Rice is affected by four virus diseases in India. Of these, tungro is very widespread and reported from 11 states of India. Next to tungro disease, grassy stunt is important. But it is confined to South India only.
Recently a new strain of grassy stunt, GSV₄ has been reported from South India. The two other virus diseases, ragged stunt and necrotic mosaic are of minor importance and reported only from experimental farms. The significant contributions to tungro in India are on perpetuation of the virus and vectors, epidemiology and control of the disease. Tungro perpetuates on rice stubbles, wild rice species and a few grassy weeds. Artificial simulation of tungro epiphytotic conditions in experimental farms has been developed in India and a large number of rice germplasm has been screened.
Several resistance sources have been identified. A greater progress has been made on vector control. A synthetic pyrethroid, cypermethrin has been reported for effective control of the vector and prevention of tungro disease. Sources of resistance to grassy stunt have been identified. The rice cultivar IR32 and a non cultivated rice species ,Oryza minuta have been reported to be resistant to grassy stunt.