False Smut of Rice | Symptoms & their management |

FALSE SMUT OF RICE

Causal Organism: Ustilaginoidea virens

Causal Organism according to old concept: Claviceps oryzae-sativa

Occurrence:-

·        It is occurs in almost all the rice growing areas of the world. In India losses due to the false smut have varied between 7% and 75%.

·          In Punjab loss varied between variety.

·        The loss in yield is not only due to the conversion of individual grains into smut balls but also due to increased sterility of neighboring florets. There is significant reduction in filled grains and spike weight.

Symptoms:-

·        Only few grains in a panicle are usually infected and the rest are normal. Effect of pathogen are visible only after flowering when parasite gro in ovary of individual kernals and transforms them into large, velvety, green ball which is more than twice the diameter of normal grains.

·        They gradually enlarge and become 1cm or more in diameter enclosing the floral parts.

·        Toung spore ball is flattened, smooth, light yellow in color and is covered by a membrane. Later, the membrane bursts. The color changes to orange, yellowish, green, olive green and finally to greenish black. Inside the ball, the color is orange yellow and nearly in while in center.

Identification of pathogen:-

Primary: Chalmydosphore

Secondary: Sclertia (Hard mass of ball)

Infection:-

Primary Source of Infection (PSI): Seed born inoculum

Secondary Source of Infection (SSI): Plant debris, Many grasses and wild rice

Epidemiology:-

·        Low temperature (20 degree celcius).

·        High relative humidity (>92%).

·        Moderate rainfall with intermittent clear and dizzling weather during flowering.

·        More prevalent in seasons favourable for good growth and high yields.

Management of disease:-

·        Use of disease- free  seeds that are selected from healthy crops.

·        Seed treatment with carbendazime 2.0g/kg of seeds and control insect- pest. Split application of nitrogen is recommended. Remove and proper disposal of infected plant debries.

·        Grow resistance variety and early planted crop has loss smut balls than the late planted crop.

·         Sprayingof cropper oxychloride@ 2.5g/ litre  or propiconazole@ 1.0ml/ litre at boat leaf and milky stage.

·        In area where the disease may cause yield loss, applying captan, captafol, fentin hydroxide and mancozeb can be inhibited conidial germination. Copper based fungicide can effectively control the disease.