Integration of fungal antagonist and organic amendments for the control of rice sheath blight

Sheath blight of rice caused by Rhizoctonia solani Kuhn is the disease of great importance all over the rice growing countries in the world. The disease offers a good example to illustrate the difficulties in controlling diseases caused by pathogens that are not host specific but are capable of causing serious damage under favourable environmental conditions. The disease is responsible for causing severe loss of 25-50% in yield from Philippines and Vietnam and 20-50% from Japan and 5.2-70% from India (9). Use of resistant cultivars has not been successful to control the disease because adequate level of host resistance has not been found. Fungicide application is effective but is limited to more affluent countries. The possible use of fungal antagonists of rice pathogen has been viewed as an alternative disease management strategy. Among the several antagonists tested by various scientists, Trichoderma spp. have been found effective in inhibiting the sheath blight of rice (R. solani) and extensively explored for the control of soil borne plant pathogens (6). Although, bioagent(s) have been found effective in inhibiting the growth of (R. solani) under in vitro condition, they fail to control the pathogen in field in most of the cases due to various reasons. It is because of the fact that biocontrol recommendations may hold promise under certain set of conditions only (especially under controlled conditions). Time of application, plant growth stages, the inocolum level and potential of pathogen as well as bioagents, mode and form of application or delivery system of the bioagent and integration of soil amendments etc. play vital role in biocontrol strategy. In the present investigation an attempt has been made to evaluate the effect of integration of organic amendments and fungal antagonist (T. harzianum) on sheath blight.