All India Coordinated Research Project on Tuber Crops; Cooperator-Voluntary Centre for Pathology Trials in Rice, DRR Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya, Kalyani-741235, India.
In India, during the early 1970s there was growing public attention about the extensive damage of Kharif (rainfed) rice crop due to severe rice tungro virus like symptoms. This concern was fuelled by the evidence for the epidemic out-breaks during 1967 to 1976 in some states of this country including West Bengal. The tungro monitoring reviewed here provides pandemic occurrence of this disease in Burdwan, Hooghly and Malda districts of this state during 1990s and re-emerging in 2001 caused considerable damage of the crop. The reported evidence established the gradual spreads of the tungro in cyclic pattern among the states in southern India. Our studies during the recent past revealed that declining field population of the vector, Green Leaf Hopper (GLH), (Nephotettix virescens) in summer would be the major reason for sporadic appearance of tungro. The ratoon plants regenerating from stubbles of infected Kharif rice have been found high transmission efficiency of tungro in susceptible varieties. Over the past 30 years, the epidemiological and ecological studies on the components of tungro epidemics in West Bengal revealed that intensification of agriculture, multiple cropping, new rice hybrids, increasing summer temperature with intermittent rains have positive correlation with fluctuation of GLH population and sporadic appearance of tungro. In the end, knowledge gained from the studies revealed that there is an urgent need of probabilistic analysis on input parameters whether resurgence of rice tungro virus would occur in present form or in modified form of epidemics in West Bengal.
