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Postemergence options for grass in rice

May 15, 2008 10:12 AM, By Ford L. Baldwin
Practical Weed Consultants, LLC.

As I write, the majority of the rice is still to be planted in many areas of Arkansas. However, calls are beginning to come in about weed control in emerged rice.

I have talked to several consultants who treated most of the planted acres with a pre-emergence herbicide in front of a rain. In some cases they got two applications out and activated.

With the moisture we have had, any field with a pre-emergence herbicide should be looking pretty good. In fact I ran into one farmer in a restaurant the other night and he jokingly told me, “If you had told me it was going to rain this much, I would have used a lower rate of Command — my rice sure is white.”

Those are easy to scout — I have never seen one of those white fields grow up in grass.

As you keep planting, try to stay “sprayed up” with a pre-emergence herbicide. If the weekly showers continue, you have activated chemical out there.

However, my concern in this article is postemergence weed control where you have grass emerging with the rice. There are a lot of postemergence options in both conventional and Clearfield rice.

This early in the season I like contact plus residual herbicide combinations. Hit the grass early and hit it hard.

Broadleaf signalgrass and sprangletop, for the most part, are relatively easy to control. However, barnyardgrass that really gets up and growing seems more difficult to control every year.

In conventional rice, for barnyardgrass that is two-leaf or less, I usually recommend postemergence plus residual combinations with either Command or Facet/Quinstar (quinclorac), depending upon personal choice. Examples would be Stam, Super Wham or Ricestar HT plus Command or quinclorac depending on the other weeds emerged and the resistance situation.

If a lot of broadleaf weeds and annual sedges are emerged and the barnyardgrass is not resistant to propanil or quinclorac, I often recommend a propanil product.

If there is a lot of sprangletop or resistant barnyardgrass present, I usually recommend Ricestar HT.

When the grass is two-leaf or less, it is often a matter of “do something now” rather than what you do. However, when you walk in a field and it is covered up in three- to four-leaf barnyardgrass, correct decisions are much more critical. If you miss it there, you are in trouble.

In those situations, I usually recommend either Ricestar HT plus quinclorac or see if there is a fit for Regiment.

If broadleaf signalgrass or sprangletop is in the mix, my standard recommendation last year was 22 ounces of Ricestar HT and a half pound of Facet or Quinstar. I did not have a single failure call on that recommendation.

If the emerged grass is primarily barnyardgrass, the rice is two-leaf or larger and is not Bengal, Regiment is often a nice fit — especially if broadleaf weeds are present. If you want some residual, or if signalgrass is present, you can add some quinclorac or Command.

In most postemergence situations, resist the temptation to lower the quinclorac rate. If it is a pre-emergence situation and you are just looking to get a little more residual out in front of a rain, you can use some lower rates. However, if you have grass up and you are really trying to kill something, keep the rate at a half-pound.

In Clearfield rice, things can be a little easier because Newpath has a lot of grass activity. However, if there is a lot of barnyardgrass present at the time of the first application, consider giving the Newpath some help. Clearpath is often the treatment of choice and I get a lot of questions on whether to use Clearpath for the first or second application.

There is no single best way. If you are in a fight from the start, use it in the first application. If you are relatively clean at the first application and you want a long residual period, use it as the second application. There are also other choices. We will go there next time.

e-mail: ford@weedconsultants.com