I have had more than the usual number of calls about joint movement that caught folks off guard getting 2,4-D or Grandstand applied at midseason. “How bad am I going to hurt my rice if my joints are an inch or 2 inches or whatever?” is about as tough a question as “Do I flood or flush and spray or spray and then flush or flood?”
The 0.5-inch internode elongation cutoff on the hormone-type herbicides is simply a guideline. Research has shown that the risk of injury and the degree of injury increases from around 0.5-inch internode elongation through the heading stage.
That does not mean that if the internode length is 0.5 inch that you get no injury, but if it is 9/16 inch you will get severe injury.
Also, there is a big difference in internode length depending on whether you are cutting a main stem on an older plant versus a tiller, or the main stem on a plant that may have come up later. I try to use the 0.5-inch cutoff as a representative average across the field and also weigh the risk of injury against the severity of the weed pressure in the field.
It obviously does no good to tell the guy who has let joint movement get away from him, “When in doubt spray early.” However, when you cut into plants and the older tillers are a few days away from green ring, it is time to get the hormone-type herbicides applied.
As the average internode lengths get beyond 0.5 inch, the risk of injury increases. The callers in that predicament want the good weed doctor to tell them to go ahead and spray and no injury will occur. Sometimes that is not possible.
I also get a lot of questions about cutoff dates for Beyond in Clearfield rice. For CL 161 the cutoff is 14 days past panicle initiation or green ring. A lot of us wish it was even later. It is my understanding, however, for the Clearfield hybrids that Rice Tec is recommending a cutoff at panicle initiation.
There were some reports from good farmers last year who felt rice yields had been reduced by late applications of Beyond on the hybrids. In some situations only spot spraying had been done or only a part of the field had been sprayed and the differences were apparent.
If the treatment is going to cause injury past panicle initiation, then it should not be applied past this point. However, a cutoff at panicle initiation severely limits the use of Beyond as a salvage red rice treatment because the red rice has usually not emerged above the rice canopy by this time. This then impacts the resistance management program.
Hopefully both the companies and the university weed scientists will research this issue further in an attempt to document the injury risk.
While a lot of rice in Arkansas is clean, there have also been grassy fields flooded because it was too dry to apply herbicides preflood.
Where the escaped grass is primarily sprangletop, Ricestar HT and Clincher are the herbicides of choice. I have always felt Ricestar HT was more consistent on sprangletop. With both herbicides, loose head sprangletop is easier to kill than the tight head sprangletop (Christmas tree grass).
Where the postflood weed spectrum consists only of barnyardgrass, postflood applications of Regiment with the new surfactant package have been very effective this year. Regiment should not be applied after panicle initiation.
On barnyardgrass and broadleaf signalgrass, postflood applications of Facet or Quinstar plus crop oil can be very effective if there is no quinclorac-resistant grass in the mix. The quinclorac cutoff date is 40 days prior to harvest.
Where any of the above grasses or a broad spectrum of grasses is present, Clincher or a mixture of Clincher plus Facet or Quinstar is a good treatment.
If the weed pressure is severe, Clincher plus Facet has been more consistent than Clincher alone. Where Clincher is used, the flood must be maintained.