to control more than grasses. The broad-spectrum activity of Bolero helps control annual sedges, such as rice flatsedge, as well as some small-seeded broadleaf weeds and aquatics.

For postemergence control, Regiment® Herbicide also offers control of barnyardgrass, rice flatsedge.

“When barnyardgrass is small, you can kill it with a lot of options, but when it reaches the fourth leaf stage, options get limited. And by tiller stage, you’ve really only got one option and that's Regiment,” Carey says.

Adds Scott, “It's easy to control when it's small, and it may be small when you put in your order for the plane, but the way things go in the Mid-South, it may be two or three weeks before the plane gets out there and then you’ve gained another leaf or two.”

Scott recommends incorporating herbicides to achieve optimum control of weeds such as barnyardgrass. And for growers seeing problems sedges, League® Herbicide should also be part of the strategy.

Adding League to a preemergence herbicide tank mix helps provide control of early-season weed competition from sedges and small-seeded broadleaves.

“It is an ALS mode of action but when you apply it at preemergence, it sets it apart from the rest. Growers aren't used to being able to control those weeds with an ALS like they can with League,” Scott says.

League also provides control of hemp sesbania – also known as coffeebean or indigo.

“League does a really good job on sedges and broadleaves from a preemergence standpoint and also gets some postemergence activity,” says Carey. “Its strength is its residual control of those weed species.”

For more information about the rice herbicide portfolio from Valent U.S.A., visit Valent.com, or contact your local retailer or Valent U.S.A. representative.