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Challenges with Clearfield’s dominance

Collectively, Clearfield rice varieties now occupy the top spot in terms of rice acres in Arkansas.

Some sources estimate that as much as 60 percent of the rice in Arkansas is either a Clearfield variety or Clearfield Hybrid. Most consultants I talk to are saying as much as 75 percent of their acres are Clearfield.

Judging from the amount of Newpath drift complaints I am getting, it feels like at least every other field is Clearfield. Whatever the number, it’s a lot, more than ever before. Much like what happened with Roundup Ready corn, many growers I have spoken with are indicating that all their rice will be Clearfield in 2011. If for no other reason than to avoid drift.

Of course, this increase in acres is of great concern in terms of the development of resistant red rice and the further spread of resistant barnyardgrass. In the case of barnyardgrass, I believe we can manage some resistance by simply not relying solely on Newpath and Beyond for grass control.

For example, including Prowl, Facet, Command, Bolero, or a combination of these products applied pre-emerge or delayed pre can significantly reduce the development or chance of developing Newpath- or ALS-resistant barnyardgrass.

Rotation with soybeans is the best opportunity to prevent the development and spread of Newpath-resistant red rice. The worst thing you can do is grow continuous Clearfield rice and use only Newpath. This scenario has been where most resistant weeds have turned up so far.

Another concern that I have is what to do about shattered Clearfield hybrid rice. I have seen or heard about a number of fields where shattered rice from previous years is growing in this year’s crop. In the case of volunteer hybrid, this generation will not be true to its parent type; this volunteer generation can result in numerous biotypes of rice.

My concern is that some may be weedy. If the parent was hybrid Clearfield, only 25 percent will be controlled by Newpath. If the parent was a conventional Clearfield variety, then it will be 100 percent Clearfield and be true to the parent type.

BASF and Horizon Ag have partnered with the University of Arkansas weed science program to evaluate management options for controlling Clearfield-resistant red rice, volunteer or out-crossed hybrid rice, and volunteer Clearfield rice. My location for this trial is at the Stuttgart Research Station and it is a three-year rotational study.

I encourage you to come to our field day at the Stuttgart Station and see this and all the other work going on. The field day is Aug. 11. For more information go to

TAGS: Rice
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