Kernel Smut Symptoms on Rice
Kernel Smut (fungus - Neovossia barclayana): This disease
causes losses in both yield and quality. The endosperm of the grain is attacked
by the fungus causing either part or all of the starchy material to be replaced by a black mass
of smut spores. The fungus does not destroy the seed embryo, and the diseased seed will
germinate even if all the endosperm has been replaced. Release of the smut spores from
within the kernel will cause a discoloration of hulls. Moisture causes the dark mass of
spores to swell and break out of the hull. Smut is easily detected after a rain or in the early
morning following a heavy dew. Kernel smut is usually most severe on late planted rice.
Usually, only a small percent of the kernels are affected, but monetary losses can be
significant because of penalties levied on the grain at the dryer. Milled rice has
a dull or grayish appearance when smutted grains are present in the sample. High rates of
nitrogen increase the incidence of smut. Varieties differ in the incidence of smut observed
in commercial plantings. Less smut is detected in most commercial semi-dwarf
varieties.
Control measures include the use of semi-dwarf varieties in fields with a history
of smut and to reduce reduce nitrogen rates and floodwater depths in fields where very
susceptible varieties must be grown. The fungicide propiconazole is effective in suppressing kernel smut.
February, 1996
