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Progress in sheath blight management in rice

Uma Shankar Singh: Intl Rice Research Inst - India Office

<div>Sheath blight disease, caused by <em>Rhizoctonia solani</em>, is the second most important rice disease worldwide after blast. It is particularly important when rice is grown intensively. In the lowland rice of tropical Asia average yield losses caused by sheath blight range from 5 to 10%. Host plant resistance represents a key approach for disease management. However, in the case of sheath blight, only quantitative (partial) resistance can be expected in rice, given the biology and wide host range of the pathogen. In spite of lot of efforts, so far no rice variety with a high level of resistance is deployed in Asia. Resistance inducing chemicals that are able to induce broad disease resistance offer an additional option for the farmer to complement genetic disease resistance/tolerance and the use of fungicides. Strobilurin based molecules like azoxystrobin, trifloxystrobin, metominostrobin has also been reported to manage the disease effectively and eco-friendly way than other commercially available fungicides. Efficacy of several fungicide combinations such as azoxystrobin plus difenconazole, kresoxim methyl plus hexaconazole, fluxapyroxad plus epixiconazole, trifloxystrobin plus tebuconazole, flutolanil plus azoxystrobin, thiophonate methyl plus azoxystrobin, tebuconazole plus azoxystrobin, propiconazole plus azoxystrobin against sheath blight have been reported. Thifluzamide is a member of the carboxamide class of fungicides which interfere with fungal respiration via their inhibitory effect on succinate dehydrogenase within the tricarboxylic acid cycle has been reported effective in managing sheath blight of rice. However, in case of heavy rains for longer period fungicide alone may not solve problem particularly if crop canopy is dense.</div>