False smut — orange smut — is an irritating new rice disease for many of us in the South. It has spread throughout our production system since 1997. Depending on the year and conditions, the disease has been either very minor or very noticeable.

False smut primarily affects quality since the fungus produces brown “smut balls” that contaminate rice grain at harvest. These are unsightly and must be removed before the rice is used if there are very many of these balls within a load. It also can cause problems for exported rice.

We have worked on controlling this disease over the past few years in Arkansas and offer the following advice to farmers who do not particularly like false smut.

  1. Most varieties are susceptible although some varieties are less susceptible than others. We publish variety reactions to this disease each year in the Arkansas Rice Performance Test Report available from Extension county agents in our state. Try a less-susceptible variety in fields with a strong history of the problem.

  2. Early-planted rice has less of a problem with false smut than later-planted rice. So plant early if you can…. Duh! What is early? In our experience, anything planted in April has not had as much false smut as rice planted after about May 15.

  3. Ease off nitrogen fertilizer rates. Like kernel smut and most other rice diseases, false smut loves heavily fertilized rice. Fields with nitrogen rates above 160 pounds per acre tend to have the most false smut.

  4. While we do not have specific fungicide recommendations for this disease, we do have three years of data on the effectiveness of various rice fungicides. The most consistent and effective has been propiconazole, the active ingredient in Tilt or Propimax and one of the two fungicides in the new product, Stratego. When applied during the boot stage, all these products have reduced the number of smut balls in harvested grain by 50 to 75 percent, depending on the test. While not offering perfect control, this level of suppression can be pretty impressive when grain from untreated plots is compared to grain from treated plots. If you are already going to use propiconazole for kernel smut or if you have a serious history of false smut in a field, this fungicide should help out.

Rick Cartwright is an Extension plant pathologist with the University of Arkansas Division of Agriculture.