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Diversify rice weed control

Last week I ended the article with a comment about how important Command is to our weed management systems in rice. Before I get any e-mails from companies with herbicides other than Command (and now Alert — Cheminova’s newly registered clomazone formulation), let me first say that every single rice herbicide is important.

However, one can look at the level of grass control in rice every season and see that “as the Command goes, so goes the weed control program.” If our spring starts off wet and most of the Command gets activated, weed control is relatively easy in most fields. If the spring starts off dry and timely activation does not occur, the result is often an expensive weed control programs and a grassy rice crop.

In my opinion, the key to holding our weed management systems together in both conventional and Clearfield rice is preserving the clomazone technology.

Last week I stated that two barnyardgrass populations in Arkansas have been confirmed to be resistant to clomazone. Let’s hope that is all of them. However, a population can only be confirmed resistant (or not) if someone pulls samples and has them tested. The fact we have two confirmed populations is enough to tell us clomazone resistance can happen and it should be managed for.

Bob Scott announced in a recent meeting that ALS-resistant barnyardgrass has now been confirmed in Arkansas. Again, the weeds are talking, is anybody listening?

I have stated before that I wish we had a good alternative pre-emergence herbicide to clomazone, but we do not. If you leave it out of the program and weeds grow up, then you have not accomplished anything. I believe conventional weed programs still must begin with Command.

Then, however, the proper steps must be taken to insure that you do not have escapes. I still occasionally get the comment that “Command was all I needed for grass last year.” The comment will often be followed with “I had a few escapes but not enough to worry about.”

It has taken a while for all of us to learn this, but if you had any escapes you had enough to worry about. Escapes can occur for a lot of reasons unrelated to resistance, but you can not afford to take the chance by letting them go to seed.

A lot of consultants are splitting the Command application and adding a second herbicide like quinclorac (Facet and several others now) with the split application. Others are using clomazone and following with a quinclorac application in front of the next rain or flush but before grass emergence. After emergence, treatments like Ricestar HT plus quinclorac or clomazone have worked well. There are plenty of examples to get diversity into the program.

There are two older residual herbicides that can get additional modes of action in a program other than the examples listed above. Some growers and consultants are looking at Prowl again. I believe it is too inconsistent to use alone for barnyardgrass. However, when tank-mixed with clomazone or tank-mixed with quinclorac or a postemergence herbicide like Ricestar HT, it can add diversity. As one consultant friend would say, “It isn’t good enough by itself but it is pretty good if you have it riding in the airplane with something else.”

Another older herbicide that can come back and make a contribution is Bolero. It is available alone and also as a premix with propanil sold as RiceBeaux. Those can be used a lot like Prowl in either soil residual or early postemergence tank mixes.

Remember that with both Prowl and the Bolero-containing products the rice seed should have imbibed its germination water before application.

There are a lot of ways to add diversity and mix up modes of action. The examples are intended to provide ideas. With the patent off nearly every rice herbicide, it is impractical to mention every trade name at every spot in an article. The mention of a specific product does not mean it is favored over other identical products.


TAGS: Rice
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