January 5, 2010

4 Min Read

When researchers at the LSU AgCenter began working on herbicide-tolerant rice in the late 1980s, they had no guarantee what they were trying to do was even possible.

The researchers, led by LSU AgCenter professor Tim Croughan, screened thousands of rice plants, trying to find just one that showed some signs of tolerance to a specific herbicide; i.e., the plant didn’t keel over dead when sprayed with the standard rate of the compound.

At some point, Croughan, who is now retired, and Steve Linscombe, now the director of the AgCenter’s Southwest Region, selected a rice line that exhibited enough resistance to a herbicide to warrant further study.

They and other AgCenter personnel spent several more years putting the resistant rice into a commercially adapted variety. The AgCenter eventually signed a licensing agreement with American Cyanamid and its successor, BASF Corp., to develop what became known as Clearfield Rice.

That’s one of the reasons why it would be a shame, weed scientists say, if a grower erased all those years of painstaking research by failing to follow the new Clearfield Rice Stewardship Recommendations developed by BASF.

“Stewardship has to be the goal of the entire rice industry,” said Michael Fruge, a representative of Horizon Ag LLC and a speaker at the New Products and Technology Session at the USA Rice Outlook Conference in New Orleans in December. “This technology is too valuable to lose.”

The recommendations, which can be found at www.agproducts.basf.us/edu/clearfield, are carefully designed to prevent out-crossing of pollen from Clearfield varieties to red rice. “We’ve been telling growers ‘you have the power to stop out-crossing with red rice,” says Alvin Rhodes, technical development representative. “You have to use it wisely.”

Rhodes says that includes planning the 2010 crops to avoid situations that can increase the potential for volunteer Clearfield rice plants to out-cross with red rice and create red rice plants that are resistant to Newpath herbicide.

Take fields of Clearfield rice where shattering was a problem during last fall’s prolonged harvest, for example. “The No. 1 concern is that volunteer plants from those fields will carry the Clearfield trait,” says the University of Arkansas’ Bob Scott. “If you do not rotate those fields to soybeans, you may have volunteers emerging at different times, increasing the window for out-crossing.”

Making full use of the Clearfield technology is another precept growers should follow. “Some farmers plant Clearfield, but don’t treat the edge of the field for various reasons,” says Rhodes. “That can also create out-crossing problems.”

Growers should also position fields to avoid worries with drift. “You have to plan for the best approach,” says Rhodes.

Here are the in-season Clearfield Rice production recommendations:

• Start clean – utilize a burndown herbicide at planting.

• Plant Clearfield rice according to seed company recommendations for best cropping practices.

• Apply a residual herbicide, such as Prowl H20, delayed pre-emergence, to increase grass control.

• Make two applications of Newpath herbicide as labeled or one application of Newpath followed by one application of Clearpath herbicide or vice versa. Clearpath may be substituted for only one of the Newpath applications but not both. The second application provides residual for extended weed control.

• Water management:

1. Flush within two days of first application.

2. Initiate permanent flood within two days of second application or as soon as the growth stage of the rice permits.

3. Maintain good soil moisture until permanent flood.

• Maintain weed-free levees and red-rice-free ditches and turnrows.

• Treat with Beyond herbicide to control escaped red rice at a proper growth stage according to Beyond label.

• Rogue for red rice escapes.

• Do not ratoon crop if red rice is present at harvest, regardless of plans to harvest or utilize as habitat.

• Roll and flush Clearfield rice fields after harvest to promote germination of weeds in the fall.

• After frost in the fall, destroy all remaining rice plants.

The recommendations for crop rotation following planting Clearfield rice:

1. Do not plant Clearfield rice in consecutive years in the same field.

2. Rotate to another crop such as Roundup Ready soybeans or corn and use alternate herbicide mode of action for red rice control.

3. In rotation crop use a residual herbicide for red rice and grass control, such as Outlook or Dual Magnum and Dual II Magnum. Do not use an ALS herbicide as the primary residual herbicide.

4. If late-germinating red rice is present in a Roundup Ready crop prior to canopy closure, an application of Roundup is recommended. A non-ALS herbicide should also be used to control red rice and other grasses in soybeans just prior to canopy closure.

5. Do not grow crawfish following growing Clearfield rice. (Plant non-Clearfield rice for use in crawfish fields.)

6. Do not fallow fields following Clearfield rice without repeated field tillage or glyphosate treatments to control red rice.

7. Do not allow any rice to go to seed in a non-rice year of the rotation.

8. When practical, cultivate all rotational crops regardless of herbicide program.

“Clearfield rice is a novel system; it is not genetically altered rice,” says Rhodes. “It’s the only system we have for red rice. There is nothing on the horizon to replace it.”

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