Management of sheath blight disease of rice in relation to the population of the pathogen in soil

Abstract

Laboratory, pot and field experiments were carried out to study the role of various physical, chemical and biological factors on the management of sheath blight disease of rice caused by Rhizoctonia solani Kuhn. (Thanatephorus Cucumerlis (Frank) Donk). Populations of total fungi, bacteria and actinomycetes in soil were enumerated at different stages of growth of the crop in order to assess their role in reducing the intensity and incidence of sheath blight disease. Results of the investigation revealed that the pathogen can be managed by deeper ploughing followed by submergence of the soil for a minimum period of two months. Amendments like glyricidia leaves, rice husk, lime and non edible oil cakes of marotti, neem and punna were useful in reducing the severity and spread of the disease. Fungicides like carbendazim and ediphenphos and the herbicide benthiocarb were also efficient in managing the disease. Rotation of rice with crops like tapioca, banana and brinjal was also useful. It was seen that amendments stimulated the population of saprophytes like Trichoderma viride in soil which are antagonistic to R. solani resulting in a subsequent reduction in population of the pathogen. In spite of the reduction in severity and spread of the disease, grain and straw yields were not enhanced by the treatments. More elaborate field trials are to be undertaken before landing on any ultimate conclusion regarding the use of these practices as tools for disease management.