| Zusammenfassung: | Rice sheath blight caused by Rhizoctonia solani Kühn has been widely
distributed at rice growing areas in Central Java and Yogyakarta provinces. The
disease develops well in lowland rice field (0�200 m above sea level) and
develops more severe on semidwarf high yielding rice varieties. Increasing
degree of disease severity is correlated not only with increasing temperature and
relative humidity under plant canopy but also with decreasing conductivity and
soil pH. Sclerotia and mycelia of R. solani were widely spreaded in the rice
field might play a major role as primary inocula of sheath blight disease, should
be considered to control the disease which oriented to the density and potency
of initial inoculum. In the same niche, R. solani interacted with other soil
microorganisms, resulted in depressing growth or even death of R. solani.
Isolated antagonistic bacteria from soil surface containing organic matter were
able to suppress vegetative growth of R. solani as high as 46.5% in potato agar
medium and suppressed sheath blight lesion as high as 80.3% in vitro test.
Management of organic matter particularly mature compost could suppress the
disease. Mature compost suppressed sclerotial germinations of R. solani for
about 14.0% and improving mature compost with bacterial antagonistic
suppressed sclerotial germinations about 28.0%. In contrast, amending substrate
by fresh organic matter triggered R. solani to grow. Tall type and low-tillering
rice plant like Cimelati variety showed reducing effect on disease severity of
sheath blight. Cimelati phenotype caused environmental conditions under plant
canopy as temperature and relative humidity were lower than condition on
Ciherang and hybrid rice of Maro. This microclimate was not favorable for
sheath blight development. Relative humidity under plant canopy decreased
about 2.8% and 4.4%, in bed flooding irrigation arounded canal and bed
irrigation once a week, respectively. Integration of Cimelati rice variety and
uncontinuous flooding irrigation was effective for decreasing disease severity of
rice sheath blight. Sheath blight control by integration of some epidemic
components has a high chance of success to suppress the disease severity.
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