Texas Rice: Severe Outbreaks of Kernel Smut in 2021

Close up of rice kernel smut. Photo: Shane Zhou, Texas AgriLife Extension

Severe outbreaks of rice kernel smut, caused by the Tilletia horrida fungus, occurred across Texas. Smutted rice, which is characterized by replacement of rice grains with a black, sooth mass of smut spores, was observed in each of the rice fields surveyed in early August. Kernel smut widely occurred in the east and west areas of Houston, two major rice production areas in Texas.

Although the incidence of kernel smut varied with planting date, variety and location, smutted rice was found in each of the surveyed fields, with percent of panicles affected ranging from 0.5 to 50% and percent of kernels infected ranging from 0.1 to 20%. Thousands of acres of rice suffered from kernel smut, resulting in a significant reduction in rice yield and quality.

Total crop loss has seen on more than 20 acres of rice. All rice varieties, including hybrids and Provisia, were infected although kernel smut was more severe in inbreds than hybrids in general.

In addition, severe outbreaks of kernel smut were also observed on rice in southwest Louisiana.

The outbreaks of kernel smut across Texas apparently resulted from a historical record of continuous days of rain during the 30-day period of June 21 through July 21, which coincided with the rice flowering stage most susceptible to kernel smut infection.

The number of days with rain during this 30-day period was 23 and 15 days in the east and west Houston rice-producing areas, respectively. The total rainfall for that period was more than 10 inches in either rice-producing area.

Kernel smut, once considered as a minor disease, has become an emerging important disease in rice in Texas and other states over the past decade. A spike in kernel smut severity and the acreage affected this year further demonstrates its importance and threat to Texas rice production. Although kernel smut is difficult to control, timely and proper management of kernel smut is critical to reduce the damage caused by the disease.

  • Do not plant seed contaminated with smut spores
  • Plant rice varieties less susceptible to kernel smut
  • Plant early to avoid the conditions in the late season favorable for disease development
  • Avoid excessive nitrogen (N) fertilization with preferred rates less than 180 lbs N/acre
  • Timely apply with effective fungicides. Correct timing of fungicide applications is the key to the management of kernel smut. A fungicide application must be made at the mid-boot stage. An application made at the stage earlier than mid-boot or later than heading is less effective or ineffective. Under most conducive weather conditions such as this year’s weather, two applications are recommended. The 1st application should be made at the mid-boot stage followed by the 2nd application at heading. Propiconazole-containing fungicides such as Amistar Top, PropiMax, Quilt, QuiltXcell and Tilt are effective. Amistar Top is the only fungicide labeled for use in the ratoon (2nd) crop. Kernel smut can also occur on the ratoon crop. However, its severity is usually less than the severity on the main crop.

For more information about rice kernel smut and its management, please contact Dr. Shane Zhou at xzhou@aesrg.tamu.edu or (409) 752 2741 ext. 2225.




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