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Diversity in rice weed control

Several people have asked me about the discovery of Command-resistant barnyardgrass in Arkansas. My first thought is the weed population is dynamic or ever-changing. That and the fact there is currently no new technology development for weed control in rice, illustrate the point that if technology isn’t moving forward it is going backward.

There is not much an individual farmer (or weed scientist, for that matter) can do about this but hope technology development will start moving forward again in some fashion.

From a weed management standpoint, I see no reason for panic or radical changes in the conventional rice weed control program. I do see the need for more diversity. The more changes or diversity you throw at any pest, the better your chances of managing resistance.

We are creatures of habit; we find our comfort zones. Once we find a comfort zone, the tendency is to stay in it until something moves us out of it.

Early in my career, I often used the saying, “If it isn’t broke, don’t fix it.” That doesn’t suggest much diversity. We now know that doing the exact same thing we did last year for weed control — because it worked so well — can be the wrong thing to do.

Most weed management programs, especially in conventional rice, are going to begin with Command. I still believe that Command offers the most bang for the buck in a rice weed control program. One only has to look at the overall level of weed control in the rice crop each year to see “that as the Command activity goes, so goes the weed control program.”

In years like last year, when much of the Command is properly activated, we have excellent overall weed control. In dry years when much of the Command is not activated, a lot of farmers struggle to control grass.

There are ways to bring diversity into the weed control program where Command is used.

Since its introduction, Prowl plus quinclorac (Facet or Quinstar) has been an outstanding delayed pre-emergence treatment. Quinclorac prices have come down some, making the treatment more attractive.

Water management issues with the delayed pre-emergence programs make them more difficult to use than Command. Some farmers ask about substituting Prowl for Command. It also is a delayed pre-emergence treatment, meaning rice seeds need to have imbibed germination water before the treatment is applied.

Seed planted in a moist, firm seedbed may imbibe water without a rain or flush. In many situations, however, a rain or flush is needed before application.

Even when properly activated, Prowl alone is much more inconsistent than Command.

Some farmers ask about mixing Prowl with the Command. This can introduce some diversity, but it makes for a delayed pre-emergence treatment instead of one you can spray anytime after planting that you wish.

What about mixing Command and quinclorac as a pre-emergence treatment? In situations where it may be difficult to apply quinclorac postemergence, this makes a nice treatment. However, there are a lot more situations where I prefer to split things up and use the Command pre-emergence and the quinclorac postemergence.

There are more opportunities to introduce diversity into a program following a Command pre-emergence treatment than perhaps there are substitutes for the Command treatment. I will go there next.


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