Institute for Plant Protection, NARO

SOP for the rice false smut disease was published

- Rice false smut disease will be controlled by using fertilizers and decision support system for timely spraying of fungicides -

Researchers of National Agriculture and Food Research Organization (NARO) developed an effective control method which combined paddy soil mixing of converter slag or calcined lime before rice plantings, and use of a decision support system (1-km mesh agricultural weather data version) to timely control the rice false smut disease at panicle initiation stage. This will be effective to control with appropriate period of spraying fungicides against the disease. The standard operating procedure (SOP) manual was published on June 29, 2021.


Rice false smut disease caused by a fungus Villosiclava virens affects rice yield and grain quality. Pieces of the smut balls contaminated in brown rice will be considered unmarketable by Japanese agricultural standard rule. Until now, the disease is difficult to control because decision support system has not been used for timely spraying of fungicides. NARO developed an integrated control methods and published the SOP on website (Japanese only).

The false smut balls containing abundant chlamydospores fall onto paddy soil and become initial inoculum sources. Next year, the chlamydospores germinate and invade into rice roots of seedlings planted in the paddy fields. Because chlamydospores in the soil survive for several years, chemical control is needed at least three years. However, the effective application period is limited to 10 to 21 days before rice headings, determination of the appropriate timing of the fungicides has been difficult by farmers.

To solve this problem, NARO researchers developed a soil improvement method and a system for appropriate control of the disease and published the SOP manual. First, converter slag or calcined lime mixed into paddy soil method serves unfavorable condition against chlamydospores in the soil. Second, a decision support system using 1km-mesh agricultural weather data serves timely spraying of fungicides during appropriate period for suppression of the disease. The system delivers e-mails to support the total disease management. NARO expected that the disease control will become unnecessary within three years.

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