2008: ‘sprangletop year’ in many rice fields

This year seems to get tougher as we go. A state-wide rain would sure do wonders. I continue to get late-season calls about grass coming through the canopy of rice.

A lot of folks have said this is a “sprangletop year.” Because sprangletop germinates in saturated soil, the recent wet spring increased the problem.

There are two species of sprangletop that cause problems in rice — tighthead or Amazon sprangletop (commonly called Christmas tree grass) and loosehead sprangletop. Loosehead is easily identified by its long slender pale green leaves that have a distinct white midrib.

Tighthead sprangletop throws more people because it does not look at all like loosehead in the vegetative stage. It is brighter green in color and does not have the distinct midrib. I often describe it as looking like barnyardgrass with a distinct ligule in the leaf collar region.

Both species have very distinct ligules.

Ricestar HT and Clincher are the two herbicides that have activity on the sprangletops and each can work well on big sprangletop in the flood. With both herbicides, however, loosehead sprangletop is easier to kill than tighthead.

The University of Arkansas rates both herbicides a “9” (on a scale where 10 is complete control) on loosehead and an “8” on tighthead.

As I stated in last week’s article, different people prefer one herbicide over the other. I won’t argue the issue either way. Where the problem is strictly sprangletop, I usually recommend Ricestar HT — especially if it is being tank mixed with something else. A lot of Ricestar HT is going out with Beyond or Newpath in Clearfield rice and with Regiment in conventional rice to pick up sprangletop.

My first recommendation is to use the 24-ounce rate in the tank mix. The second recommendation is to use the tank mix if the sprangletop is loosehead but make separate applications if it is tighthead because you often get some tank mix antagonism which has the effect of reducing the Ricestar rate.

With loosehead sprangletop there is usually plenty of activity left to control it. However, with the tighthead species you need all the activity you can get from a 24-ounce rate.

On big barnyardgrass in the flood, I have the most confidence in Regiment with the new surfactant package. It can be applied only up to joint movement and will injure rice if applied later.

A lot of consultants are applying Grasp in big barnyardgrass situations — especially if weeds such as indigo are also present. In addition, Grasp has a 60 day preharvest interval instead of a joint movement cutoff.

A salvage type treatment that is becoming more popular is Regiment at 0.5 ounce and Ricestar HT at 24 ounces per acre with Dynapak or a similar additive.

Other good big grass treatments are Clincher plus Facet or Quinstar and Ricestar HT plus Facet or Quinstar. The preharvest intervals on Clincher and Ricestar HT are 60 and 65 days respectively. Keep in mind though, a good big-grass treatment does not always mean it will provide complete control.

With any of the above treatments, big grass is tougher to kill than small grass.

Midseason broadleaf herbicides are also being applied on the earlier planted rice. Do your best not to slip up. The cut-off on both Grandstand and 2, 4-D is 0.5-inch internode elongation.

This is about the time of year I will begin to get calls along the lines of “the joint is 2 inches and I did not get 2,4-D or Grandstand out… am I going to hurt anything if I apply it now?” Nobody can really assure you that you will not.

You have to consider the average because all plants and tillers will not be at the same stage. In addition, the further the joint has moved, the higher the risk that injury can occur.

The best way to be sure is to apply it before the 0.5-inch cutoff.

As I have said in the past several articles, this is a throw-the-book-out year. Call if I can help.

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