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Rate adjustments may be possible with new Provisia rice technology

Provisia herbicide may offer some flexibility in the rates that can be applied, LSU AgCenter weed scientist says

Rice can behave quite a bit differently in a field setting than it does in small plots that are three rows wide and two feet long.

That’s how Eric Webster, weed scientist with the LSU AgCenter, began his discussion of reports of crop injury in some of the seed increase and demonstration plots of the new Provisia rice system in Louisiana and Arkansas this season.

“Sometimes if you get a little bit of wind burn in a plot or you get insect movement into it, it can be difficult to tell what’s going on,” Dr. Webster told rice growers and industry representatives attending the LSU Rice Research Station Field Day in Crowley, La.

“A lot of times you don’t really know what a new product or a new herbicide is going to do until it gets in the hands of the growers, and you start seeing what’s happening in the field,” noted Dr. Webster, who has been working with the new Provisia rice almost since the day Steve Linscombe, the rice breeder at the LSU AgCenter, began placing it in those small plots.”

Dr. Webster has applied 15.5 ounces of Provisia, formerly known as quizalofop or Assure, in test plots at the Rice Research Station in Crowley and at its South Farm south of Crowley. He has also applied 31 ounces per acre, which is, in effect, a 2X rate of the grass herbicide, which he used for a number of years to control red rice in soybeans.

Applying a 2X rate

“What we did on the South Farm on a large area – two 15-acre blocks plus another 15-acre block in the crawfish area – was actually put 31 ounces out in one application,” he said. “And where we saw the main issues was where we were overlapping. So we went from a 31-ounce rate to a 62-ounce rate, and we were putting out quite a bit of Provisia on that rice.”

Dr. Webster said he also believes the rice has been stressed due to weather conditions this year. “We’ve had a lot of days just like this,” referring to the cloudy, overcast skies that dominated during the field day on June 28.

“If you think back to the days when we first got Whip herbicide, we always had trouble with injury when we got three or four days of cloudy weather, and even more so if that was coupled with a fertilizer application,” he said. “So a lot of times with Whip we would back off the rates a little bit.”

He reminded growers that when they were applying Assure to control Johnsongrass and red rice in soybeans, they frequently were applying lower rates of the herbicide – between eight and 12 ounces per acre – rather than the 15.5-ounce recommended rate for Provisia.

“What I like about this 10-ounce rate,” he said pointing to a plot that had received two 10-ounce applications of Provisia. “If you look across this plot you can see a height difference between the applications.

Third application if needed

“Provisia is extremely active on most grasses, especially the weedy rice. I like it because it gives us a third application. If you think back to the Newpath days when we first got Clearfield rice we had two applications of Newpath and that was it. So the first year we started seeing airplane skips, or place under power lines or in the corners where the sprayer couldn’t get. We needed that third application.”

Two years later in 2004, he said, “we got Beyond, which was sort of a cleanup application. The way I look at these three 10-ounce shots is, if you need it, you have that third application. Or you may be in a situation, and I think the label will say this, you can use that third application in your ratoon crop.

“If we had it, we could spread that out and, basically, buy ourselves an insurance policy for later in the season.”

For more information on Provisia rice, visit

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