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Good start to rice weed control

Most rice weed control programs should begin with Command. I make this comment a lot, but as the Command goes — so goes our overall weed control program.

Some still ask: Why use Command in a Clearfield program since Newpath and Clearpath are good on grasses?

There are several reasons why I recommend it. First, the Command will simply reduce the grass pressure to let you focus the Newpath and Beyond herbicides primarily on red rice. If you have a big flush of grass emerge with the rice and red rice, it will often just overpower the first Newpath application and then the fight is on.

Another reason is the increase that is occurring in tighthead sprangletop, especially in Clearfield rice. Beyond is better on sprangletop than Newpath, but both can be very inconsistent. Command simply provides a first line of defense for this weed.

Perhaps the biggest reason to begin the Clearfield program with Command is for resistance management. If we allow barnyardgrass resistance to the ALS-inhibiting herbicides (Newpath, Beyond, Regiment and Grasp) to blow up, the value of the Clearfield system will become greatly diminished.

I would not have said this three years ago, but I now consider barnyardgrass resistance a bigger threat to the Clearfield technology than red rice resistance. This does not mean that stewardship efforts on red rice resistance management should be relaxed. They need to be stepped up.

The only way to really steward the technology for red rice resistance is to rotate with alternate crops. However, for barnyardgrass resistance management, at least you can use other modes of action within the system. You may be thinking, “I am using Clearpath, which gives me a second mode of action with the Facet component.” That is true, but there is enough quinclorac (Facet and others) resistance across Arkansas that I do not believe this treatment alone is a sound resistance management alternative.

My recommendation is to begin both a conventional and Clearfield program with Command, or in some cases where you could make it fit, an alternative like Prowl plus quinclorac delayed pre-emergence. Hopefully you will get this first treatment activated. Then look for ways to get a second residual treatment out and activated before any grass emerges.

There is an increased interest in the split applications of Command. This is a good approach to extend the residual period on barnyardgrass, and I particularly like it on tighthead sprangletop. It will need to be mixed with something. It will often be mixed with a quinclorac product.

Keep in mind, both in Clearfield and conventional rice, most of the quinclorac-resistant barnyardgrass populations the University of Arkansas has tested have been much more susceptible to soil residual treatments of quinclorac than to postemergence treatments. Therefore getting a mixture containing quinclorac in conventional rice or a Clearpath treatment in Clearfield rice out before grass emergence is often the best use of the product.

There are alternatives to quinclorac for a second residual treatment, either mixed with a second application of Command or alone. There is more Prowl going out in second residual applications.

There is an increased interest in thiobencarb as Bolero alone or in Ricebeaux. Different combinations with Prowl or thiobencarb can make nice second residual applications and mix up the resistance management programs in conventional and Clearfield rice.

To date we have no confirmed resistance in Arkansas to Prowl and thiobencarb. I like Bob Scott’s statement in a grower meeting: “I have a hard time building a program strictly around Prowl or thiobencarb but they have a good fit in other proven programs for resistance management.”


TAGS: Rice
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