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Controlling grass weeds in rice

In an earlier article I wrote about the use of pre-emergence herbicides in rice and discussed the fact that every grass plant you control before it emerges is one that does not have a chance to escape.

I also discussed tying a pre-emergence herbicide application to a rain or flush to the extent you possibly can. The aerial label for Command has added a lot of flexibility to accomplish this.

There are also similar options with Facet or Quinstar (quinclorac). One of the things that the resistance testing done at the University of Arkansas has shown is the quinclorac-resistant barnyardgrass lines tested to date have been much more resistant to postemergence applications than to pre-emergence applications.

In heavy barnyardgrass infestations, I like programs that utilize split applications of Command, Command pre-emergence followed by quinclorac in front of the next rain or flush, or combinations of the two. The split applications give you the option of getting a “one-two punch” on the barnyardgrass before it ever emerges.

Also, by splitting the treatment you have not put all the eggs (and the money) in one basket, depending on the same rain for activation.

Well, the best laid plans do not always work out they way we are supposed to and we always have plenty of barnyardgrass and other grasses to fight postemergence. In fact, where only Command is used, there will normally be more broadleaf signalgrass escapes than barnyardgrass or sprangletop.

I do not worry about signalgrass as much because it is easier to kill postemergence than barnyardgrass. When you get into situations with emerging barnyardgrass, you have to hit it quick and hit it hard.

In many cases the days of killing three-leaf to four-leaf barnyardgrass with 3 to 4 quarts of propanil are over — even when resistance has not been confirmed. It just seems as if barnyardgrass, once it gets up and going, is more difficult to kill with any of the herbicides. It is often pretty easy to kill 80 percent of it but the other 20 percent will cause headaches, added expenses and monetary losses all year.

When you get escapes there is no such thing as spraying too early, and if you do not get it done by the four-leaf stage, you are getting in the ditch quickly.

I like the postemergence non-residual plus residual combinations best in most situations. First they combine modes of action which help from a resistance standpoint. They are more effective where a mixture of grass species is present. The combination will usually control larger grass and also provide residual control if you get moisture for activation.

In conventional rice the treatments I recommend most are propanil or Ricestar HT plus Command or quinclorac if the grasses are two-leaf to three-leaf or Ricestar HT plus quinclorac if the grasses are larger.

The propanil combination can be good if the grass is primarily broadleaf signalgrass and there are also a lot of broadleaf weeds in the mix. However, because there is so much propanil-resistant barnyardgrass and often sprangletop in the fields, my “go to” recommendation the past couple of years has been Ricestar HT with either Command or quinclorac. We have a lot of propanil and quinclorac resistance around but so far little or no resistance to Ricestar HT.

I am sometimes asked about Clincher in these combinations since it has the same mode of action as Ricestar HT. It can work, but my experience has been Ricestar HT is better preflood herbicide and Clincher a better postflood herbicide.

Where only barnyardgrass is present and especially with broadleaf weeds such as smartweed, Regiment can have a good fit with the recommended adjuvant packages. There are several ways to skin the cat.

The point is to hit barnyardgrass hard and hit it quick. For example, even being the rate cutter that I am I do not hesitate to recommend 22 ounces of Ricestar HT and a half pound of Facet or Quinstar on two-leaf to four-leaf barnyardgrass.

You can mess around some with signalgrass and sprangletop and still clean it up, but barnyardgrass will eat your lunch. I will again quote my mentor, former rice specialist Bobby Huey: “You cannot make a rice crop until you get the barnyardgrass out of it.”

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