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Residual activity for barnyardgrass control

Last week I talked about $50-per-acre rice herbicide programs and $100 programs. The difference in the two is usually determined by how well your pre-emergence herbicide program performs.

The herbicides with residual activity are Command, Facet, Quinstar, and Prowl. In Clearfield rice you can add Newpath to the list. There are a lot of different combinations you can put together with these herbicides that can work.

First you have to use them and even the Facet, Quinstar and Newpath that have some postemergence activity perform better pre-emergence on barnyardgrass than they do postemergence. Therefore, one key is getting them applied before any grass emerges if possible. If any grass has emerged, add a postemergence herbicide.

The most important factor in making the residual herbicides work is moisture. I am sure you are thinking, “Oh no. He is about to start talking about flushing!” You are right. I am, but before I do I will say I hope all of the rainfall this spring comes just like you want it. If that is the case then flushing never enters the picture.

I recommend starting the weed control program in every field with a pre-emergence application of Command or as an alternative in conventional rice, Prowl plus Facet or Quinstar delayed pre-emergence. In Clearfield rice I also recommend starting the program with Command.

I am not a fan of Newpath pre-emergence because I believe you get much more consistent results on red rice with an early postemergence application. However, with Beyond as a backup, I am easier to talk into it than I used to be — especially where postemergence drift issues come into play. Even if you use Newpath pre-emergence, I recommend adding Command to it.

I started out with the Clearfield technology thinking that outcrossing to red rice was the greatest threat to the technology. Most of the stewardship information I see still has red rice as the main focus. I and other weed scientists I talk to now believe resistant barnyardgrass is a much bigger threat to the Clearfield technology. That is one reason I recommend Command in the Clearfield program.

The other reason is a lot of folks simply could not control barnyardgrass in their Clearfield rice last year using only Newpath and Beyond.

Whatever course you choose with residual herbicides in both conventional and Clearfield rice, moisture is the key to making them work. This means if you do not get a timely rain, flushing is the only thing that will activate them.

Some tell me, “I am not flushing just to activate a herbicide. I would rather just come back with a postemergence herbicide.” This is certainly an option, but we increasingly are seeing failures with postemergence treatments. A failure or even partial failure with the first postemergence program often means the difference between the $50-per-acre and $100-per-acre herbicide programs.

Others tell me, “Doc, have you ever flushed rice on a silt loam soil and packed it in, requiring two more flushes to get a stand?” Yes, but I am sure on a much smaller scale than some of you. You can often compromise by waiting until the rice is spiking and still beat the grass. If you do have some emerged grass and wish to flush the Command, put some Facet in front of the flush.

I am not going to pound on you or attempt to tell you how to farm. I will say, however, that the key to barnyardgrass control is residual herbicide activity. If you have rain coming, or must flush anyway, take every opportunity to get some residual herbicide in front of it — like more than one residual application.

On the flip side, if you have the herbicide out there, moisture is the only thing that will make it work. I know a few farmers who do not mind flushing, but most would rather step on a cottonmouth. A flush in the absence of rainfall can mean $50 per acre off your herbicide bill and be the difference between a clean field and a grassy one.


TAGS: Management
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