Rice Weed Control 101

Stam + Residual Herbicides- The Most Popular Way To Go

Andy Kendig, State Extension Weed Specialist

Printed/Posted with permission of Mid America Farmer Grower

In the last article we discussed how two or more applications of the non -residual herbicide Stam used to be the textbook weed control program for rice. Now, the most popular route is to use Stam plus a residual herbicide. It is still critical to make this application when grassy weeds are in the 2- to 3 leaf grass stage. However, with residual herbicides- and if the flood is established on time- you can usually get by with a 1-pass weed control program instead of the old 2-pass approach.

Prowl maybe the most popular herbicide in this scheme because of it's low cost. Prowl provides generally good residual grass weed control. The two possible weaknesses with Prowl are that certain broadleaf weeds can emerge between application and flood up and the other is that under wet conditions or when flushing is required for water stress or when the permanent flood is delayed, Prowl can break and you will need to make additional herbicide applications.

Bolero is another commonly-used tank mix partner for Stam or propanil. Bolero's strong points are that it has a slight amount of postemergence activity, it provides excellent control of sprangletop (a grass that can be hard to control) and it has good residual aquatic and broadleaf activity. Bolero's disadvantage would be that it requires wet soil conditions for optimal activity and few Missouri growers are interested in the routine flushing that is required to maintain this activity.

Facet is the newest tank-mix partner and has also gained a lot of popularity. Facet has fair postemergence activity by itself and is an excellent barnyardgrass herbicide. It's mode of action (different from Stam's) and postemergence activity have made this tank mix the favorite for growers who have the propanil resistant grass. Stam and Facet together seem to have an almost synergistic effect, providing more weed control than would be expected. Facet also has one of the longest residual activity periods if moisture is good. The downsides to Facet are that dry soil limit's its activity (however, it doesn't require as much moisture as does Bolero), Facet provides poor control of sprangletop, nutsedge and smartweed, and Facet is relatively expensive.

Growers have used a variety of propanil-Facet mixtures. As you might expect, Rohm & Hass recommends a lot of Stam and a little Facet while BASF tends to recommend more Facet and less Stam. An expensive, but dependable option is to use a full rate of both. This combination can control grasses that have gotten too big for Stam or propanil alone. The full rate of Facet also provides excellent residual weed control and will take care of most growers until flood up. While this is one of the more expensive weed control programs, growers routinely spend even more money trying to be cheap on the front end and then having to clean up later. Some sprangletop, nutsedge and smartweed might grow, but the Stam usually suppresses them well in a full-rate tank mix. We use this herbicide program on all of the non-weed control research at the Missouri Rice Farm and on our Foundation seed blocks at the Delta Center and it rarely fails us.

Finally the herbicide Arrosolo might be a misconception. Arrosolo contains Ordram which is a residual herbicide. However, much like Treflan, Ordram breaks down rapidly if it's not incorporated. And when Arrosolo is sprayed on rice, there is no way to physically incorporate it. A timely rain might give you a little bit of residual activity, but don't count on it with dry soil. However, Ordram can improve the activity of propanil.. Arrosolo is a good postemergence rice herbicide, but it isn't really that much of a residual herbicide.

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