Intensive observations on the effect of some insecticides on Nephotettix virescens (Distant), a vector of virus and MLO diseases,with special reference to its transmission ability

The effects of some insecticides on Nephotettix virescens (Distant), a leafhopper vector of virus and MLO diseases, were studied with particular reference to their efficacy in affecting vector behaviour and transmission of rice tungro virus (RTV). When 10- and 15-day old seedlings from carbofuran-treated seeds were exposed to viruliferous vectors in cages, the percentages of transmission were 40 and 50, respectively against cent per cent in the control. Spraying of EC formulations of dimethoate, phosphamidon and methamidophos was not effective but decemethrin showed spectacular knockdown effect and gave absolute protection against RTV transmission upto 7 days. Since the transmission threshold of RTV is considerably shorter than of mycoplasmal diseases, the treatments affecting RTV transmission may reasonably be expected to be quite effective against MLO diseases like rice yellow dwarf and sandal spike, transmitted by N. virescens.