Most Arkansas rice farmers agree — 2008 was a bad year for false smut. Hank Chaney, county agent in Prairie County, Ark., said, it “was the worst case of false smut I’ve had in years.” We received more calls about false smut in 2008 than any year since 1998, from county agents, growers and consultants across our state. False smut is a complex disease and confusion remains about its origin, nature, effects, and control.

YOUNG FALSE smut galls showing silvery outer skin and orange spores inside.

False smut disease is caused by a fungus that infects rice panicles and produces unsightly structures called spore balls or galls that contaminate the grain at harvest. It was first reported in Arkansas in 1997, but has been in the United States for many years. The galls cycle through colors from silvery-white to orange to olive to black.

According to David TeBeest, professor with the University of Arkansas Department of Plant Pathology, false smut produces no symptoms prior to flowering, but during heading, the spore balls appear — making the disease harder to study and understand.

False smut, he says, is not a true smut (hence the name), but it may behave similarly to the true smuts in the way it infects and develops in the plant.

Currently, false smut has not been reported to cause heavy yield loss, although there is debate about this among scientists, growers and consultants because the disease also causes blanking. The biggest concern about false smut has been that the dark structures come off in the grain, causing unsightly contamination of concern to mills and importers in other countries where farmers may be wary of the disease spreading to their production areas.

Currently, the recommended methods to minimize false smut in Arkansas include:

1. Plant as early as possible (false smut is a disease of late maturing rice)

2. Use the correct amount of nitrogen fertilizer (do not apply excessive rates; this is especially important at the preflood timing).

3. Treat fields with propiconazole fungicide during the booting stages of rice. Once the rice starts to head, it’s too late. This suppresses the disease in most years, but did not seem to work as well in 2008, perhaps because of the cooler weather during heading, which slowed the grain maturity process.

4. Hybrids and medium grain rice varieties have been observed to be less susceptible under most conditions, although these observations have not always been consistent.

These practices will not guarantee a false smut free crop, but they should help.

David TeBeest and Steven Brooks (USDA/ARS, Dale Bumpers National Rice Research Center near Stuttgart, Ark.) are currently researching false smut. Brooks is cooperating on field studies with Merle Anders, systems agronomist at the Rice Research and Extension Center.

TeBeest and graduate students have adopted a method to detect DNA of the false smut fungus in infected rice plants, which helps speed up study of the disease. This has allowed them to study the effect of certain systemic fungicides, which may offer a new method of control when applied to the seed, but this needs to be further researched.

His group has established the seedborne and soilborne nature of false smut. Understanding this has led to the initial study of new control methods. Support for this work was provided directly by the University of Arkansas Division of Agriculture.

Brooks has been working on the nature of resistance in rice to both false smut and kernel smut, and notes that the most effective and economical control of such erratic diseases would be the development of improved high-yielding varieties or hybrids with durable and consistent resistance under the many growing conditions in the state and other parts of the South.

He is also working on understanding the effect of different growing conditions on the severity of both smut diseases. He has noted repeatedly that current hybrid rices have the most consistent resistance to kernel smut under a variety of conditions and further study is needed of the hybrids and false smut.

Brooks and Anders have noted many factors that influence false smut severity in their plots, including rotation, tillage method, and N fertility. Both scientists see the disease as an increasing problem in the region, but they remain confident that over time and with appropriate research support, they can make greater and more rapid progress to prevent the level of false smut observed in 2008 from re-occurring.