Propanil use down, still important

An EPA representative called last summer to learn about propanil (Stam) for the sake of reregistration. He asked if propanil was still needed given that we have new chemistry like Command, Ricestar, Regiment, Clincher and Newpath.

Things have changed, but propanil is just as important as it ever has been. In the past we'd spray Stam twice and might use upwards of 8 quarts when everything was said and done. Now, some growers get by with Command and broadleaf herbicides, and no propanil.

While Command has displaced a lot of propanil, the most popular followup is propanil plus Londax or Permit (including the Duet-propanil + Londax product).

In the Clearfield/Newpath system, legume weeds (coffeebean and Indigo) escape. There are many choices for those weeds; one of the better choices is propanil tank mixed with the postemergence Newpath application.

Dow sells Clincher and Grandstand (and Stam). Clincher is a grass-only compound, but Stam followed by Clincher (or Clincher followed by Stam) has been a good overall program.

Propanil could work exactly the same with Ricestar. Even though Grandstand is a good broadleaf herbicide, its activity is enhanced by adding a quart of propanil.

Valent's Regiment does some neat things like controlling large barnyardgrass and broadleaf weeds. But without any help, sprangletop, broadleaf signalgrass and fall panicum will escape. When a properly-timed propanil application takes them out, Regiment programs work well.

Finally, don't forget how much the older chemistry of Facet, Prowl and Bolero benefited from propanil.

Propanil-resistant barnyardgrass has reduced propanil use some in Missouri (and a lot in Arkansas). With the new chemistry, propanil may now be more of a broadleaf herbicide than a grass herbicide. But regardless of what we think, there is no harm in our broadleaf herbicide killing some grass.

At the recent Rice Industry Outlook conference I was reminded of the tremendous number of herbicide-resistance problems that plague California rice growers. The most likely culprit is that they stopped using Stam in the late 1960s and switched almost exclusively to Ordram + Londax.

Whatever the weed and whatever the program, overuse can lead to resistance, and that's what they got. We did the same thing here with propanil, but were fortunate to have Prowl, Bolero, and Facet to mix things up.

Now, more than ever before, we need to mix up our weed control programs. We have enough rice herbicides that we can do exactly that.

If you were teaching a weed science course and asked the class to name a herbicide that controlled almost all weeds without harming rice, there is only one answer — propanil. While we finally have several choices and use many fewer quarts of propanil, it's importance is as high as ever.

Andy Kendig is an Extension weed specialist at the University of Missouri Delta Center.

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