New rice herbicide passes tough test

A wet spring produced some tough challenges for both rice producers and a newly-introduced broad spectrum herbicide for control of annual grasses in rice, according to Ralph Lassiter, senior development scientist with Dow AgroSciences, during a recent field day, in Stuttgart, Ark.

“It was a challenge for rice growers in that it was cool during the early part of the season, and rice was slow to grow. It was a rainy season, and it was difficult maintaining good grass control early.

“By the time growers were ready to put permanent floods on, they had a lot of grass and were battling to salvage their crop.”

A lot of the new herbicide, Clincher SF, from Dow AgroSciences, went out to control the grass, noted Lassiter. And while the intense grass pressure made coverage very difficult for growers, the herbicide “is doing what we expected and maybe a little more.”

In fact, the herbicide performed well enough this year that supplies were completely exhausted. Inventory issues aside, “As of last week, our complaints were only 1 percent of the total acres,” Lassiter said.

Clincher is a new rice herbicide that provides broad spectrum control of many annual grasses — including propanil- and Facet-resistant barnyardgrass and some perennial grasses in rice.

It's application window is from early pre-flood to late post-flood and fits into drill-seeded and water-seeded rice programs.

Lassiter recommends an application of Clincher a week to 10 days after the flood is applied. “We've had very good results that way if you can get the coverage. In cases where there is very high pressure in grasses, which we had this year, when the application can't get the material down into the canopy, sometimes we get some regrowth. We could kill four of the five tillers on a weed or we could have a side shoot that came out.

“If the soils are dry, Clincher doesn't perform as well as if we have good moist soils,” Lassiter said. “That's probably why the post-flood application works more consistently than pre-flood. We can deliver good control if we have good soil moisture.

“One of the major advantages of Clincher is that it is safe on the crop,” Lassiter added. “We have tested at extremely high rates without hurting the rice. Because it only has activity on grasses, you can use it safely around cotton, soybeans and tomatoes without risk of crop injury to adjacent crops.”

Clincher should not be tank-mixed with postemergence herbicides, including Stam, Grandstand, Permit, Londax or 2,4-D herbicides, due to potential for reduced grass control.

Lassiter also discussed a pending herbicide, known as DE-638 SF (penoxsulam) for residual control of barnyardgrass and many broadleaf and annual sedge weeds. “It has residual activity, where some of the other materials like Clincher doesn't. It's on a reduced risk status with EPA, so we're expecting a registration in 2004 for release in 2005.

DE-638 will also control both propanil- and Facet-resistant barnyardgrass biotypes.

“It has the flexibility for tank-mixing with a lot of other herbicides without causing problems,” Lassiter said. “It fits nicely into the Command program.”

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