Fields should be watched closely and the earlier the grass is dealt with when it emerges out of the flood, the better it can be controlled.
Most of the Arkansas rice is flooded by now and the remainder will be shortly. The crop always looks great when the water and nitrogen first hit it. It can also look deceptively clean.
A lot of farmers and consultants have struggled with preflood weed control. A lot of residual herbicides did not receive timely activation. In addition, uneven emergence of the rice in a lot of fields combined with drought-stressed weeds and windy days often made postemergence weed control difficult.
Most kept banging away at it and eventually got fields in decent shape. However, I suspect there are a lot of fields that are not as clean as they look after flooding. I will be surprised if we do not have a lot of grass emergence through the flood. As my mentor Bobby Huey used to say, “We will have fields heading in June and we do not have any rice varieties that head that early!”
Fields should be watched closely and the earlier the grass is dealt with when it emerges out of the flood, the better it can be controlled. My first choice herbicide for postflood barnyardgrass control is usually Regiment. However, corn, grain sorghum, soybeans and cotton are all susceptible to Regiment and must be worked around. Be sure to use the proper adjuvant as recommended on the Regiment label.
Where the escaped grass is sprangletop, I usually recommend Ricestar HT. I have found it to be more consistent on the sprangletop species than Clincher.
However, where the escaped grasses are a mixture of barnyardgrass, sprangletop and even broadleaf signalgrass, I usually recommend Clincher. Ricestar HT and Clincher are safe to soybeans and cotton, but you must be careful around corn and grain sorghum. The increase in corn and grain sorghum acreage is making postemergence rice herbicides even more difficult to apply than normal.
I receive a lot of questions about tank mixtures for postflood weed control. More often than not you need all of the help you can get. Ricestar HT plus Regiment is one combination I get asked about a lot. That combination can work well on grass mixtures as long as there is not a lot of tighthead sprangletop in the mix. I have seen it fail on that species due to antagonism.
I have also seen failures on tighthead sprangletop when Ricestar HT is tank-mixed with a quinclorac (Facet) product. Usually when I recommend Clincher, I recommend that it be tank-mixed with a quinclorac product. The exception would be where the predominant grass is tighthead sprangletop. Some are choosing a split application of Clincher instead of a tank mix.
In Clearfield rice for escaped barnyardgrass and sprangletop, the above options are all applicable. A lot of consultants also choose to salvage with Beyond. I usually recommend Beyond in combination with the herbicides listed above. I pick the tank mix partner based upon the predominant grass species present.
About all I know to say about soybean weed control is to spray early and spray often. In Roundup Ready soybeans, one labeled rate of Flexstar is the limit if you are going to rotate to corn, grain sorghum or rice. If Prefex or another fomesafen product was used earlier, then no Flexstar is recommended. However, you can follow with Ultra Blazer or Cobra as they have no residual activity. For any of these herbicides to work, the weeds must be very small. If the first application does not make crispy critters, spray them again in seven to 10 days.
In LibertyLink soybeans you do not have to worry about residual carryover, but the same timing principles occur. Spray the first application as early as you can. If you fail to get complete kill in five or six days, repeat the treatment in seven to 10 days as above. Bob Scott consistently has excellent results on big pigweeds with two applications of Ignite or Liberty seven to 10 days apart. The trick is to not let them recover from the first application.