It is now or never for weed control in rice and soybeans. In rice a lot of folks flooded up on more grass than they would have liked.
I rarely recommend skipping a preflood treatment and flooding on grass. However, it got so dry, I reluctantly did so on numerous occasions.
The key to preflood weed control is to catch the grass as soon as possible when it comes through the water. I usually recommend Regiment where the grass is only barnyardgrass. If corn is a complicating factor, I usually change to Grasp. For the sprangletops, I usually recommend Ricestar HT and for multi-species grass situations I usually recommend Clincher. There can be situations where Rebel EX can have a fit, and I also have recommended quite a bit of Ricestar HT and Beyond mixes in Clearfield rice.
The choice of herbicides is situation-specific and also in a lot of cases based upon personal preference. A lot of consultants have found a treatment that works well for them, and experience (both good and bad) is a good teacher.
The longer you wait on grass after it clears the water, it becomes increasingly difficult to kill or even suppress. In addition the different treatments have different cutoff stages or days, so do not get slipped up on.
It is also time for broadleaf herbicide treatments. With Grandstand post flood, make sure the roots are covered with water at application and adhere to the cutoff at 0.5-inch internode elongation. With 2,4-D, also adhere to the half-inch internode cutoff. I hate the calls where the joint movement is on out there an inch or more and the caller wants to know, “How bad will it hurt it?” The injury and yield reduction curve begins to increase at 0.5-inch internode and peaks at about the boot stage. My philosophy of 2,4-D timing is start trying to get it out a little early. Rice is tolerant once it is well-tillered.
I think the 2,4-D recommendation is a carryover from the days we used to fertilize rice differently. Back then we did not apply nearly as much preflood fertilizer and applied a lot more midseason fertilizer. The rice would go into a definite lag period around panicle initiation and really turn yellow. We liked to get the 2,4-D out right then and then fertilize behind it.
Putting most of the nitrogen out preflood now, the rice never lags or turns yellow like that. Therefore, I believe we have more leeway on the front end than waiting until panicle initiation. Therefore, if it means getting it out a little before panicle initiation to make sure you don’t miss the cutoff, my recommendation is to do it.
In soybeans the recommendation is timing, timing and timing! In a conventional or Roundup Ready system the timing goal on pigweeds should be 2 inches in height. You might kill them up to 4 inches but not consistently. Besides they will grow 2 inches a day.
I stopped recommending a fomesafen (Prefix, Flexstar, etc.) product of any type several weeks ago due to the 10-month plant-back interval on corn, milo or rice — even with a single application. Some folks are saying, “I have to use it so I will just wait the 10 months.” Then if we have an early spring and everyone wants to plant in March, the call of the day will be, “What is going to happen if it has only been eight or nine or whatever on my fomesafen?” I will not go there, because I cannot tell you. I have been recommending Ultra Blazer with a repeat treatment a week later.
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In LibertyLink soybeans, shoot for the same 2-inch timing. Liberty is somewhat more forgiving on timing to a point. However, when they are growing 2 to 3 inches a day, that forgiveness disappears in a day or so. Also with Liberty, come right back with a second application a week later if there is any re-infestation or any pigweeds with any green in them whatsoever.
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