In last week’s Delta Farm Press I wrote about sprangletop — tighthead sprangletop in particular. This week I will discuss controlling the sprangletop species. You go after sprangletop with the herbicides Command, Ricestar HT and Clincher.
Some of the worst sprangletop fields I observed last year were in Clearfield rice where no Command was used. I still have farmers tell me they do not need Command because Newpath and Beyond are effective grass herbicides.
Newpath and Beyond do have good activity some grass species. However, both tend to be weak on both species of sprangletop and especially on tighthead.
Newpath is better on loosehead sprangletop and can be hit or miss on this species if you use it as a soil-applied herbicide. It is almost always a miss on both species if they are emerged.
In addition to sprangletop problems in Clearfield rice last year, I saw a lot more problems with barnyardgrass control with Newpath and Beyond compared to previous years. I hope it was just “the year.”
Therefore, while weed control in Clearfield rice can sometimes be successful without Command, I consider it a necessary component of a Clearfield program. Command was left off most of the Clearfield fields with major grass control issues that I see or get calls about.
Command for sprangletop control is rated the same on loosehead and tighthead in the Arkansas Extension recommendations. However, as I wrote last week, the sprangletop species are saturated soil germinators. While Command may provide good early control, it is possible to get a flush of sprangletop after the Command has degraded below the level of effective control.
In fields that have a history of sprangletop, especially tighthead, I recommend using a two-shot approach with the Command. Apply most of a labeled rate as a pre-emergence treatment and then add Command up to the maximum seasonal use rate to the first postemergence application.
In conventional rice, the first postemergence application may be propanil, Clincher, Ricestar HT, Regiment or even Facet. Adding Command to any of these can make a good postemergence treatment in different situations, and will lengthen the residual grass control period.
If any sprangletop is emerged, however, Ricestar HT or Clincher will be the herbicide of choice in conventional rice to mix with Command. If the situation is Clearfield rice, use a pre-emergence application of Command and then add some to the first Newpath application to extend the residual period.
Once sprangletop has emerged, Ricestar HT and Clincher are the only postemergence herbicides that have good sprangletop activity. Loosehead sprangletop is relatively easy to control in most cases although I saw exceptions to this last year.
In most cases, I do not worry too much about controlling the loosehead species regardless of its size. Tighthead sprangletop is more difficult to control with both herbicides. This species is easier to control when it is small.
In preflood situations I recommend Ricestar HT because it is more consistent over a range of moisture conditions. However, it takes a full 24-ounce rate and I do not recommend that it be tank-mixed with anything other than Command when tighthead sprangletop is present.
Postflood, when tighthead sprangletop is the primary grass species, I have again found 24 ounces of Ricestar HT to be the treatment of choice. However, when the postflood situation includes both sprangletop and barnyardgrass, I usually recommend Clincher.
One of the keys to effective tighthead sprangletop control is proper early identification. At first glance it can resemble barnyardgrass. This can result in a wrong choice of herbicides early and then it is missed until it blows through the top and heads out.