Use of cypermethrin, a synthetic pyrethroid, in the control of rice tungro virus disease and its vector

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Abstract
Out of 27 emulsifiable concentrate insecticides tested in the glasshouse, cypermethrin, vamidothion, FMC 35001, phosphamidon and demeton‐S‐methyl not only effectively prevented tungro virus infection but also killed the vector Nephotettix virescens (Dist.). Although dichlorvos, phosalone and phenthoate killed the vector efficiently they failed to prevent virus infection. Of the seven selected insecticides tested under field conditions, using Taichung (Native) 1 and Ratna as test cultivars, cypermethrin controlled tungro disease very efficiently and reduced the rate of tungro infection in the susceptible cultivar Taichung (Native) 1. Plant height, panicle number, grain yield and dry straw weight increased several fold in the cypermethrin‐treated plots in comparison to the control and other insecticides. Cypermethrin, acephate, FMC 35001, phosphamidon and demeton‐S‐methyl were very effective in controlling tungro disease and increased grain yield in Ratna, the tolerant cultivar. The vector population, both adult and nymph, was efficiently controlled by these insecticides in the respective rice cultivars. There was a strong negative correlation between the rate of tungro infection and plant height, panicle number, grain yield and dry straw weight and a positive correlation between vector population and the rate of tungro infection.