Rice Weed Control 101

Stam 3 + 3- The Textbook Rice Weed Control

Andy Kendig, State Extension Weed Specialist

Printed/Posted with permission of Mid America Farmer Grower

Economical, drill-seeded rice production in the United States has often been credited to the introduction of the herbicide propanil- known often by it's oldest trade name "Stam". For the sake of political correctness- there are a number of other similar products- some even have the trade name of "Propanil". Regardless of the brand name, Stam or propanil is a basic foundation of rice weed control.

Stam, is a lot like the herbicide Gramoxone. It is a fast-acting, contact-type weed killer and has no residual activity. Good coverage is important and occasional problems arise from low-gallonage (3 gpa) aerial applications. Like Gramoxone, weeds must be small and actively growing. Large weeds will only be burned back. Traditionally, Stam was used twice at 3 quarts per acre (thus the nickname Stam 3 + 3.)

While Stam or propanil can be used in many ways, the "Textbook Traditional" Stam program would be as follows:

  1. Rice is planted into a clean seedbed.
  2. After about 10 days there should be weeds and grasses with 2-3 leaves (Make note of the 2-3 leaf grass stage- it is critical for Stam or propanil activity). Spray these weeds with 3 quarts of Stam.
  3. After about 10 more days the rice should have another flush of weeds and grasses with 2-3 leaves) so spray again with Stam.
  4. Flood the field (ideally) within 4 days of the Stam application (there is no residual and the flood and shading control additional weeds if done timely.)

Again, size and timing are critical. Two to 3 leaf grass means EXACTLY that. Letting grass get too big one of the most common weed control failures. In reality- Stam can kill 4 or 5 leaf grass, but when 80% of the grass is in the 2 to 3 leaf stage, 10% of it is in the 4 to 5 leaf stage. And when 80% of it is in the 4 to 5 leaf stage, 10% is in the 6 to 8 leaf stage and won't be controlled! This point cannot be over emphasized- oversized weeds are one of the most common rice weed control failures.

Another important point on rice weed control in general is that while there are cheaper weed control programs, it is VERY easy to spend MORE money cleaning up a failure than you would spend with a good- though-expensive pre planned herbicide program. With Stam, if the weeds are 2-3 leaf stage and it's too wet to use ground equipment, by all means call the airplane. The extra application cost is a bargain compared to cleaning up oversized grass.

There are a number of variations on the Stam 3+ 3 program. One rule says use a quart of Stam for every leaf you have on your grass weeds. Labeled rates go up to 5 quarts per acre in a single application and it can help control large grasses, but remember when most of your grass is 5 leaf some of it is 6 and 7 leaf. The 3 quart at 2-3 leaf grass is probably the most economical timing.

Another rule of thumb says, "Stam your rice every Monday until you run out of grass or money" While this actual use of this rule is rare- it contains some wisdom. If you spray every week, the grass is more likely to be in the 2-3 leaf stage. This is also referring to those situations where levees are not built and the flood is not established on time. While the "textbook" program covers a 20-day dry period, some farmers have 40+ days without a permanent flood when weather conspired against their levee building. Two Stam applications will not work with a 40-day preflood period.

The Stam label contains a number of important do's and don'ts. Stam doesn't work well when it's cold. The rule of thumb here: if you wear a jacket in the Morning- don't spray. When it get's too hot Stam works too good and can burn rice. Actually, a lot of growers like to see the rice burn because they know the Stam is working. Finally, Stam interacts with insecticides. While certain insecticides safen cotton to Command- Most insecticides do the opposite in rice and will cause propanil to kill rice. Insecticides turn off the enzyme which digests propanil in rice. Take care if you've had an insecticide in your sprayer or have sprayed insecticides on your rice or PLAN to spray insecticide on your rice.

We should talk briefly about Stam alternatives. One popular alternative is Arrosolo. Arrosolo contains both propanil and molinate or "Ordram". While Ordram can be used as a residual herbicide it does not last if it's not incorporated or if it's not sprayed into a permanent flood.. So Arrosolo has little residual benefit unless it's sprayed into the flood in a salvage situation- at which time you've probably already lost yield to weed competition. Another product is called Super Wham. There have been a lot of debates as to what makes Super Wham work differently. However, here is the very important bottom line: Arrosolo and Super Wham have both been demonstrated to have slightly better activity than regular propanil. Under typical field conditions, you might see this difference about one year out of five. However, those other four years, there's usually no difference. Our official recommendation is to use whatever product you like personally. We might even joke that you should choose your favorite color because these products come in bright green, white and red drums. All products work. We also need to mention that propanil comes in both liquid and dry forms! The issue of brand names has an important implication for Missouri. Our rice is typically a week or two later than Arkansas' and it's not uncommon to run out particular products- especially in years when farmers grow lots of rice. The most important bottom line is that you can feel comfortable using whatever propanil based product you can get. DO NOT delay your application because your dealer is out of your favorite color of propanil.

To wrap things up here's a complication: Stam 3 + 3 is no longer the most popular weed control program. More frequently growers tank mix a residual herbicide and attempt to have one-pass weed control. We'll discuss this in the next article.

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